Clinical characteristics and risk factors for severe human metapneumovirus pneumonia in children: A single-center retrospective study

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Understanding the clinical characteristics and identifying risk factors of severe case is critical for timely intervention and improved clinical outcomes. Methods A retrospective study of children with HMPV pneumonia hospitalized in Guangzhou Women and Children’s Medical Center between January 2022 and December 2023 was performed. Binary logistic regression analysis was used to identify independent risk factors for severe HMPV pneumonia after univariate analysis. Results Our study included 159 patients (87 males and 72 females). Among them, 104 patients were in mild group and 55 in severe group. Compared to the mild group, children with severe pneumonia were younger, had a longer duration of fever, and more likely to present with wheezing, anemia (HGB 50mg/L), elevated level of LDH (LDH > 350U/L), hypoalbuminemia (ALB < 35g/L) as well as pulmonary consolidation/atelectasis (all p < 0.05). Furthermore, multivariate analysis shows that the independent risk factors associated with severe HMPV pneumonia in children were wheezing (OR = 18.233, CI: 5.559–59.807, p 50mg/L) (OR = 6.162, CI: 1.501–25.299, p = 0.012), elevated level of LDH (LDH > 350U/L) (OR = 3.514, CI: 1.202–10.275, p = 0.022) and pulmonary consolidation/atelectasis (OR = 13.836, CI: 1.646-116.299, p = 0.016). Conclusion Children with HMPV pneumonia who have wheezing, elevated level of CRP (CRP > 50mg/L), elevated level of LDH (LDH > 350U/L) or pulmonary consolidation/atelectasis are more easily developing to severe condition. Clinical trial number: Not applicable. Human metapneumovirus Severe pneumonia Clinical characteristics Risk factors Children Figures Figure 1 Figure 2 1 Introduction Human metapneumovirus (HMPV), first isolated from the nasopharyngeal secretions of children by Dutch scholars in 2001, is a significant respiratory pathogen which can lead to respiratory tract infections across all age groups[ 1 ]. It is a nonsegmented, negative-stranded RNA virus that belongs to the family Pneumoviridae. HMPV has one serotype with two genotypes( A and B). As an epidemic virus, HMPV shows seasonal variation during outbreaks, with the majority of infections being observed from late winter to spring[ 2 ]. HMPV infections typically manifest as mild and self-limiting respiratory illnesses and are often characterized by upper respiratory infection symptoms such as fever, cough, nasal congestion, rhinorrhea, hoarseness, sore throat[ 3 ]. Some patients require hospitalization for bronchitis or pneumonia caused by HMPV infections. The annual rate of hospitalization associated with HMPV among children under 5 years of age in the United States is approximately 1 ~ 1.2 per 1000 children, and the rate is even higher among European children[ 4 ]. A small proportion of patients can progress to severe pneumonia, acute respiratory distress syndrome (ARDS) or multiple organ dysfunction, and even lead to death[ 5 ]. Moreover, previous study has documented that the mortality rate in children with severe HMPV infection can reach up to 9%[ 6 ]. Early identification of severe HMPV pneumonia and timely intervention can reduce the risk of poor prognosis and even death in children. This study retrospectively analyzed 159 children hospitalized for HMPV pneumonia, which aimed to identify the risk predictors for severe HMPV pneumonia in children, providing clinical evidence for the early identification of severe cases. 2 Methods 2.1 Case definition and identification This study enrolled 159 patients hospitalized with HMPV pneumonia at Guangzhou Women and Children's Medical Center, Guangzhou Medical University, from January 2022 to December 2023. The inclusion criteria were as follows: (1) Diagnosed with community acquired pneumonia(CAP)[ 7 ]. (2) Age > 1 month and < 18 years. (3) Evidence of HMPV infection based on HMPV positivity on multiplex polymerase chain reaction performed using nasopharyngeal swab, sputum, and bronchial alveolar lavage fluid sample. The exclusion criteria were as follows: (1) with a severe comorbidity of malignancy, severe organ dysfunction, autoimmune disease, and congenital/acquired immune deficiency. (2) incomplete medical record information. 2.2 Diagnostic criteria for severe pneumonia Children with HMPV pneumonia were diagnosed with severe disease if they met at least 1 major criterion or 2 minor criteria among following criteria[ 7 ]: ①Major criteria: invasive mechanical ventilation, fluid refractory shock, acute need for noninvasive positive pressure ventilation, and hypoxemia requiring fraction of inspired oxygen (FiO2) greater than the inspired concentration or flow feasible in the general care area. ②Minor criteria: respiratory rate greater than that recommended by the WHO classification for age; apnoea; increased laboured breathing (e.g., retractions, dyspnoea, nasal flaring, and grunting), PaO2/FiO2 ratio < 250, multilobar infiltrates, altered mental status, hypotension, presence of effusion, comorbid conditions, and unexplained metabolic acidosis. 2.3 Study design and data collection According to the severe disease diagnostic criteria, the enrolled children were categorized into severe group and mild group (Study flowchart see Fig. 1 ). Clinical data were collected from the patients’ medical records, including demographic characteristics, length of stay, clinical symptoms and signs, laboratory indices, co-infection pathogens, chest images, treatments and outcomes. 2.4 Statistical analysis Statistical analysis were performed using IBM SPSS (version 27.0) and GraphPad Prism (version 10.4.1) software. Categorical data of the research was represented by the number of cases (n) and percentage (%), adopting the chi-square test in inter-group comparison. Measurement data that conformed to non-normal distribution was represented by median (M) and interquartile range (IQR), adopting the Mann-Whitney test. Univariate analyses were performed to determine the risk factors significantly associated with severe HMPV pneumonia. To identify the independent risk factors, binary logistic regression analysis was performed. Statistical significance was set at p < 0.05. 3 Results 3.1 Baseline demographic characteristics The study was conducted on 159 children, including 104 in the mild group and 55 in the severe group. Among them, 54.72% are male and 45.28% are female, which the ratio of male to female was similar between the mild and severe groups, without a significant difference (p > 0.05). The median age at onset was 2 years, and the median age in the severe group was lower than that in the mild group, with a significant difference (p < 0.05) (see Table 1 ). Table 1 Demographic data and clinical features of mild and severe groups in children with HMPV pneumonia Variable Total (n = 159) Mild group (n = 104) Severe group (n = 55) P -value Demographic data Age, years M(IQR) 2 (1,3) 3 (1,4) 2 (0.75,3) 0.016 Male n(%) 87 (54.72) 55 (52.88) 32 (58.18) 0.523 Clinical symptoms Cough n(%) 159 (100.00) 104 (100.00) 55 (100.00) > 0.999 Fever n(%) 147 (92.45) 93 (89.42) 54 (98.18) 0.059 Fever duration, days M(IQR) 5 (3,6) 5 (3,6) 6 (4,7) 0.002 Nasal congestion/rhinorrhea n(%) 91 (57.23) 68 (65.38) 23 (41.82) 0.054 Wheezing n(%) 66 (41.51) 26 (25.00) 40 (72.73) 0.999 Clinical signs Crackles n(%) 144 (90.57) 90 (86.54) 54 (98.18) 0.053 Tachypnea n(%) 53 (33.33) 0 (0.00) 53 (96.36) < 0.001 Decreased breath sounds n(%) 5 (3.14) 0 (0.00) 5 (9.09) 0.004 3.2 Clinical manifestations Common clinical manifestations among patients with HMPV pneumonia included cough (100.00%), fever (92.45%), nasal congestion/rhinorrhea (57.23%) and wheezing (41.51%). The fever duration ranged from 0 to 19 days, and the median fever duration was 5 days. There was no significant difference in the incidence of fever between the mild and severe groups (p > 0.05). However, the median fever duration in the severe group was significantly longer than in the mild group (p 0.05). However, severe cases were more likely to wheeze than mild cases, and the difference was statistically significant (p < 0.05). Notably, 6 patients in our research (4 in the mild group and 2 in severe group), who exhibited convulsion in neurological symptoms, were all under 5 years old and occurred only once 2 days before the onset of fever, which were considered to febrile convulsion. On physical examination, crackles were present in the majority of patients (90.57%). Tachypnea was exclusively observed in the severe group (96.36%). Decreased breath sounds were observed in only 5 cases, all of whom were in the severe group (see Table 1 ). 3.3 Laboratory indices and chest images Regarding to laboratory indices, no statistically significant difference was observed between the mild and severe groups in terms of leukocytopenia (WBC 12*10 9 /L),thrombocytopenia (PLT 450*10 9 /L), elevated level of liver enzymes (ALT > 80U/L or AST > 100U/L), or prolonged coagulation times (p > 0.05). However, compared to the mild group, patients in the severe group exhibited a significantly higher prevalence of anemia (HGB 50mg/L), elevated level of LDH (LDH > 350U/L), and hypoalbuminemia (ALB < 35g/L), with statistically significant differences (p 0.05) (see Table 2 ). All patients underwent chest X-ray or high-resolution computed tomography (HRCT) after admission. The most frequent manifestation was scattered patchy opacities (83.02%), other less frequent included consolidation/atelectasis (10.06%), mosaic attenuation (5.66%) and pleural effusion (3.14%). The incidence of pleural effusion and pulmonary consolidation/atelectasis was higher in the severe group compared to mild group, with statistically significant differences (p < 0.05) (see Table 3 ). The chest HRCT scans in children with HMPV pneumonia shown in Fig. 2 . Table 2 Laboratory indices of mild and severe groups in children with HMPV pneumonia Variable Total (n = 159) Mild group (n = 104) Severe group (n = 55) P -value Blood routine Leukocytopenia (WBC 12*10 9 /L) n(%) 45 (28.30) 29 (27.88) 16 (29.09) 0.872 Anemia (HGB < 90g/L) n(%) 9 (5.66) 0(0.00) 9 (16.36) < 0.001 Thrombocytopenia (PLT 450*10 9 /L) n(%) 16 (10.06) 11 (10.58) 5 (9.09) 0.767 Organ function CRP > 50mg/L n(%) 24 (15.09) 8 (7.69) 16 (29.09) 350U/L n(%) 81 (50.94) 44 (42.31) 37 (67.27) 0.003 ALT > 80U/L n(%) 6 (3.77) 2 (1.92) 4 (7.27) 0.183 AST > 100U/L n(%) 7 (4.40) 2 (1.92) 5 (9.09) 0.091 ALB < 35g/L n(%) 10 (6.29) 0 (0.00) 10 (18.18) 15S n(%) 6 (3.77) 2 (1.92) 4 (7.27) 0.213 APTT > 45S n(%) 29 (18.24) 14 (13.46) 15 (27.27) 0.054 FIB > 4g/L n(%) 58 (36.48) 33 (31.73) 25 (45.45) 0.087 Co-infection Other viruses n(%) 21 (13.21) 12 (11.54) 9 (16.36) 0.393 Bacterium n(%) 9 (5.66) 3 (2.88) 6 (10.91) 0.085 Mycoplasma pneumoniae n(%) 26 (16.35) 19 (18.27) 7 (12.73) 0.369 Abbreviations : WBC: White blood cell count; HGB: Hemoglobin; PLT: Platelet; CRP: C-reactive protein; LDH: Lactate dehydrogenase; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; ALB: Albumin; PT: Prothrombin time; APTT: Activated partial thromboplastin time; FIB: Fibrinogen. Table 3 C hest imaging of mild and severe groups in children with HMPV pneumonia Variable Total (n = 159) Mild group (n = 104) Severe group (n = 55) P -value Scattered patchy opacities n(%) 132 (83.02) 82 (78.85) 50 (90.91) 0.088 Pulmonary consolidation/ atelectasis n(%) 16 (10.06) 2 (1.92) 14 (25.45) < 0.001 Mosaic attenuation n(%) 9 (5.66) 4 (3.85) 5 (9.09) 0.277 Pleural effusion n(%) 5 (3.14) 0 (0.00) 5 (9.09) 0.004 3.4 Treatments and outcomes Compared to the mild group, the utilization rates of systemic corticosteroid and intravenous immunoglobulin therapy were significantly higher in the severe group (p < 0.05). In regard to respiratory support, most patients in the severe group received conventional oxygen therapy (92.73%), while a smaller proportion required non-invasive ventilation (18.18%) or invasive mechanical ventilation (20.00%). In term of outcomes, the median length of hospitalization in the severe group was significantly longer than in mild group (p < 0.05). Of the 55 patients with severe HMPV pneumonia, 22 were transferred to the ICU during hospitalization (40.00%). Notably, no fatal cases occurred among all patients included in the study (see Table 4 ). Table 4 Treatments and outcomes of mild and severe groups in children with HMPV pneumonia Variable Total (n = 159) Mild group (n = 104) Severe group (n = 55) P -value Treatments Systemic corticosteroid n(%) 49 (30.82) 12 (11.54) 37 (67.27) < 0.001 Intravenous Immunoglobulin n(%) 42 (26.42) 1 (0.96) 41(74.55) < 0.001 Bronchoscopy n(%) 11 (6.92) 1 (0.96) 10 (18.18) < 0.001 Oxygen therapy n(%) 51 (32.08) 0 (0.00) 51 (92.73) < 0.001 Non-invasive ventilation n(%) 10 (6.29) 0 (0.00) 10 (18.18) < 0.001 Invasive mechanical ventilation n(%) 11 (6.92) 0 (0.00) 11 (20.00) < 0.001 Outcomes Length of hospitalization, days M (IQR) 7 (5,9) 6 (4,7) 9 (7,12) < 0.001 Admission to ICU n(%) 22 (13.84) 0 (0.00) 22 (40.00) 0.999 3.5 Risk factors for severe HMPV pneumonia in children Besides tachypnea and pleural effusion, as minor criteria of severe pneumonia, we included the indicators having statistically significant differences between mild and severe groups in the binary logistic regression analysis, like age, fever duration, wheezing, decreased breath sounds, CRP > 50mg/L, LDH > 350U/L, HGB < 90g/L, ALB < 35g/L and pulmonary consolidation/atelectasis. The results shown that wheezing (OR = 18.233, CI: 5.559–59.807, p 50mg/L) (OR = 6.162, CI: 1.501–25.299, p = 0.012), elevated level of LDH (LDH > 350U/L) (OR = 3.514, CI: 1.202–10.275, p = 0.022), and images finding of pulmonary consolidation/atelectasis (OR = 13.836, CI: 1.646-116.299, p = 0.016) were independent risk factors for severe HMPV pneumonia in children (see Table 5 ). Table 5 Logistic regression analysis of severe risk factors for children with HMPV pneumonia Variables B P OR 95%CI Wheezing 2.903 50mg/L 1.818 0.012 6.162 1.501–25.299 LDH > 350U/L 1.257 0.022 3.514 1.202–10.275 Pulmonary consolidation/atelectasis 2.627 0.016 13.836 1.646-116.299 4 Discussion Infection with HMPV represents a considerable cause of respiratory infections in children, leading to an increase in hospitalization rate and healthcare burden[ 8 ]. Infection typically occurs early in life. The majority of cases affect children under five years of age and serological evidence indicates that most individuals have been infected by HMPV before the age of two[ 9 ]. Similarly, the median age of children with HMPV pneumonia in our study was 2 years and the severe group were younger than the mild group. No specific clinical symptoms in children with HMPV pneumonia. Despite the absence of mortality in our study, the ICU admission rate of 13.84% remains a significant concern. To identify severe cases at an early stage, we identified the independent risk factors for severe HMPV pneumonia, including wheezing, elevated level of CRP (CRP > 50mg/L), elevated level of LDH (LDH > 350U/L) and pulmonary consolidation/atelectasis. Wheezing is an adventitious sound produced by turbulent airflow during inhalation or exhalation due to narrowing or partial obstruction of the airways[ 10 ]. When respiratory infections occur, airway mucosal edema, mucus hypersecretion and airway hyperresponsiveness all contribute to the occurrence of wheezing[ 11 ]. Viruses that commonly cause wheezing in children are primarily respiratory syncytial virus and adenovirus, while other viruses, such as bocavirus, metapneumovirus, can also induce wheezing[ 12 , 13 ]. A multicenter study has demonstrated that wheezing is a risk factor for severe pneumonia[ 14 ]. Another study has also shown that wheezing is an independent risk factor for severe pneumonia caused by adenovirus or bocavirus[ 15 ]. In our study, wheezing was identified as an independent risk factor for severe HMPV pneumonia. Furthermore, previous research has shown that the HMPV A2b subtype is more frequently associated with wheezing compared to other genotypes, and children infected with the A2b subtype tend to have longer hospital stays[ 16 ]. However, our patients have not been tested for HMPV subtyping. Further investigations are warranted to explore the relationships between different HMPV subtypes and wheezing as well as disease severity. As an acute-phase reactant and a marker of systemic inflammation, CRP is widely used in clinical practice[ 17 ]. In current research, elevated level of CRP has been established as a risk factor for severe case not only in bacterial or Mycoplasma pneumoniae pneumonia, but also in viral (such as adenovirus and SARS-CoV-2) pneumonia[ 18 – 20 ]. Similarly, CRP > 50 mg/L was identified as an independent risk factor for severe HMPV pneumonia in our study. Previous studies have shown that the marked elevation of CRP may involve uncontrolled pulmonary inflammation activating systemic inflammatory pathways[ 21 ]. Specifically, during severe HMPV infection, viral proteins, such as G proteins and SH proteins, activate host pattern recognition receptors, promoting massive release of pro-inflammatory cytokines which circulate to the liver and stimulate hepatocytes to synthesize CRP, resulting in significantly increased serum CRP level[ 22 , 23 ]. Furthermore, the sharp rise in CRP is not only triggered by the viral proteins themselves but also stems from ongoing pulmonary tissue damage. As the airway infection progresses, necrotic and sloughed alveolar epithelial cells release damage-associated molecular patterns (DAMPs), such as high-mobility group box-1 (HMGB-1) and ATP[ 24 ]. These molecules activate relevant receptors on macrophages, further promote the release of cytokines, like IL-6, TNF-α and so on, thereby providing a sustained signal for CRP synthesis[ 25 ]. Therefore, it is understandable that elevated level of CRP serves as a risk factor for severe HMPV pneumonia. LDH is another commonly used clinical biomarker[ 26 ]. Its elevation as a risk factor for severe HMPV pneumonia in children is consistent with previous study[ 27 ]. LDH is a cytosolic enzyme widely present in human cells, and under normal conditions, its concentration in the blood is very low[ 28 ]. In severe infections, however, the most significant cause of elevated LDH is the necrosis of alveolar epithelial cells resulting from direct injury by pathogen[ 22 ]. Furthermore, severe infection indicates a more intense inflammatory factor storm, which also breaches the alveolar epithelium as well as cause necrosis of interstitial lung cells and vascular endothelial cells, contributing to the sharp increase in LDH level[ 29 ]. Therefore, LDH serves not only as a direct biomarker of pneumonia-induced tissue damage but also as an indirect indicator of excessive and dysregulated inflammatory responses, thereby constituting a valuable tool for clinical assessment of disease severity and risk stratification in patient management. In previous studies, bronchial wall thickening (70%-80%), scattered patchy opacities (78.6%-93.4%) and pulmonary hyperinflation (60%) have been documented as common imaging manifestations of HMPV pneumonia in children[ 30 , 31 ]. In our study, chest imaging findings were predominantly characterized by scattered patchy opacities, along with pulmonary consolidation/atelectasis and mosaic attenuation in a minority of cases. Notably, pulmonary consolidation/atelectasis was observed primarily in severe cases, accounting for approximately one-quarter of these patients. In reality, HMPV-damaged airway epithelium releases inflammatory mediators (e.g., IL-6, TNF-α, IL-18 and so on), which not only recruit immune cells, such as neutrophils and monocytes, to the airways but also diffuse into the alveolar interstitium via the airway-alveolar pathway[ 25 ]. It leads to congestion and edema of the alveolar walls, resulting in inflammatory exudation (predominantly serous, unlike purulent exudates in bacterial infections) within the alveolar spaces[ 32 ]. Such serous exudate, combined with mucus accumulation, may contribute to consolidation or atelectasis[ 33 ]. Consequently, HMPV infection does not merely cause airway inflammation, but rather induces progressive damage extending from the airway epithelium through the pulmonary interstitium to the lung parenchyma. Pulmonary consolidation/atelectasis represents the ultimate imaging manifestation of this injury cascade and serves as a more visualizable risk factor. Additionally, children with pneumonia who have mosaic attenuation on their imaging often present with wheezing, which may be associated with severe cases[ 34 ]. However, in our study, we did not find that mosaic attenuation were a risk factor for severe cases, maybe due to the insufficient sample size and low incidence.The relationship between them could be explored by increasing the sample size in the future. There are several limitations in the study. Firstly, we did not assess the specific genotypes of HMPV that may influence disease severity. Secondly, there was a lack of testing or dynamic monitoring of inflammatory markers (such as various cytokines) which could reflect changes in the patient's inflammatory storm. Thirdly, due to the small sample size, we were unable to perform stratified analyses across different age groups. 5 Conclusion In summary, children with HMPV pneumonia who have wheezing, elevated level of CRP (CRP > 50mg/L), elevated level of LDH (LDH > 350U/L) or pulmonary consolidation/atelectasis are more easily developing to severe condition. Early identification may be effectively reduce the risk of progression to severe illness. Declarations Ethics approval and consent to participate This study was performed in compliance with the principles of the Declaration of Helsinki and received approval from the Ethics Committee of Guangzhou Women and Children’s Medical Center, Guangzhou Medical University. Written informed consent was obtained from all participants or their legal guardians for the use of clinical and laboratory data extracted from the medical records. Consent for publication All authors have accepted responsibility for the entire content of this manuscript and approved its submission. Competing interest The authors declare that they have no competing interests. Funding This work was supported by the National Natural Science Foundation of China [grant No. 82370015 to G.L]. Author Contribution GL and SZ performed the study design and critical revision. XH and SZ wrote the manuscript. DQ, HF and DY collected the data. TT and DZ analyzed the data. All authors contributed to the article and approved the submitted version. Acknowledgement We are very appreciative to the children and their families. We also thank the editor and reviewers for relevant and helpful comments on the manuscript. Data Availability The full data and materials can be obtained from Dr. Lu (Gen Lu) upon sufficient and reasonable request. References Panda S, Mohakud NK, Pena L, et al. Human metapneumovirus: review of an important respiratory pathogen. 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Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 13 Feb, 2026 Reviewers agreed at journal 04 Feb, 2026 Reviewers invited by journal 20 Jan, 2026 Editor invited by journal 29 Dec, 2025 Editor assigned by journal 27 Dec, 2025 Submission checks completed at journal 27 Dec, 2025 First submitted to journal 23 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8434075","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":577922679,"identity":"98e96a96-18dc-4927-ae41-883152d9db3e","order_by":0,"name":"Shun Zhu","email":"","orcid":"","institution":"Guangzhou Women and Children's Medical Center, Guangzhou Medical University","correspondingAuthor":false,"prefix":"","firstName":"Shun","middleName":"","lastName":"Zhu","suffix":""},{"id":577922680,"identity":"7728aa2c-9323-4a2c-b149-6ec26488403b","order_by":1,"name":"Xue-Hua Xu","email":"","orcid":"","institution":"Guangzhou Women and 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11:41:50","extension":"html","order_by":22,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":153152,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8434075/v1/180a6cc31204a2f85a4d071a.html"},{"id":100884125,"identity":"5c24151c-9939-4c47-9f94-45cb2edb4e5b","added_by":"auto","created_at":"2026-01-22 11:42:07","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":112917,"visible":true,"origin":"","legend":"\u003cp\u003eStudy flowchart\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8434075/v1/3a42216a3bf8ed201d126f31.jpg"},{"id":100884084,"identity":"11b6bd43-86d9-4b63-9bf7-68b0d56c67e7","added_by":"auto","created_at":"2026-01-22 11:42:04","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":163942,"visible":true,"origin":"","legend":"\u003cp\u003eHigh-resolution computed tomography (HRCT) scans in children with HMPV pneumonia: (a) HRCT of a 4-year-old female patient with HMPV pneumonia shows extensive consolidation in the left upper lobe, with air bronchogram sign within the consolidated area. (b) HRCT of a 7-month-old female patient with HMPV pneumonia demonstrates mosaic attenuation in both lungs, more pronounced on the right side.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8434075/v1/1eb0a09cdcefbaaaaddd52c1.jpg"},{"id":101297013,"identity":"280e7c57-8cad-469b-b086-6e15634d27a0","added_by":"auto","created_at":"2026-01-28 09:24:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1326612,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8434075/v1/6cfaf31b-4186-4050-91d5-2418a70959b7.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Clinical characteristics and risk factors for severe human metapneumovirus pneumonia in children: A single-center retrospective study","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eHuman metapneumovirus (HMPV), first isolated from the nasopharyngeal secretions of children by Dutch scholars in 2001, is a significant respiratory pathogen which can lead to respiratory tract infections across all age groups[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. It is a nonsegmented, negative-stranded RNA virus that belongs to the family Pneumoviridae. HMPV has one serotype with two genotypes( A and B). As an epidemic virus, HMPV shows seasonal variation during outbreaks, with the majority of infections being observed from late winter to spring[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. HMPV infections typically manifest as mild and self-limiting respiratory illnesses and are often characterized by upper respiratory infection symptoms such as fever, cough, nasal congestion, rhinorrhea, hoarseness, sore throat[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Some patients require hospitalization for bronchitis or pneumonia caused by HMPV infections. The annual rate of hospitalization associated with HMPV among children under 5 years of age in the United States is approximately 1\u0026thinsp;~\u0026thinsp;1.2 per 1000 children, and the rate is even higher among European children[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. A small proportion of patients can progress to severe pneumonia, acute respiratory distress syndrome (ARDS) or multiple organ dysfunction, and even lead to death[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Moreover, previous study has documented that the mortality rate in children with severe HMPV infection can reach up to 9%[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Early identification of severe HMPV pneumonia and timely intervention can reduce the risk of poor prognosis and even death in children.\u003c/p\u003e \u003cp\u003eThis study retrospectively analyzed 159 children hospitalized for HMPV pneumonia, which aimed to identify the risk predictors for severe HMPV pneumonia in children, providing clinical evidence for the early identification of severe cases.\u003c/p\u003e"},{"header":"2 Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Case definition and identification\u003c/h2\u003e \u003cp\u003eThis study enrolled 159 patients hospitalized with HMPV pneumonia at Guangzhou Women and Children's Medical Center, Guangzhou Medical University, from January 2022 to December 2023.\u003c/p\u003e \u003cp\u003eThe inclusion criteria were as follows:\u003c/p\u003e \u003cp\u003e(1) Diagnosed with community acquired pneumonia(CAP)[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e(2) Age\u0026thinsp;\u0026gt;\u0026thinsp;1 month and \u0026lt;\u0026thinsp;18 years.\u003c/p\u003e \u003cp\u003e(3) Evidence of HMPV infection based on HMPV positivity on multiplex polymerase chain reaction performed using nasopharyngeal swab, sputum, and bronchial alveolar lavage fluid sample.\u003c/p\u003e \u003cp\u003eThe exclusion criteria were as follows:\u003c/p\u003e \u003cp\u003e(1) with a severe comorbidity of malignancy, severe organ dysfunction, autoimmune disease, and congenital/acquired immune deficiency.\u003c/p\u003e \u003c/div\u003e\u003cp\u003e(2) incomplete medical record information.\u003c/p\u003e\u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Diagnostic criteria for severe pneumonia\u003c/h2\u003e \u003cp\u003eChildren with HMPV pneumonia were diagnosed with severe disease if they met at least 1 major criterion or 2 minor criteria among following criteria[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]:\u003c/p\u003e \u003cp\u003e①Major criteria: invasive mechanical ventilation, fluid refractory shock, acute need for noninvasive positive pressure ventilation, and hypoxemia requiring fraction of inspired oxygen (FiO2) greater than the inspired concentration or flow feasible in the general care area.\u003c/p\u003e \u003cp\u003e②Minor criteria: respiratory rate greater than that recommended by the WHO classification for age; apnoea; increased laboured breathing (e.g., retractions, dyspnoea, nasal flaring, and grunting), PaO2/FiO2 ratio\u0026thinsp;\u0026lt;\u0026thinsp;250, multilobar infiltrates, altered mental status, hypotension, presence of effusion, comorbid conditions, and unexplained metabolic acidosis.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Study design and data collection\u003c/h2\u003e \u003cp\u003eAccording to the severe disease diagnostic criteria, the enrolled children were categorized into severe group and mild group (Study flowchart see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Clinical data were collected from the patients\u0026rsquo; medical records, including demographic characteristics, length of stay, clinical symptoms and signs, laboratory indices, co-infection pathogens, chest images, treatments and outcomes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Statistical analysis\u003c/h2\u003e \u003cp\u003eStatistical analysis were performed using IBM SPSS (version 27.0) and GraphPad Prism (version 10.4.1) software. Categorical data of the research was represented by the number of cases (n) and percentage (%), adopting the chi-square test in inter-group comparison. Measurement data that conformed to non-normal distribution was represented by median (M) and interquartile range (IQR), adopting the Mann-Whitney test. Univariate analyses were performed to determine the risk factors significantly associated with severe HMPV pneumonia. To identify the independent risk factors, binary logistic regression analysis was performed. Statistical significance was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"3 Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Baseline demographic characteristics\u003c/h2\u003e \u003cp\u003eThe study was conducted on 159 children, including 104 in the mild group and 55 in the severe group. Among them, 54.72% are male and 45.28% are female, which the ratio of male to female was similar between the mild and severe groups, without a significant difference (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The median age at onset was 2 years, and the median age in the severe group was lower than that in the mild group, with a significant difference (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (see Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDemographic data and clinical features of mild and severe groups in children with HMPV pneumonia\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;159)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMild group\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;104)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSevere group (n\u0026thinsp;=\u0026thinsp;55)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDemographic data\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge, years M(IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2 (1,3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3 (1,4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2 (0.75,3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.016\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMale n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e87 (54.72)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e55 (52.88)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e32 (58.18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.523\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eClinical symptoms\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCough n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e159 (100.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e104 (100.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e55 (100.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;0.999\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFever n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e147 (92.45)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e93 (89.42)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e54 (98.18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.059\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFever duration, days M(IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (3,6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5 (3,6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6 (4,7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.002\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNasal congestion/rhinorrhea n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e91 (57.23)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e68 (65.38)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e23 (41.82)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.054\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWheezing n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e66 (41.51)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e26 (25.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e40 (72.73)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGastrointestinal symptoms (vomit/diarrhoea) n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24 (15.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 (11.54)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12 (21.82)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.085\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNeurological symptoms (convulsion/sleepiness/dysphoria) n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 (3.77)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4 (3.85)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2 (3.64)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;0.999\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eClinical signs\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCrackles n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e144 (90.57)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e90 (86.54)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e54 (98.18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.053\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTachypnea n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e53 (33.33)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e53 (96.36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDecreased breath sounds n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (3.14)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5 (9.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.004\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Clinical manifestations\u003c/h2\u003e \u003cp\u003eCommon clinical manifestations among patients with HMPV pneumonia included cough (100.00%), fever (92.45%), nasal congestion/rhinorrhea (57.23%) and wheezing (41.51%). The fever duration ranged from 0 to 19 days, and the median fever duration was 5 days. There was no significant difference in the incidence of fever between the mild and severe groups (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). However, the median fever duration in the severe group was significantly longer than in the mild group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Besides, there was no statistical difference in cough and nasal congestion/rhinorrhea between the severe group and mild group (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). However, severe cases were more likely to wheeze than mild cases, and the difference was statistically significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Notably, 6 patients in our research (4 in the mild group and 2 in severe group), who exhibited convulsion in neurological symptoms, were all under 5 years old and occurred only once 2 days before the onset of fever, which were considered to febrile convulsion. On physical examination, crackles were present in the majority of patients (90.57%). Tachypnea was exclusively observed in the severe group (96.36%). Decreased breath sounds were observed in only 5 cases, all of whom were in the severe group (see Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Laboratory indices and chest images\u003c/h2\u003e \u003cp\u003eRegarding to laboratory indices, no statistically significant difference was observed between the mild and severe groups in terms of leukocytopenia (WBC\u0026thinsp;\u0026lt;\u0026thinsp;5*10\u003csup\u003e9\u003c/sup\u003e/L), leukocytosis (WBC\u0026thinsp;\u0026gt;\u0026thinsp;12*10\u003csup\u003e9\u003c/sup\u003e/L),thrombocytopenia (PLT\u0026thinsp;\u0026lt;\u0026thinsp;100*10\u003csup\u003e9\u003c/sup\u003e/L), thrombocytosis (PLT\u0026thinsp;\u0026gt;\u0026thinsp;450*10\u003csup\u003e9\u003c/sup\u003e/L), elevated level of liver enzymes (ALT\u0026thinsp;\u0026gt;\u0026thinsp;80U/L or AST\u0026thinsp;\u0026gt;\u0026thinsp;100U/L), or prolonged coagulation times (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). However, compared to the mild group, patients in the severe group exhibited a significantly higher prevalence of anemia (HGB\u0026thinsp;\u0026lt;\u0026thinsp;90g/L), elevated level of CRP (CRP\u0026thinsp;\u0026gt;\u0026thinsp;50mg/L), elevated level of LDH (LDH\u0026thinsp;\u0026gt;\u0026thinsp;350U/L), and hypoalbuminemia (ALB\u0026thinsp;\u0026lt;\u0026thinsp;35g/L), with statistically significant differences (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). As for etiological findings, there was no statistical difference in co-infections with other viruses, bacteria or Mycoplasma pneumoniae between the mild and severe groups (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (see Table \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). All patients underwent chest X-ray or high-resolution computed tomography (HRCT) after admission. The most frequent manifestation was scattered patchy opacities (83.02%), other less frequent included consolidation/atelectasis (10.06%), mosaic attenuation (5.66%) and pleural effusion (3.14%). The incidence of pleural effusion and pulmonary consolidation/atelectasis was higher in the severe group compared to mild group, with statistically significant differences (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (see Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The chest HRCT scans in children with HMPV pneumonia shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLaboratory indices of mild and severe groups in children with HMPV pneumonia\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;159)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMild group\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;104)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSevere group (n\u0026thinsp;=\u0026thinsp;55)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBlood routine\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLeukocytopenia\u003c/p\u003e \u003cp\u003e(WBC\u0026thinsp;\u0026lt;\u0026thinsp;5*10\u003csup\u003e9\u003c/sup\u003e/L) n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e32 (20.13)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e23 (22.12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e9 (16.36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.390\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLeukocytosis\u003c/p\u003e \u003cp\u003e(WBC\u0026thinsp;\u0026gt;\u0026thinsp;12*10\u003csup\u003e9\u003c/sup\u003e/L) n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e45 (28.30)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e29 (27.88)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e16 (29.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.872\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnemia (HGB\u0026thinsp;\u0026lt;\u0026thinsp;90g/L) n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9 (5.66)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0(0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e9 (16.36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThrombocytopenia\u003c/p\u003e \u003cp\u003e(PLT\u0026thinsp;\u0026lt;\u0026thinsp;100*10\u003csup\u003e9\u003c/sup\u003e/L) n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4 (2.52)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1 (0.96)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3 (5.45)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.235\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThrombocytosis (PLT\u0026thinsp;\u0026gt;\u0026thinsp;450*10\u003csup\u003e9\u003c/sup\u003e/L) n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e16 (10.06)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11 (10.58)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5 (9.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.767\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOrgan function\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCRP\u0026thinsp;\u0026gt;\u0026thinsp;50mg/L n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e24 (15.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8 (7.69)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e16 (29.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLDH\u0026thinsp;\u0026gt;\u0026thinsp;350U/L n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e81 (50.94)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e44 (42.31)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e37 (67.27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.003\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eALT\u0026thinsp;\u0026gt;\u0026thinsp;80U/L n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6 (3.77)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2 (1.92)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4 (7.27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.183\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAST\u0026thinsp;\u0026gt;\u0026thinsp;100U/L n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7 (4.40)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2 (1.92)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5 (9.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.091\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eALB\u0026thinsp;\u0026lt;\u0026thinsp;35g/L n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e10 (6.29)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e10 (18.18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCoagulation function\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePT\u0026thinsp;\u0026gt;\u0026thinsp;15S n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6 (3.77)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2 (1.92)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4 (7.27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.213\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAPTT\u0026thinsp;\u0026gt;\u0026thinsp;45S n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e29 (18.24)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e14 (13.46)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e15 (27.27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.054\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFIB\u0026thinsp;\u0026gt;\u0026thinsp;4g/L n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e58 (36.48)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e33 (31.73)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e25 (45.45)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.087\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCo-infection\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOther viruses n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e21 (13.21)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e12 (11.54)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e9 (16.36)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.393\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBacterium n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9 (5.66)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3 (2.88)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6 (10.91)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.085\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMycoplasma pneumoniae n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e26 (16.35)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e19 (18.27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7 (12.73)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.369\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u003cb\u003eAbbreviations\u003c/b\u003e: WBC: White blood cell count; HGB: Hemoglobin; PLT: Platelet; CRP: C-reactive protein; LDH: Lactate dehydrogenase; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; ALB: Albumin; PT: Prothrombin time; APTT: Activated partial thromboplastin time; FIB: Fibrinogen.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cb\u003eC\u003c/b\u003ehest imaging of mild and severe groups in children with HMPV pneumonia\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;159)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMild group\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;104)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSevere group (n\u0026thinsp;=\u0026thinsp;55)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eScattered patchy opacities n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e132 (83.02)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e82 (78.85)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e50 (90.91)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.088\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePulmonary consolidation/ atelectasis n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e16 (10.06)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2 (1.92)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e14 (25.45)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMosaic attenuation n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e9 (5.66)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e4 (3.85)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5 (9.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.277\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePleural effusion n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5 (3.14)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5 (9.09)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.004\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Treatments and outcomes\u003c/h2\u003e \u003cp\u003eCompared to the mild group, the utilization rates of systemic corticosteroid and intravenous immunoglobulin therapy were significantly higher in the severe group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In regard to respiratory support, most patients in the severe group received conventional oxygen therapy (92.73%), while a smaller proportion required non-invasive ventilation (18.18%) or invasive mechanical ventilation (20.00%). In term of outcomes, the median length of hospitalization in the severe group was significantly longer than in mild group (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Of the 55 patients with severe HMPV pneumonia, 22 were transferred to the ICU during hospitalization (40.00%). Notably, no fatal cases occurred among all patients included in the study (see Table \u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eTreatments and outcomes of mild and severe groups in children with HMPV pneumonia\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;159)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMild group\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;104)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSevere group (n\u0026thinsp;=\u0026thinsp;55)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTreatments\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSystemic corticosteroid n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e49 (30.82)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 (11.54)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e37 (67.27)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIntravenous Immunoglobulin n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e42 (26.42)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (0.96)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e41(74.55)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBronchoscopy n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11 (6.92)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (0.96)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10 (18.18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOxygen therapy n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e51 (32.08)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e51 (92.73)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNon-invasive ventilation n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 (6.29)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10 (18.18)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInvasive mechanical ventilation n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11 (6.92)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e11 (20.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eOutcomes\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLength of hospitalization, days M (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7 (5,9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6 (4,7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9 (7,12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdmission to ICU n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22 (13.84)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e22 (40.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMortality n(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0 (0.00)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;0.999\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Risk factors for severe HMPV pneumonia in children\u003c/h2\u003e \u003cp\u003eBesides tachypnea and pleural effusion, as minor criteria of severe pneumonia, we included the indicators having statistically significant differences between mild and severe groups in the binary logistic regression analysis, like age, fever duration, wheezing, decreased breath sounds, CRP\u0026thinsp;\u0026gt;\u0026thinsp;50mg/L, LDH\u0026thinsp;\u0026gt;\u0026thinsp;350U/L, HGB\u0026thinsp;\u0026lt;\u0026thinsp;90g/L, ALB\u0026thinsp;\u0026lt;\u0026thinsp;35g/L and pulmonary consolidation/atelectasis. The results shown that wheezing (OR\u0026thinsp;=\u0026thinsp;18.233, CI: 5.559\u0026ndash;59.807, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), elevated level of CRP (CRP\u0026thinsp;\u0026gt;\u0026thinsp;50mg/L) (OR\u0026thinsp;=\u0026thinsp;6.162, CI: 1.501\u0026ndash;25.299, p\u0026thinsp;=\u0026thinsp;0.012), elevated level of LDH (LDH\u0026thinsp;\u0026gt;\u0026thinsp;350U/L) (OR\u0026thinsp;=\u0026thinsp;3.514, CI: 1.202\u0026ndash;10.275, p\u0026thinsp;=\u0026thinsp;0.022), and images finding of pulmonary consolidation/atelectasis (OR\u0026thinsp;=\u0026thinsp;13.836, CI: 1.646-116.299, p\u0026thinsp;=\u0026thinsp;0.016) were independent risk factors for severe HMPV pneumonia in children (see Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eLogistic regression analysis of severe risk factors for children with HMPV pneumonia\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOR\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e95%CI\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWheezing\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.903\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e18.233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.559\u0026ndash;59.807\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCRP\u0026thinsp;\u0026gt;\u0026thinsp;50mg/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.818\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.012\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.162\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.501\u0026ndash;25.299\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLDH\u0026thinsp;\u0026gt;\u0026thinsp;350U/L\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.257\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.022\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.514\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.202\u0026ndash;10.275\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePulmonary consolidation/atelectasis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2.627\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.016\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e13.836\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.646-116.299\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4 Discussion","content":"\u003cp\u003eInfection with HMPV represents a considerable cause of respiratory infections in children, leading to an increase in hospitalization rate and healthcare burden[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Infection typically occurs early in life. The majority of cases affect children under five years of age and serological evidence indicates that most individuals have been infected by HMPV before the age of two[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Similarly, the median age of children with HMPV pneumonia in our study was 2 years and the severe group were younger than the mild group. No specific clinical symptoms in children with HMPV pneumonia. Despite the absence of mortality in our study, the ICU admission rate of 13.84% remains a significant concern. To identify severe cases at an early stage, we identified the independent risk factors for severe HMPV pneumonia, including wheezing, elevated level of CRP (CRP\u0026thinsp;\u0026gt;\u0026thinsp;50mg/L), elevated level of LDH (LDH\u0026thinsp;\u0026gt;\u0026thinsp;350U/L) and pulmonary consolidation/atelectasis.\u003c/p\u003e \u003cp\u003eWheezing is an adventitious sound produced by turbulent airflow during inhalation or exhalation due to narrowing or partial obstruction of the airways[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. When respiratory infections occur, airway mucosal edema, mucus hypersecretion and airway hyperresponsiveness all contribute to the occurrence of wheezing[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Viruses that commonly cause wheezing in children are primarily respiratory syncytial virus and adenovirus, while other viruses, such as bocavirus, metapneumovirus, can also induce wheezing[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. A multicenter study has demonstrated that wheezing is a risk factor for severe pneumonia[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Another study has also shown that wheezing is an independent risk factor for severe pneumonia caused by adenovirus or bocavirus[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In our study, wheezing was identified as an independent risk factor for severe HMPV pneumonia. Furthermore, previous research has shown that the HMPV A2b subtype is more frequently associated with wheezing compared to other genotypes, and children infected with the A2b subtype tend to have longer hospital stays[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. However, our patients have not been tested for HMPV subtyping. Further investigations are warranted to explore the relationships between different HMPV subtypes and wheezing as well as disease severity.\u003c/p\u003e \u003cp\u003eAs an acute-phase reactant and a marker of systemic inflammation, CRP is widely used in clinical practice[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. In current research, elevated level of CRP has been established as a risk factor for severe case not only in bacterial or Mycoplasma pneumoniae pneumonia, but also in viral (such as adenovirus and SARS-CoV-2) pneumonia[\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Similarly, CRP\u0026thinsp;\u0026gt;\u0026thinsp;50 mg/L was identified as an independent risk factor for severe HMPV pneumonia in our study. Previous studies have shown that the marked elevation of CRP may involve uncontrolled pulmonary inflammation activating systemic inflammatory pathways[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Specifically, during severe HMPV infection, viral proteins, such as G proteins and SH proteins, activate host pattern recognition receptors, promoting massive release of pro-inflammatory cytokines which circulate to the liver and stimulate hepatocytes to synthesize CRP, resulting in significantly increased serum CRP level[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Furthermore, the sharp rise in CRP is not only triggered by the viral proteins themselves but also stems from ongoing pulmonary tissue damage. As the airway infection progresses, necrotic and sloughed alveolar epithelial cells release damage-associated molecular patterns (DAMPs), such as high-mobility group box-1 (HMGB-1) and ATP[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. These molecules activate relevant receptors on macrophages, further promote the release of cytokines, like IL-6, TNF-α and so on, thereby providing a sustained signal for CRP synthesis[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Therefore, it is understandable that elevated level of CRP serves as a risk factor for severe HMPV pneumonia.\u003c/p\u003e \u003cp\u003eLDH is another commonly used clinical biomarker[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Its elevation as a risk factor for severe HMPV pneumonia in children is consistent with previous study[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. LDH is a cytosolic enzyme widely present in human cells, and under normal conditions, its concentration in the blood is very low[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. In severe infections, however, the most significant cause of elevated LDH is the necrosis of alveolar epithelial cells resulting from direct injury by pathogen[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Furthermore, severe infection indicates a more intense inflammatory factor storm, which also breaches the alveolar epithelium as well as cause necrosis of interstitial lung cells and vascular endothelial cells, contributing to the sharp increase in LDH level[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Therefore, LDH serves not only as a direct biomarker of pneumonia-induced tissue damage but also as an indirect indicator of excessive and dysregulated inflammatory responses, thereby constituting a valuable tool for clinical assessment of disease severity and risk stratification in patient management.\u003c/p\u003e \u003cp\u003eIn previous studies, bronchial wall thickening (70%-80%), scattered patchy opacities (78.6%-93.4%) and pulmonary hyperinflation (60%) have been documented as common imaging manifestations of HMPV pneumonia in children[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. In our study, chest imaging findings were predominantly characterized by scattered patchy opacities, along with pulmonary consolidation/atelectasis and mosaic attenuation in a minority of cases. Notably, pulmonary consolidation/atelectasis was observed primarily in severe cases, accounting for approximately one-quarter of these patients. In reality, HMPV-damaged airway epithelium releases inflammatory mediators (e.g., IL-6, TNF-α, IL-18 and so on), which not only recruit immune cells, such as neutrophils and monocytes, to the airways but also diffuse into the alveolar interstitium via the airway-alveolar pathway[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. It leads to congestion and edema of the alveolar walls, resulting in inflammatory exudation (predominantly serous, unlike purulent exudates in bacterial infections) within the alveolar spaces[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Such serous exudate, combined with mucus accumulation, may contribute to consolidation or atelectasis[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Consequently, HMPV infection does not merely cause airway inflammation, but rather induces progressive damage extending from the airway epithelium through the pulmonary interstitium to the lung parenchyma. Pulmonary consolidation/atelectasis represents the ultimate imaging manifestation of this injury cascade and serves as a more visualizable risk factor. Additionally, children with pneumonia who have mosaic attenuation on their imaging often present with wheezing, which may be associated with severe cases[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. However, in our study, we did not find that mosaic attenuation were a risk factor for severe cases, maybe due to the insufficient sample size and low incidence.The relationship between them could be explored by increasing the sample size in the future.\u003c/p\u003e \u003cp\u003eThere are several limitations in the study. Firstly, we did not assess the specific genotypes of HMPV that may influence disease severity. Secondly, there was a lack of testing or dynamic monitoring of inflammatory markers (such as various cytokines) which could reflect changes in the patient's inflammatory storm. Thirdly, due to the small sample size, we were unable to perform stratified analyses across different age groups.\u003c/p\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eIn summary, children with HMPV pneumonia who have wheezing, elevated level of CRP (CRP\u0026thinsp;\u0026gt;\u0026thinsp;50mg/L), elevated level of LDH (LDH\u0026thinsp;\u0026gt;\u0026thinsp;350U/L) or pulmonary consolidation/atelectasis are more easily developing to severe condition. Early identification may be effectively reduce the risk of progression to severe illness.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e \u003cp\u003e This study was performed in compliance with the principles of the Declaration of Helsinki and received approval from the Ethics Committee of Guangzhou Women and Children\u0026rsquo;s Medical Center, Guangzhou Medical University. Written informed consent was obtained from all participants or their legal guardians for the use of clinical and laboratory data extracted from the medical records.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003e All authors have accepted responsibility for the entire content of this manuscript and approved its submission.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interest\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e \u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis work was supported by the National Natural Science Foundation of China [grant No. 82370015 to G.L].\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eGL and SZ performed the study design and critical revision. XH and SZ wrote the manuscript. DQ, HF and DY collected the data. TT and DZ analyzed the data. All authors contributed to the article and approved the submitted version.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe are very appreciative to the children and their families. We also thank the editor and reviewers for relevant and helpful comments on the manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe full data and materials can be obtained from Dr. Lu (Gen Lu) upon sufficient and reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePanda S, Mohakud NK, Pena L, et al. Human metapneumovirus: review of an important respiratory pathogen. 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Pediatr Pulmonol. 2021;56(5):1069\u0026ndash;76. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1002/ppul.25220\u003c/span\u003e\u003cspan address=\"10.1002/ppul.25220\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-pulmonary-medicine","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pulm","sideBox":"Learn more about [BMC Pulmonary Medicine](http://bmcpulmmed.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pulm/default.aspx","title":"BMC Pulmonary Medicine","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Human metapneumovirus, Severe pneumonia, Clinical characteristics, Risk factors, Children","lastPublishedDoi":"10.21203/rs.3.rs-8434075/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8434075/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHuman metapneumovirus (HMPV) is an important etiological agent of pediatric acute respiratory tract infections, with the potential to cause severe pneumonia. Understanding the clinical characteristics and identifying risk factors of severe case is critical for timely intervention and improved clinical outcomes.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA retrospective study of children with HMPV pneumonia hospitalized in Guangzhou Women and Children’s Medical Center between January 2022 and December 2023 was performed. Binary logistic regression analysis was used to identify independent risk factors for severe HMPV pneumonia after univariate analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOur study included 159 patients (87 males and 72 females). Among them, 104 patients were in mild group and 55 in severe group. Compared to the mild group, children with severe pneumonia were younger, had a longer duration of fever, and more likely to present with wheezing, anemia (HGB \u0026lt; 90g/L), elevated level of CRP (CRP \u0026gt; 50mg/L), elevated level of LDH (LDH \u0026gt; 350U/L), hypoalbuminemia (ALB \u0026lt; 35g/L) as well as pulmonary consolidation/atelectasis (all p \u0026lt; 0.05). Furthermore, multivariate analysis shows that the independent risk factors associated with severe HMPV pneumonia in children were wheezing (OR = 18.233, CI: 5.559–59.807, p \u0026lt; 0.001), elevated level of CRP (CRP \u0026gt; 50mg/L) (OR = 6.162, CI: 1.501–25.299, p = 0.012), elevated level of LDH (LDH \u0026gt; 350U/L) (OR = 3.514, CI: 1.202–10.275, p = 0.022) and pulmonary consolidation/atelectasis (OR = 13.836, CI: 1.646-116.299, p = 0.016).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eChildren with HMPV pneumonia who have wheezing, elevated level of CRP (CRP \u0026gt; 50mg/L), elevated level of LDH (LDH \u0026gt; 350U/L) or pulmonary consolidation/atelectasis are more easily developing to severe condition.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number: \u003c/strong\u003eNot applicable.\u003c/p\u003e","manuscriptTitle":"Clinical characteristics and risk factors for severe human metapneumovirus pneumonia in children: A single-center retrospective study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-22 11:38:51","doi":"10.21203/rs.3.rs-8434075/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-02-13T11:30:25+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"319147785939566307895211071303607554580","date":"2026-02-04T11:16:52+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-20T14:26:01+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-12-29T11:49:21+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-27T13:23:44+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-27T13:23:30+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Pulmonary Medicine","date":"2025-12-23T12:51:08+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-pulmonary-medicine","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pulm","sideBox":"Learn more about [BMC Pulmonary Medicine](http://bmcpulmmed.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pulm/default.aspx","title":"BMC Pulmonary Medicine","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"be1eb4ba-c752-4a47-8afa-00912e0a9c49","owner":[],"postedDate":"January 22nd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-01-22T11:38:52+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-22 11:38:51","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8434075","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8434075","identity":"rs-8434075","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}