Dynamic trends of common pathogens associated pediatric lower respiratory tract infections in Beijing: 2017 to 2025

Lower respiratory tract infections (LRTIs) are one of the leading causes of hospitalization in children, with their associated respiratory pathogens typically following seasonal epidemic patterns. However, the COVID-19 pandemic has profoundly altered the landscape of pediatric respiratory infections, causing unprecedented shifts in the epidemiology of common respiratory pathogens. To date, long-term epidemiological surveillance remains limited, particularly in pediatric populations. We aimed to investigate the dynamic changes of the etiologies of hospital admissions for common pathogen-associated LRTIs over 8 years, and the results indicate that, in the pre-pandemic era, the most common causes of LRTIs were Mycoplasma pneumoniae (MP) (34.98%), respiratory syncytial virus (RSV), (20.62%) and parainfluenza virus (PIV) (8.16%). Adenovirus (ADV) has surged in the post-pandemic era, surpassing PIV to become one of the leading causes of hospitalized LRTIs cases in children. In contrast, influenza B virus was not significantly affected by NPIs ( P >0.05). Additionally, we observed a rising age trend in children with LRTIs associated with RSV, PIV, ADV, and Influenza A virus (IAV). Furthermore, a model by seasonal autoregressive integrated moving average (SARIMA) time series suggested that the lifting of NPIs led to a rapid rebound of respiratory pathogens, with a gradual return to seasonal trends. Dynamic trends of common pathogens associated pediatric lower respiratory tract infections in Beijing: 2017 to 2025 Li Yanan 1,2,3*, Kang Xuekai 1,2,3*, Deng Zhuo 4*, Xu Xin 4, Xi Yue 4, Sun Hongguo 4, Xie Zhengde 2,3,5 ，Ning Xue 1,2,3, Zhao Chengsong 1,2,3#, Liu Gang 1,2,3# Yanan Li, Xuekai Kang and Zhuo Deng are co-first authors and contributed equally to this work. 1.Department of Infectious Diseases, Beijing Children′s Hospital, Capital Medical University, Beijing 100045, China 2. National Center for Children′s Health, Key Laboratory of Major Diseases in Children, Ministry of Education, Beijing 100045, China 3. Research Unit of Critical infection in Children, Chinese Academy of Medical Sciences，2019RU016, Beijing 100045, China 4. Information Technology Center, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing 100045, China 5. Beijing Key Laboratory of Pediatric Respiratory Infection diseases, National Clinical Research Center for Respiratory Diseases, Laboratory of Infection and Virology, Beijing Pediatric Research Institute, Beijing Children’s Hospital, Capital Medical University, Beijing 100045, China Lower respiratory tract infections (LRTIs) are one of the leading causes of hospitalization in children, with their associated respiratory pathogens typically following seasonal epidemic patterns. However, the COVID-19 pandemic has profoundly altered the landscape of pediatric respiratory infections, causing unprecedented shifts in the epidemiology of common respiratory pathogens. To date, long-term epidemiological surveillance remains limited, particularly in pediatric populations. We aimed to investigate the dynamic changes of the etiologies of hospital admissions for common pathogen-associated LRTIs over 8 years, and the results indicate that, in the pre-pandemic era, the most common causes of LRTIs were Mycoplasma pneumoniae (MP) (34.98%), respiratory syncytial virus (RSV), (20.62%) and parainfluenza virus (PIV) (8.16%). Adenovirus (ADV) has surged in the post-pandemic era, surpassing PIV to become one of the leading causes of hospitalized LRTIs cases in children. In contrast, influenza B virus was not significantly affected by NPIs ( P >0.05). Additionally, we observed a rising age trend in children with LRTIs associated with RSV, PIV, ADV, and Influenza A virus (IAV). Furthermore, a model by seasonal autoregressive integrated moving average (SARIMA) time series suggested that the lifting of NPIs led to a rapid rebound of respiratory pathogens, with a gradual return to seasonal trends. Key words: Etiology; Epidemiological trends; Seasonal dynamics; Lower respiratory tract infections; Pediatric patients 1 Introduction LRTIs are a leading cause of morbidity and mortality in children. The Global Burden of Disease Study estimated that 344 million incident cases and 7.57 million prevalent cases of LRTIs contributed to 2.18 million deaths and 85.5 million DALYs worldwide in 2021, resulting in a major health care consumption [1]. Research suggests that SARS-CoV-2 infection can induce long-term alterations in the innate immune system, and related NPIs significantly disrupt the circulation patterns of seasonal respiratory viruses [2,3]. China officially lifted NPIs on December 7, 2022 [4]. However, the long-term trends of sustained circulation of common respiratory pathogens in pediatric LRTIs cases remain unclear in the second year following the lifting of NPIs. Furthermore, comprehensive studies on the etiological spectrum of pediatric LRTIs are still limited. To visualize the phenomenon, we summarized the epidemiological trends and seasonal dynamics of six common respiratory pathogens in pediatric patients hospitalized with LRTIs at Beijing Children’s Hospital from January 2017 to February 2025. 2 Methods 2.1 Case identification The International Classification of Diseases version 10 (ICD-10) codes were used to identify hospital admissions for any LRTIs of a tertiary children’s hospital between January 2017, and February 2025 (Table S1). All pathogens were detected using polymerase chain reaction [5]. Children admitted to the hospital with LRTIs who tested positive for one of six respiratory pathogens were classified as having virus-associated LRTIs, given the strong causal association between these viruses and LRTIs in hospitalized pediatric patients [5]. 2.2 Data source and variable classification Data were extracted from the Beijing Children’s Hospital Discharge Database, including monthly testing and positive case numbers for six common respiratory pathogens. Cases with documented infections of MP, PIV, ADV, RSV, IAV, and influenza B virus (IBV) from the database were included in this study, which are key causative agents of LRTIs in children [6]. To systematically describe the surveillance data, we accessed differences in etiological distribution among pediatric LRTIs patients by two groups: 1) age groups; 2) the year of implementation and lifting of NPIs. Five age groups were defined based on developmental stages: 1) to <10 years; and 5) ≥10 years. The study period was divided into three phases according to the implementation and lifting of NPIs [7]: 1) the pre-pandemic (2017-2019); 2) the pandemic (2020-2022), and 3) the post-pandemic periods (2023-2025). 2.3 Statistical analysis For comparisons between different periods, Chi-squared test was used for categorical data. Given the well-established cyclical patterns of respiratory pathogen infections, we developed a time series model using seasonal autoregressive integrated moving average (SARIMA) to capture seasonal variations. [6]. The model was trained with data from January 2017 to December 2019 to forecast the monthly detection rates of various respiratory pathogens from January 2020 to February 2025. All seasonal shifts, comparing Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC). Smaller AIC and BIC indicate the better fitting model. Statistical analyses were performed in SPSS (version 26.0) and R (version 4.1) with the packages forecast (8.23.0), tseries (0.10), lubridate (1.9.4) and zoo (1.8-13). 3 Results 3.1 Dynamic trends in the detection rates of LRTIs associated with different respiratory pathogens Figure 1 describes the dynamic trends in cases and detection rates of respiratory pathogens-associated hospitalized pediatric LRTIs patients over 8 years. In the pre-pandemic era, the predominant respiratory pathogens detected in hospitalized children with LRTIs were MP (34.98%), RSV (20.62%), and PIV (8.16%). Following the implementation of NPIs in 2020, LRTIs cases associated with all respiratory pathogens declined significantly, with the most significant reductions observed for ADV (-85.10%) and IAV (-83.33%) ( P <0.001). Interestingly, the detection rate of RSV increased in 2020-2021 compared to the pre-pandemic period. We aimed to compare the post-pandemic period with the pre-pandemic period, highlighting key differences. During the post-pandemic period, cases of MP, ADV, and IAV-associated LRTIs showed a resurgence compared to the pandemic period ( P >0.05; Table 1). Notably, there was a shift in the pattern of respiratory pathogens responsible for LRTIs (Figure 1). The number of hospitalized children with ADV-associated LRTIs increased dramatically compared to the pandemic period, surpassing PIV to become one of the most prevalent pathogens (Table 1). Interestingly, RSV and PIV exhibited an overall decline in detection rates during the post-pandemic period ( P <0.001; Table 1). The detection rate of IBV-associated LRTIs cases was unaffected by NPIs. Fig. 1 Annual patterns of detected respiratory pathogens among hospitalized pediatric patients with LRTI from 2017 to 2024. A) Detection rates; B) Case numbers. 3.2 Dynamic trends in the age distribution of LRTIs associated with different respiratory pathogens Furthermore, we investigated the dynamic changes in age distribution and found that, the age composition of LRTIs associated with other respiratory pathogens showed an upward trend in the post-pandemic period except MP (Figure 1). MP was mainly detected in children aged ≥6 years (64.18%, 1645/2563), a trend that persisted in the post-pandemic period ( P >0.05; Table 1). Importantly, the detection rate among children aged 1 to <3 years significantly increased post-pandemic (15.82% vs. 20.96%, P <0.001; Figure 2A). RSV- and PIV-associated LRTIs were predominantly observed in hospitalized children aged <1 year both before and after the pandemic. However, their proportions significantly declined post-pandemic ( P <0.001; Figure 2B and 2C). Notably, the age groups showing an increase in cases differed between the two pathogens, with RSV mainly rising in children aged 3 to <6 years (4.97% [117/2353] vs. 18.64% [231/1239], P <0.001) and PIV in those aged 6 to <10 years (3.87% [36/931] vs. 17.98% [146/812]; P <0.001). ADV-associated LRTIs were most frequently observed in children aged 1 to age group showed a slight increase in the post-pandemic period, the change was not statistically significant (7.32% vs. 7.65%, P >0.05). In contrast, detection rates rose significantly in all other age groups, especially in children aged ≥10 years ( P <0.001; Figure 2B). For IAV-associated LRTIs, there was a significant increase post-pandemic, particularly among children aged ≥6 years (14.43% [58/402] vs. 45.00% [261/580]; P <0.001; Figure 2E). Conversely, in its most affected age group (<1 years) (33.58%, 135/402), the detection rate significantly declined (31.34% [126/402] vs. 17.43% [106/608]). Similarly, the age distribution of IBV-associated LRTIs shifted over time. Before the pandemic, cases were most observed in children <1 year (25.20% [32/127]) and 3 to <6 years (25.20% [32/127]). However, in the post-pandemic period, the highest proportion of cases was found in children aged 6 to <10 years (27.32% [50/183]). Fig. 2 The changes in age group composition of common respiratory pathogens among hospitalized pediatric patients with LRTIs from 2017 to 2024 Table 1. The change of all respiratory pathogen-associated pediatric LRTIs cases and detection rate during the different periods and different age groups | Baseline 1 | Baseline 2 | ||||||||| | (n/N, %) | (n/N, %) | (n/N, %) | (%) | (n/N, %) | (%) | (%) | |||| | MP | 10039/29,748 | 2563/7328 | 1062/5425 | -58.56 | <0.001 | 6414/16995 | 150.25 | 503.95 | 0.01 | <0.001 | | (33.75) | (34.98) | (19.58) | (37.74) | ||||||| | <1 | 347/4776 | 94/1132 | 43/1036 | -54.26 | <0.001 | 210/2608 | 123.40 | 388.37 | 0.80 | <0.001 | | (7.27) | (8.30) | (4.15) | (8.05) | ||||||| | 1 to <3 | 738/4492 | 213/1346 | 80/1023 | -62.44 | <0.001 | 445/2123 | 108.92 | 456.25 | <0.001 | <0.001 | | (16.43) | (15.82) | (7.82) | (20.96) | ||||||| | 3 to <6 | 2176/7039 | 611/1860 | 245/1424 | -59.90 | <0.001 | 1320/3755 | 116.04 | 438.78 | 0.09 | <0.001 | | (30.91) | (32.85) | (17.21) | (35.15) | ||||||| | 6 to <10 | 4739/8771 | 1196/2088 | 502/1226 | -58.03 | <0.001 | 3041/5457 | 154.26 | 505.78 | 0.23 | <0.001 | | (54.03) | (57.28) | (40.95) | (55.73) | ||||||| | ≥10 | 2039/4670 | 449/902 | 192/716 | -57.24 | <0.001 | 1398/3052 | 211.36 | 628.13 | 0.04 | <0.001 | | (43.66) | (49.78) | (26.82) | (45.81) | ||||||| | RSV | 4623/32859 | 2353/11412 | 1031/5889 | -56.95 | <0.001 | 1239/15558 | -47.34 | 22.31 | <0.001 | <0.001 | | (14.07) | (20.62) | (17.51) | (7.96) | ||||||| | <1 | 3164/10069 | 1874/5261 | 703/2226 | -62.49 | <0.001 | 587/2582 | -68.68 | -16.50 | <0.001 | <0.001 | | (31.42) | (35.62) | (31.58) | (22.73) | ||||||| | 1 to <3 | 736/4862 | 299/1762 | 180/1078 | -39.80 | 0.88 | 257/2022 | -14.05 | 42.78 | <0.001 | 0.003 | | (15.14) | (16.97) | (16.70) | (12.71) | ||||||| | 3 to <6 | 444/6125 | 117/1542 | 96/1129 | -17.95 | 0.39 | 231/3454 | 97.44 | 140.63 | 0.25 | 0.05 | | (7.25) | (7.59) | (8.50) | (6.69) | ||||||| | 6 to <10 | 166/7593 | 34/1943 | 27/883 | -20.59 | 0.04 | 105/4767 | 208.82 | 288.89 | 0.26 | 0.14 | | (2.19) | (1.73) | (3.06) | (2.20) | ||||||| | ≥10 | 113/4210 | 29/904 | 25/573 | -13.79 | 0.26 | 59/2733 | 103.45 | 136.00 | 0.08 | 0.01 | | (2.68) | (3.21) | (4.36) | (2.16) | ||||||| | PIV | 2151/32863 | 931/11416 | 408/5889 | -56.18 | <0.001 | 812/15558 | -12.78 | 336.56 | <0.001 | <0.001 | | (6.55) | (8.16) | (6.93) | (5.22) | ||||||| | <1 | 974/10071 | 558/5263 | 162/2226 | -70.97 | <0.001 | 254/2582 | -54.48 | -56.79 | 0.31 | 0.002 | | (9.67) | (10.60) | (7.28) | (9.84) | ||||||| | 1 to <3 | 539/4862 | 240/1762 | 121/1078 | -49.58 | 0.06 | 178/2022 | -25.83 | 47.11 | <0.001 | 0.04 | | (11.09) | (13.62) | (11.22) | (8.80) | ||||||| | 3 to <6 | 295/6126 | 75/1543 | 66/1129 | -12.00 | 0.29 | 154/3454 | 105.33 | 133.33 | 0.56 | 0.07 | | (4.82) | (4.86) | (5.85) | (4.46) | ||||||| | 6 to <10 | 215/7593 | 36/1943 | 33/883 | -8.33 | 0.01 | 146/4767 | 305.56 | 342.42 | 0.01 | 0.30 | | (2.83) | (1.85) | (3.74) | (3.06) | ||||||| | ≥10 | 128/4211 | 22/905 | 26/573 | 18.18 | 0.03 | 80/2733 | 263.64 | 207.69 | 0.49 | 0.05 | | (3.04) | (2.43) | (4.54) | (2.93) | ||||||| | ADV | 1374/34003 | 396/12227 | 59/6194 | -85.10 | <0.001 | 919/15582 | 132.07 | 1457.63 | <0.001 | <0.001 | | (4.04) | (3.24) | (0.95) | (5.90) | ||||||| | <1 | 179/10228 | 96/5381 | 9/2261 | -90.63 | <0.001 | 74/2586 | -22.92 | 722.22 | 0.003 | <0.001 | | (1.75) | (1.78) | (0.40) | (2.86) | ||||||| | 1 to <3 | 314/5174 | 146/1994 | 13/1154 | -90.10 | <0.001 | 155/2026 | 6.16 | 1092.31 | 0.72 | <0.001 | | (6.07) | (7.32) | (1.13) | (7.65) | ||||||| | 3 to <6 | 357/6453 | 82/1778 | 23/1218 | -71.95 | <0.001 | 252/3457 | 207.32 | 995.65 | <0.001 | <0.001 | | (5.53) | (4.61) | (1.89) | (7.29) | ||||||| | 6 to <10 | 385/7858 | 59/2116 | 11/963 | -81.36 | 0.004 | 315/4779 | 433.90 | 2763.64 | <0.001 | <0.001 | | (4.90) | (2.79) | (1.14) | (6.59) | ||||||| | ≥10 | 139/4290 | 13/958 | 3/598 | -76.92 | 0.13 | 123/2734 | 846.15 | 4000.00 | <0.001 | <0.001 | | (3.24) | (1.36) | (0.50) | (4.50) | ||||||| | IAV | 1049/34912 | 402/12563 | 67/6693 | -83.33 | <0.001 | 580/15656 | 0.44 | 0.08 | 0.03 | <0.001 | | (3.00) | (3.20) | (1.00) | (3.70) | ||||||| | <1 | 223/10410 | 135/5456 | 16/2353 | -88.15 | <0.001 | 72/2601 | -46.67 | 350.00 | 0.45 | <0.001 | | (2.14) | (2.47) | (0.68) | (2.77) | ||||||| | 1 to <3 | 242/5376 | 126/2078 | 16/1263 | -87.30 | <0.001 | 100/2035 | -20.63 | 525.00 | <0.001 | <0.001 | | (4.5) | (6.06) | (1.27) | (4.91) | ||||||| | 3 to <6 | 246/6674 | 83/1859 | 16/1337 | -80.72 | <0.001 | 147/3478 | 77.11 | 818.75 | 0.67 | <0.001 | | (3.69) | (4.46) | (1.20) | (4.23) | ||||||| | 6 to <10 | 214/8002 | 45/2152 | 11/1065 | -75.56 | 0.03 | 158/4785 | 251.11 | 1336.36 | 0.01 | <0.001 | | (2.67) | (2.09) | (1.03) | (3.30) | ||||||| | ≥10 | 124/4450 | 13/1018 | 8/675 | -38.46 | 1.00 | 103/2757 | 692.31 | 1187.50 | <0.001 | <0.001 | | (2.79) | (1.28) | (1.19) | (3.74) | ||||||| | IBV | 399/34601 | 127/12258 | 89/6695 | -29.92 | 0.07 | 183/15648 | 0.44 | 2.06 | 0.30 | 0.32 | | (1.15) | (1.04) | (1.33) | (1.17) | ||||||| | <1 | 71/10374 | 32/5421 | 13/2354 | -59.38 | 1.00 | 26/2599 | -18.75 | 100.00 | 0.05 | 0.08 | | (0.68) | (0.59) | (0.55) | (1.00) | ||||||| | 1 to <3 | 76/5285 | 27/1987 | 20/1264 | -25.93 | 0.65 | 29/2034 | 7.41 | 45.00 | 0.89 | 0.77 | | (1.44) | (1.36) | (1.58) | (1.43) | ||||||| | 3 to <6 | 105/6576 | 32/1764 | 29/1337 | -9.38 | 0.52 | 44/3475 | 37.50 | 51.72 | 0.14 | 0.03 | | (1.60) | (1.81) | (2.17) | (1.27) | ||||||| | 6 to <10 | 93/7948 | 20/2099 | 23/1065 | 15.00 | 0.01 | 50/4784 | 150.00 | 117.39 | 0.80 | 0.01 | | (1.17) | (0.95) | (2.16) | (1.05) | ||||||| | ≥10 | 54/4418 | 16/987 | 4/675 | -75.00 | 0.07 | 34/2756 | 112.50 | 750.00 | 0.42 | 0.42 | | (1.22) | (1.62) | (0.59) | (1.23) | Abbreviations: LRTIs: Lower respiratory tract infections; MP: Mycoplasma pneumoniae; RSV: respiratory syncytial virus; PIV: parainfluenza virus; ADV: adenovirus; IAV: influenza A virus, IBV: influenza B virus. * n: the number of LRTIs cases related to different respiratory pathogens in different periods; N: the number of cases tested; The brackets refer to the detection rates. ** The table highlighted in pink indicates that the differences of detection rates are statistically significant. Change a : The change proportion of all respiratory pathogen-associated LRTIs cases of baseline 2 compared with baseline 1. Calculated as: (Cases2020-2022 – Cases2017-2019)/Cases2017-2019 × 100% Change b : The change proportion of all respiratory pathogen-associated LRTIs cases of 2023-2024 compared with baseline 1. Calculated as: (Cases2023-2024 – Cases2017-2019)/Cases2017-2019 × 100% Change c : The change proportion of all respiratory pathogen-associated LRTIs cases of 2023-2024 compared with baseline 2. Calculated as: (Cases2023-2024 – Cases2020-2022)/Cases2020-2022 × 100% P value : Differences in detection rates of different pathogens and age groups. a: The pre-pandemic period (2017-2019) and the pandemic period (2020-2022); b: The pre-pandemic period (2017-2019) and the post-pandemic period (2023-2024); c: The pandemic period (2020-2022) and post-pandemic period (2023-2024). 3.3 Dynamic trend in the monthly detection rates of LRTIs associated with different respiratory pathogens Additionally, we analyzed the seasonality of six respiratory pathogens associated with LRTIs in pediatric patients hospitalized from January 2017 to February 2025, indicating atypical trends (Figure 3). In the pre-pandemic period, the seasonality of MP-associated LRTIs is predominantly from July to December, peaking around September. Although the peak was lower, MP regained its seasonal cycle in 2021. By 2023, an atypical trend emerged, with an unprecedented peak in October and sustained high infection rates. However, the infection peak demonstrated a trend toward returning to pre-pandemic levels by September 2024 compared to the predicted line. Unlike other pathogens, the seasonality of RSV and PIV-associated LRTIs was less affected by NPIs. RSV-associated LRTIs peaked around January in the pre-pandemic era, and remained unchanged during the pandemic. However, in 2023, the peak shifted to May and returned to its usual seasonal trends in December. PIV maintained its annual epidemic peak, primarily between April and September. The seasonality of ADV, IAV, and IBV subsided during the COVID-19 pandemic (Figure 3). The seasonality of ADV-associated LRTIs peaked between June and September in the pre-pandemic period. However, starting in August 2023, a gradual recovery in seasonality was observed, with a significant peak reached in December. Subsequently, the seasonality returned to trends in May 2024 comparable to the pre-pandemic period. The seasonality of IAV was most significantly affected by NPIs. Its seasonal epidemic is usually from December to March, reaching its peak in January. In 2023, the seasonal peak of IAV was delayed to March, with its previous seasonal pattern resuming in December of the same year. In contrast to IAV, IBV showed a distinct seasonality. Before the pandemic, IBV-associated LRTIs typically peaked between January and March. Nevertheless, IBV quickly regained its seasonal cycle starting in 2021. Fig. 3 Observed and model-fitted time series of monthly detection rates between January 2017 and February 2025. The red line represents the predicted value by fitting the model from January 2017 to December 2019; the red dotted line represents that hypothetical detection rate during January 2020- February 2025 in the absence of NPIs was projected using the SARIMA model based on January 2017-December 2019; Transparent area: Pre-pandemic period (2017–2019); Gray area: COVID-19 pandemic period (2020–2022); Yellow area: Post-pandemic period (2023–2025). Abbreviations: NPIs, non-pharmacological interventions; SARIMA, seasonal autoregressive integrated moving average. 4 Discussion This study provides a more comprehensive insight into the etiology and dynamic epidemic trends of LRTIs over an 8-year in hospitalized children at a large pediatric hospital. Additionally, we highlight the dynamic changes across different age groups, which can help monitor and track LRTIs cases to assist in disease control and prevention. Our study indicated that MP has played a critical role in pediatric LRTIs over the past eight years. It typically follows a 3-7 year epidemic cycle [8]. A significant surge in MP cases was reported globally in 2023, identified as a distinct epidemic among children [9,10]. Urbieta proposed that this follows the natural epidemiological cycle observed after the 2018 outbreak [9]. Previous studies have shown that MP epidemic cycles typically span 6 to 18 months, a pattern consistent with our long-term surveillance data [11]. RSV also plays a significant role in pediatric LRTIs. Notably, its detection rate exhibited a distinct surge during the early phase of NPI implementation, a trend also observed in Foley’s study, which was explained as an expanded pool of RSV-naïve individuals [12]. Its post-pandemic circulation patterns warrant further attention. Although several studies report a surge in RSV cases in 2023, our observations in pediatric LRTIs cases suggest that despite a slight increase in detection rates that year, RSV has shown an overall decline compared to the pre-pandemic period [13]. However, it’s uncertain whether this represents a temporary change or a more sustained trend. Advancements in molecular biology techniques have contributed to a deeper understanding of the role of respiratory pathogens in LRTIs. Compared to the pre-pandemic period, the incidence of LRTIs cases attributed to respiratory pathogens other than RSV and PIV has increased in the post-pandemic era, which may be largely influenced by changes in testing practices and the public’s acceptance of nucleic acid testing methods [14]. The increasing age trend observed in LRTIs cases associated with RSV, PIV, ADV, and IAV may also be attributed to these factors. However, relevant studies on this topic remain limited. Moreover, the hypothesis of ’immunological debt’ has also been proposed to explain shifts in respiratory pathogen dynamics since the COVID-19 outbreak, garnering widespread attention [15]. It is worth noting that whether and when children will fully compensate for this immunological debt remains a subject of ongoing investigation. Our continued surveillance through February 2025 provides new insights into this issue, indicating that most common respiratory pathogens have gradually returned to their typical seasonal trends. There is a limitation in our study. The potential differences in the proportion of children tested for LRTIs across different periods, which could be influenced by changes in healthcare-seeking behaviors. However, as the National Children’s Medical Center of China, all patients have undergone systematic testing for specific pathogens over the years, with standardized testing conducted according to clinical diagnostic protocols. Therefore, the detection rate can be applied without bias to those children who were not tested during the corresponding periods, ensuring that our results are representative. In conclusion, our study provides valuable insights into the evolving epidemiological patterns of respiratory pathogens in pediatric LRTIs. The observed trends in pathogen circulation underscores the importance of continued health care vigilance and preparedness. Funding Source All phases of this study were supported by Beijing Research Center for Respiratory Infectious Diseases Project (BJRID2025-008), 2022 Beijing Major Epidemic Prevention and Control Specially Construction Project (2-1-2-6-15) and Training Plan for High level Public Health Technical Talents Construction Project (123567).

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Authors Metrics & Citations Metrics Article Usage 252views 172downloads Citations Download citation Li Yanan, Kang Xuekai, Deng Zhuo, et al. Dynamic trends of common pathogens associated pediatric lower respiratory tract infections in Beijing: 2017 to 2025. Authorea. 25 March 2025. DOI: https://doi.org/10.22541/au.174287900.06091265/v1 DOI: https://doi.org/10.22541/au.174287900.06091265/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu.