Burden of asymptomatic malaria in Sub-Saharan migrants attending an outpatient clinic in Rome from February 2024 to January 2025.

Burden of asymptomatic malaria in Sub-Saharan migrants attending an outpatient clinic in Rome from February 2024 to January 2025. | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Burden of asymptomatic malaria in Sub-Saharan migrants attending an outpatient clinic in Rome from February 2024 to January 2025. Francesca Faraglia, Serena Vita, Dimitra Kontogiannis, Tommaso Ascoli Bartoli, and 9 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6863865/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 23 Oct, 2025 Read the published version in Infectious Diseases of Poverty → Version 1 posted 5 You are reading this latest preprint version Abstract Background Sub-Saharan African (SSA) migrants may harbor asymptomatic Plasmodium infections long after leaving endemic regions, representing a potential public health concern in host countries. However, data on the prevalence and persistence of such infections post-migration are limited. Methods Between February 2024 and January 2025, SSA migrants attending the Lazzaro Spallanzani Institute’s mobile population clinic were screened for malaria using rapid diagnostic tests (RDTs), thick blood smears, and PCR. Eligibility criteria included age ≥ 16, absence of fever, and origin or transit through malaria-endemic regions. Additional screenings for tuberculosis, schistosomiasis, and viral hepatitis were also conducted. Results Among 87 asymptomatic migrants tested, PCR detected Plasmodium spp. in 5 cases (6.02%), while RDT identified 2 (2.29%). Identified species included P. falciparum , P. malariae , P. ovale , and one mixed infection. The longest time since arrival among positive cases was 181 days; including detention in Libya, the median duration since departure from endemic areas was over 600 days. Conclusions Asymptomatic malaria persists months after arrival and is underdetected by RDTs. PCR enhances diagnostic sensitivity, supporting its use in screening migrants from endemic areas. These findings highlight the need for inclusive, long-term infectious disease screening policies tailored to mobile populations. Asymptomatic malaria Plasmodium infection Malaria screening Migrant health screening Infectious disease surveillance Figures Figure 1 Background Malaria remains a global health challenge, especially in Sub-Saharan Africa (SSA), which accounted for 94% of the 249 million cases and 608,000 deaths worldwide in 2022 1 . Repeated exposure leads to partial immunity, with many harbouring asymptomatic infections that sustain transmission and hinder elimination efforts 2 . Asymptomatic migrants from malaria-endemic regions may carry these infections in non-endemic countries, with prevalence rates ranging from 3–30% 3,4 . Despite the risks, routine screening in Europe is not widely implemented, unlike in countries such as Australia and the U.S. 5 , 6 . A Swedish study found a 9% overall prevalence rate using a screening policy based on molecular assay, detecting higher rates among Ugandan migrant adults and children 7 . This highlights the importance of carefully screening individuals arriving from areas with high rates of endemic diseases. The study aimed to evaluate the prevalence of malaria parasites in asymptomatic migrants from SSA who attended the outpatient clinic for mobile populations at the Lazzaro Spallanzani National Institute for Infectious Diseases. Methods Study design and study population Since February 2024, an outpatient clinic at the Lazzaro Spallanzani National Institute for Infectious Diseases is dedicated to serve migrants, especially the mobile population residing in urban and suburban areas of Rome. The clinic is conducting an infectious disease screening program (February 2024–January 2025), including tests for Schistosoma , Hepatitis B and C Virus (HBV and HCV), and HIV testing, and Interferon Gamma Release Assay (IGRA) test. Malaria screening with rapid diagnostic test (RDT), thick blood smear, and polymerase chain reaction (PCR) assay was offered to asymptomatic patients from endemic regions in SSA or those with migration routes through these areas, regardless of their duration of residence in Italy. Participants gave informed consent, with translators' assistance when necessary. Exclusion criteria included origin from non-endemic regions, age under 16, and fever at the time of testing. Patients with positive results were referred to the in-patient clinic for evaluation and antimalarial drug therapy. During the clinical visit we collected data about the origin country, date of departure, migration route, duration of migration, method of travel to reach Italy, time spent in detention centres if the case, arrival date in Italy, co-morbidities and medications, previous malaria infections, specific treatments, as well as any persistent symptoms at the time of evaluation. Detection of malaria parasites RDTs (CareUs Malaria Rapydtest® Combo Pf/PAN) were performed on sampling day to detect P. falciparum , P. vivax , P. malariae , or P. ovale . If positive for non- P. falciparum species, an additional rapid test (Screen Test Malaria P.F./P.V. rapid test; Screen Italia, Perugia, Italy) was conducted to differentiate P. vivax , . For RDT-negative samples, DNA extraction was performed on the blood cell fraction using Alethia® Malaria (Meridian Diagnostics, Cincinnati, OH, US) for rapid detection of Plasmodium spp. RDT-positive or rapid PCR-positive samples underwent PCR (Malaria Differentiation REAL TIME PCR Detection Kit - Certest Biotec®, Zaragoza, Spain), identifying P. falciparum , P. vivax , P. ovale , P. knowlesi , and P. malariae . Results A total of 94 participants from SSA countries were included in the study. Five declined participation and were excluded. Of the remaining 89, two had invalid test results and could not be followed up as they had left the city. Among the 87 migrants tested, all underwent RDT, thick blood smear, and PCR for Plasmodium spp (Fig. 1 a). The most represented countries were Mali (17, 18.09%) and Sudan (13, 13.83%). Males accounted for 82 participants (87.2%), with a median age of 25 years (Fig. 1 b). The median time from arrival in Italy to the first screening visit was 143 days (IQR115-154) (Supplemental materials 1). PCR detected Plasmodium spp. in 5 of 83 patients (6.02%), while RDTs were positive in 2 of 87 cases (2.29%) (Supplemental materials 1), and all RDT-positive samples were PCR-confirmed. PCR identified one case of P. falciparum , one mixed P. falciparum /malariae, one P. ovale , and two P. malariae . The mixed infection was the only case confirmed by thick blood smear (Table 1 ). RDT demonstrated a sensitivity of 40% (95% CI 5.27–85.34) and a specificity of 100% (95% CI 95.55–100) in asymptomatic patients. Table 1 Characteristics of patients with asymptomatic malaria. Pt Sex Age Nationality Days from arrival Days from arrival in Libia to visit RDT Thick blood smear PCR malaria Therapy Schisto Ab IGRA test HBsAg/ HBsAb/HBcAb 1 M 30 Benin 181 NA pos neg P. falciparum DHA/PPQ pos pos -/-/+ 2 M 37 Sudan 7 589 neg neg P. malariae HCQ pos pos -/-/+ 3 M 29 Mali 115 660 neg neg P. malariae DHA/PPQ pos neg -/-/+ 4 M 41 Ivory Coast 143 184 neg neg P. ovale DHA/PPQ primaquine neg pos -/-/+ 5 M 22 Mali 141 1784 pos pos (67 trophozoites/mmc 0,001%) P. falciparum P. malariae DHA/PPQ neg neg -/+/- Median value (IQR) 30 (29–37) 141 (115–143) 624 (488–941) RDT: malaria rapid diagnostic test; PCR: Polymerase chain reaction; NA: not available; DHA/PPQ: piperaquine/dihydroartemisinin; HCQ: hydroxychloroquine The characteristics of the five patients are illustrated in Table 1 . They were all male subjects with a 30 years-old median age. Four of them had travelled through Libya, where they remained detained for extended periods, with a median duration of 624 days. The median time of arrival in Italy was 141 days, similar to the median time of the whole population (143 days). The longest residence in Italy (181 days) was reported in the P. falciparum case, while the shortest (7 days) was in a P. malariae infection. Including the time spent in Libya, a malaria-free country since 2015, the median duration since leaving malaria-endemic regions was 624.5 days. No laboratory abnormalities were found in the complete blood count, with all haemoglobin levels within the normal range (data not shown). Screening for other infectious diseases revealed that three subjects were positive for interferon-gamma release assay (IGRA) with no evidence at chest X-rays and smear tests of active tuberculosis. Three individuals showed positive serology for Schistosoma species and received antiparasitic treatment. Four had evidence of prior HBV infection (HBsAg-negative, HBcAb IgG-positive, anti-HBs-negative), while one had been vaccinated against HBV. HIV and HCV serology results were negative for all participants. All five subjects were referred to the Clinical Department of the Spallanzani Institute for antimalarial treatment. Discussion A 6% prevalence rate of malaria infection was observed among asymptomatic male migrants from SSA countriesThe longest residence in Italy among positive cases was 181 days with a median parasite survival of approximately five months, but extended to 18 months when including detention periods in Libya. Asymptomatic co-infections with schistomiasis and latent tuberculosis, and previous HBV exposure is reported, reflecting the endemic nature of these infections in their origin countries 8 – 11 . The persistence of Plasmodium infection in humans is not well-documented, with studies reporting durations from 6 to 386 days for blood-stage infections of P. falciparum 7 , 12 . Asymptomatic carriers, despite lacking typical symptoms like fever, act as reservoirs and can facilitate parasite transmission in non-endemic regions with suitable vectors, posing significant challenges to malaria control efforts. The recent re-emergence of Anopheles sacharovi in Apulia, thought to be extinct in Italy for over 50 years, highlights the growing receptivity of Italian southern regions and underscores its public health implications 13 . With approximately 8,000 imported cases of malaria reported annually in Europe, the potential for Plasmodium transmission by gametocyte carriers arriving from endemic regions remains a significant public health concern 1 , 14 , 15 . Screening strategies for malaria vary considerably across countries. In Italy, guidelines implemented in July 2015 recommend the use of RDTs for symptomatic migrants, while PCR testing is reserved for high-risk groups, including pregnant women and immunocompromised individuals 16 . These variations in screening practices reflect differences in national and international asylum policies. Compared to microscopy and RDTs, PCR testing demonstrates superior sensitivity, particularly for detecting low-level parasitaemia in asymptomatic individuals, highlighting its utility as a screening modality for migrants originating from malaria-endemic areas 3 , 7 . Italy received approximately 225,000 refugees and migrants by sea between 2023 and 2024 17 , primarily from Burkina Faso, Guinea, Cameroon, Ivory Coast, and Nigeria 18 . In 2023, the country’s foreign resident population was 5.1 million, 19 with approximately 500,000 undocumented migrants. 20 These findings underscore the importance of implementing inclusive screening programs based on epidemiological data from both the country of origin and the migration route. The involvement of frontline healthcare workers and general practitioners is essential to effectively address the healthcare access barriers faced by asylum seekers, undocumented migrants, and, more broadly, mobile populations. Conclusions This study confirms that asymptomatic Plasmodium infections may persist for several months after arrival in a non-endemic country, underscoring the long-term resilience of the parasite in the absence of clinical symptoms. The limited sensitivity of rapid diagnostic tests (RDTs), compared to molecular methods such as PCR, resulted in a significant underdetection of cases, raising concerns about the reliability of standard diagnostic approaches in low-transmission settings. The fact that infections were still detectable over six months post-arrival—and more than 600 days since departure from endemic regions when accounting for prolonged transit and detention—indicates that standard screening windows based on recent travel history may fail to identify chronic carriers. Our findings strongly support the integration of PCR-based diagnostic strategies into routine screening protocols for migrants from malaria-endemic areas, particularly within comprehensive health assessments offered upon arrival and during follow-up. This approach would contribute to early detection, reduce the potential for local transmission (especially in receptive areas), and improve individual health outcomes. More broadly, these results point to the urgent need for inclusive and sustained infectious disease screening policies that are not limited to immediate post-entry checks but are tailored to the specific risk profiles and migration trajectories of mobile populations. Strengthening such policies is essential not only for individual case management but also for informed public health planning in increasingly multicultural and mobile societies. Abbreviations • SSA Sub–Saharan Africa • RDT Rapid Diagnostic Test • PCR Polymerase Chain Reaction • HBV Hepatitis B Virus • HCV Hepatitis C Virus • HIV Human Immunodeficiency Virus • IGRA Interferon Gamma Release Assay • HBsAg Hepatitis B Surface Antigen • HBcAb Hepatitis B Core Antibody • IQR Interquartile Range • CI Confidence Interval Declarations Ethics Approval and consent to partecipate The study was approved by Ethical Committee of the Lazio Area 4 (44-2025). Informed consent was obtained from all subjects involved in the study. Consent for publication All patient gave informed consent for collecting personal data for research purposes. Availability of data and materials All data generated or analyzed relating to this study are presented within this published article. Competing interests The authors declare that they have no competing interests. Funding This study was supported by funds allocated to the National Institute for Infectious Diseases “Lazzaro Spallanzani”, IRCCS, 00149, Rome (Italy), from the Italian Ministry of Health (Linea 1 Malattie Infettive tropicali e neglette: aspetti patogenetici, immunologici e diagnostici, 2025-2027). Authors' contributions FF and SV : conception and design of the study, data acquisition, and writing the original draft of the manuscript. DK : writing the original draft of the manuscript, data analysis, and interpretation of results. TAB , SR , NB , GM, AC, ADA : investigation, data acquisition and interpretation. AV and BB: experiment, analysis, interpretation of laboratory data and revision of the manuscript. CF : validation, writing, review and editing. EN : validation, writing, review, editing, supervision and funding acquisition. All authors read and approved the final version of the manuscript and agree to be accountable for all aspects of the work. Acknowledgement Mobile-INMI group: Elena Boschiavo, Patrizia De Marco, Maria Letizia Giancola, Alessandra Lamonaca, Andrea Mariano, Claudia Palazzolo, Sara Pantanella, Giuseppa Tarabù, Maria Virginia Tomassi. References World Malaria Report 2024: Addressing Inequity in the Global Malaria Response. Geneva: World Health Organization; 2024. Licence: CC BY-NC-SA 3.0 IGO. Bousema T, Okell L, Felger I, Drakeley C. Asymptomatic malaria infections: detectability, transmissibility and public health relevance. Nat Rev Microbiol. 2014;12(12):833–40. 10.1038/nrmicro3364 . Matisz CE, Naidu P, Shokoples SE, et al. Post-Arrival Screening for Malaria in Asymptomatic Refugees Using Real-Time PCR. Am J Trop Med Hyg. 2011;84(1):161–5. 10.4269/ajtmh.2011.10-0494 . Marangi M, Di Tullio R, Mens PF, et al. Prevalence of Plasmodium spp. in malaria asymptomatic African migrants assessed by nucleic acid sequence based amplification. Malar J. 2009;8:12. 10.1186/1475-2875-8-12 . Chaves NJ, Paxton GA, Biggs BA, et al. The Australasian Society for Infectious Diseases and Refugee Health Network of Australia recommendations for health assessment for people from refugee-like backgrounds: an abridged outline. Med J Aust. 2017;206(7):310–5. 10.5694/mja16.00826 . CDC, Malaria. Immigrant and Refugee Health. April 15, 2024. Accessed April 2, 2025. https://www.cdc.gov/immigrant-refugee-health/hcp/domestic-guidance/malaria.html Wångdahl A, Bogale RT, Eliasson I, et al. Malaria parasite prevalence in Sub-Saharan African migrants screened in Sweden: a cross-sectional study. Lancet Reg Health Eur. 2023;27:100581. 10.1016/j.lanepe.2022.100581 . Aula OP, McManus DP, Jones MK, Gordon CA. Schistosomiasis with a Focus on Africa. Trop Med Infect Dis. 2021;6(3):109. 10.3390/tropicalmed6030109 . Fasola FA, Fowotade AA, Faneye AO, Adeleke A. Prevalence of hepatitis B virus core antibodies among blood donors in Nigeria: Implications for blood safety. Afr J Lab Med. 2022;11(1). 10.4102/ajlm.v11i1.1434 . Salpini R, Fokam J, Ceccarelli L, et al. High Burden of HBV-Infection and Atypical HBV Strains among HIV-infected Cameroonians. Curr HIV Res. 2016;14(2):165–71. 10.2174/1570162x13666150930114742 . Mbuya AW, Mboya IB, Semvua HH, Mamuya SH, Msuya SE. Prevalence and factors associated with tuberculosis among the mining communities in Mererani, Tanzania. Tsima BM, ed. PLOS ONE. 2023;18(3):e0280396. 10.1371/journal.pone.0280396 Ashley EA, White NJ. The duration of Plasmodium falciparum infections. Malar J. 2014;13:500. 10.1186/1475-2875-13-500 . Raele DA, Severini F, Toma L, et al. Anopheles sacharovi in Italy: first record of the historical malaria vector after over 50 years. Parasit Vectors. 2024;17(1):182. 10.1186/s13071-024-06252-2 . European Centre for Disease Prevention and Control. Malaria. ECDC. Annual Epidemiological Report for 2019. Stockholm: ECDC; 2021. Fact sheet about malaria. Accessed April 2. 2025. https://www.who.int/news-room/fact-sheets/detail/malaria I controlli alla frontiera. La frontiera dei controlli. Accessed April 2. 2025. https://www.iss.it/documents/20126/0/LG_Controlli+frontiera.pdf/7099fb2e-5b37-a57f-5009-434d816945e9?t=1582276359203 Rifugiati e Migranti in Europa. Una donazione per aiutare i bambini. June 14. 2021. Accessed April 2, 2025. https://unicef.it/emergenze/rifugiati-migranti-europa cruscotto_statistico_giornaliero_31_dicembre_2024- ISTAT, Accessed. April 2, 2025. http://www.libertaciviliimmigrazione.dlci.interno.gov.it/sites/default/files/allegati/cruscotto_statistico_giornaliero_31_dicembre_2024.pdf UNHCR-IOM Joint Annual Overview 2023. Fondazione ISMU. Integrazione, Asilo, Lavoro, Salute e Welfare, Religioni, Educazione e Intercultura, Europa, Statistica XXIX Rapporto Sulle Migrazioni 2023. Supplementary Files SupplementalMater1.docx Supplemental materials 1. Characteristics of Sub-Saharan (SSA) patients and patients with asymptomatic malaria. Cite Share Download PDF Status: Published Journal Publication published 23 Oct, 2025 Read the published version in Infectious Diseases of Poverty → Version 1 posted Reviewers agreed at journal 14 Jul, 2025 Reviewers invited by journal 10 Jul, 2025 Editor assigned by journal 10 Jul, 2025 First submitted to journal 09 Jul, 2025 Editorial decision: Major revision 12 Jun, 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-6863865","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":483365177,"identity":"6a828153-3b04-434f-9c37-edf46c945b45","order_by":0,"name":"Francesca Faraglia","email":"","orcid":"","institution":"INMI: Istituto Nazionale Malattie Infettive Lazzaro Spallanzani","correspondingAuthor":false,"prefix":"","firstName":"Francesca","middleName":"","lastName":"Faraglia","suffix":""},{"id":483365178,"identity":"d2942aa9-fc79-44c3-91f1-f386621ea03c","order_by":1,"name":"Serena Vita","email":"","orcid":"","institution":"INMI: Istituto 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Spallanzani","correspondingAuthor":false,"prefix":"","firstName":"Carla","middleName":"","lastName":"Fontana","suffix":""},{"id":483365189,"identity":"23a66996-84ca-4b9b-8214-c5ada37ee9e4","order_by":12,"name":"Emanuele Nicastri","email":"","orcid":"","institution":"INMI: Istituto Nazionale Malattie Infettive Lazzaro Spallanzani","correspondingAuthor":false,"prefix":"","firstName":"Emanuele","middleName":"","lastName":"Nicastri","suffix":""}],"badges":[],"createdAt":"2025-06-10 14:04:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6863865/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6863865/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s40249-025-01379-5","type":"published","date":"2025-10-23T16:16:41+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":86673576,"identity":"02e79fe1-1514-4249-aaa5-5c0c63a5a742","added_by":"auto","created_at":"2025-07-14 11:48:33","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":141642,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Flowchart showing the identification process for individuals with asymptomatic malaria; (b) Nationalites of study population.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6863865/v1/a5522ff27769f6754c47675c.png"},{"id":94490681,"identity":"77384193-48f6-47e6-869b-9a34cb910aba","added_by":"auto","created_at":"2025-10-27 17:13:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":813983,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6863865/v1/9cad991c-ec22-46f8-9096-03cf039f60bb.pdf"},{"id":86672526,"identity":"b2cb86d2-61b8-48f0-9571-6598c2c85c2e","added_by":"auto","created_at":"2025-07-14 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Characteristics of Sub-Saharan (SSA) patients and patients with asymptomatic malaria.\u003c/p\u003e","description":"","filename":"SupplementalMater1.docx","url":"https://assets-eu.researchsquare.com/files/rs-6863865/v1/c2d7285a72a6b6ff9bd909d5.docx"}],"financialInterests":"","formattedTitle":"Burden of asymptomatic malaria in Sub-Saharan migrants attending an outpatient clinic in Rome from February 2024 to January 2025.","fulltext":[{"header":"Background","content":"\u003cp\u003eMalaria remains a global health challenge, especially in Sub-Saharan Africa (SSA), which accounted for 94% of the 249\u0026nbsp;million cases and 608,000 deaths worldwide in 2022\u003csup\u003e1\u003c/sup\u003e. Repeated exposure leads to partial immunity, with many harbouring asymptomatic infections that sustain transmission and hinder elimination efforts\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Asymptomatic migrants from malaria-endemic regions may carry these infections in non-endemic countries, with prevalence rates ranging from 3\u0026ndash;30%\u003csup\u003e3,4\u003c/sup\u003e. Despite the risks, routine screening in Europe is not widely implemented, unlike in countries such as Australia and the U.S.\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. A Swedish study found a 9% overall prevalence rate using a screening policy based on molecular assay, detecting higher rates among Ugandan migrant adults and children\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. This highlights the importance of carefully screening individuals arriving from areas with high rates of endemic diseases.\u003c/p\u003e\u003cp\u003eThe study aimed to evaluate the prevalence of malaria parasites in asymptomatic migrants from SSA who attended the outpatient clinic for mobile populations at the Lazzaro Spallanzani National Institute for Infectious Diseases.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cb\u003eStudy design and study population\u003c/b\u003e\u003c/p\u003e\u003cp\u003eSince February 2024, an outpatient clinic at the Lazzaro Spallanzani National Institute for Infectious Diseases is dedicated to serve migrants, especially the mobile population residing in urban and suburban areas of Rome. The clinic is conducting an infectious disease screening program (February 2024\u0026ndash;January 2025), including tests for \u003cem\u003eSchistosoma\u003c/em\u003e, Hepatitis B and C Virus (HBV and HCV), and HIV testing, and Interferon Gamma Release Assay (IGRA) test. Malaria screening with rapid diagnostic test (RDT), thick blood smear, and polymerase chain reaction (PCR) assay was offered to asymptomatic patients from endemic regions in SSA or those with migration routes through these areas, regardless of their duration of residence in Italy. Participants gave informed consent, with translators' assistance when necessary. Exclusion criteria included origin from non-endemic regions, age under 16, and fever at the time of testing.\u003c/p\u003e\u003cp\u003ePatients with positive results were referred to the in-patient clinic for evaluation and antimalarial drug therapy. During the clinical visit we collected data about the origin country, date of departure, migration route, duration of migration, method of travel to reach Italy, time spent in detention centres if the case, arrival date in Italy, co-morbidities and medications, previous malaria infections, specific treatments, as well as any persistent symptoms at the time of evaluation.\u003c/p\u003e\u003cp\u003e\u003cb\u003eDetection of malaria parasites\u003c/b\u003e\u003c/p\u003e\u003cp\u003eRDTs (CareUs Malaria Rapydtest\u0026reg; Combo Pf/PAN) were performed on sampling day to detect \u003cem\u003eP. falciparum\u003c/em\u003e, \u003cem\u003eP. vivax\u003c/em\u003e, \u003cem\u003eP. malariae\u003c/em\u003e, or \u003cem\u003eP. ovale\u003c/em\u003e. If positive for non-\u003cem\u003eP. falciparum\u003c/em\u003e species, an additional rapid test (Screen Test Malaria P.F./P.V. rapid test; Screen Italia, Perugia, Italy) was conducted to differentiate \u003cem\u003eP. vivax\u003c/em\u003e, .\u003c/p\u003e\u003cp\u003eFor RDT-negative samples, DNA extraction was performed on the blood cell fraction using Alethia\u0026reg; Malaria (Meridian Diagnostics, Cincinnati, OH, US) for rapid detection of \u003cem\u003ePlasmodium\u003c/em\u003e spp. RDT-positive or rapid PCR-positive samples underwent PCR (Malaria Differentiation REAL TIME PCR Detection Kit - Certest Biotec\u0026reg;, Zaragoza, Spain), identifying \u003cem\u003eP. falciparum\u003c/em\u003e, \u003cem\u003eP. vivax\u003c/em\u003e, \u003cem\u003eP. ovale\u003c/em\u003e, \u003cem\u003eP. knowlesi\u003c/em\u003e, and \u003cem\u003eP. malariae\u003c/em\u003e.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 94 participants from SSA countries were included in the study. Five declined participation and were excluded. Of the remaining 89, two had invalid test results and could not be followed up as they had left the city.\u003c/p\u003e\u003cp\u003eAmong the 87 migrants tested, all underwent RDT, thick blood smear, and PCR for \u003cem\u003ePlasmodium\u003c/em\u003e spp (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe most represented countries were Mali (17, 18.09%) and Sudan (13, 13.83%). Males accounted for 82 participants (87.2%), with a median age of 25 years (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The median time from arrival in Italy to the first screening visit was 143 days (IQR115-154) (Supplemental materials 1).\u003c/p\u003e\u003cp\u003ePCR detected \u003cem\u003ePlasmodium\u003c/em\u003e spp. in 5 of 83 patients (6.02%), while RDTs were positive in 2 of 87 cases (2.29%) (Supplemental materials 1), and all RDT-positive samples were PCR-confirmed. PCR identified one case of \u003cem\u003eP. falciparum\u003c/em\u003e, one mixed P. \u003cem\u003efalciparum\u003c/em\u003e/malariae, one \u003cem\u003eP. ovale\u003c/em\u003e, and two \u003cem\u003eP. malariae\u003c/em\u003e. The mixed infection was the only case confirmed by thick blood smear (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). RDT demonstrated a sensitivity of 40% (95% CI 5.27\u0026ndash;85.34) and a specificity of 100% (95% CI 95.55\u0026ndash;100) in asymptomatic patients.\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\u003eCharacteristics of patients with asymptomatic malaria.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"13\"\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=\"char\" char=\".\" 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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePt\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSex\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eAge\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNationality\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eDays from arrival\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eDays from arrival in Libia to visit\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eRDT\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eThick blood smear\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003ePCR malaria\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003eTherapy\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u003cp\u003eSchisto Ab\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c12\"\u003e\u003cp\u003eIGRA test\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c13\"\u003e\u003cp\u003eHBsAg/ HBsAb/HBcAb\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBenin\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e181\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eNA\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003epos\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eneg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eP. falciparum\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003eDHA/PPQ\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003epos\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003epos\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-/-/+\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eSudan\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e589\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eneg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eneg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eP. malariae\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003eHCQ\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003epos\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003epos\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-/-/+\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMali\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e115\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e660\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eneg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eneg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eP. malariae\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003eDHA/PPQ\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003epos\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003eneg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-/-/+\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eIvory Coast\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e143\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e184\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003eneg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003eneg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eP. ovale\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003eDHA/PPQ\u003c/p\u003e\u003cp\u003eprimaquine\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003eneg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003epos\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-/-/+\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMali\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e141\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e1784\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003epos\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u003cp\u003epos (67 trophozoites/mmc 0,001%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eP. falciparum P. malariae\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003eDHA/PPQ\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u003cp\u003eneg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003eneg\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-/+/-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eMedian value (IQR)\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e30\u003c/p\u003e\u003cp\u003e(29\u0026ndash;37)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e141\u003c/p\u003e\u003cp\u003e(115\u0026ndash;143)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e624\u003c/p\u003e\u003cp\u003e(488\u0026ndash;941)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"13\"\u003eRDT: malaria rapid diagnostic test; PCR: Polymerase chain reaction; NA: not available; DHA/PPQ: piperaquine/dihydroartemisinin; HCQ: hydroxychloroquine\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe characteristics of the five patients are illustrated in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. They were all male subjects with a 30 years-old median age. Four of them had travelled through Libya, where they remained detained for extended periods, with a median duration of 624 days. The median time of arrival in Italy was 141 days, similar to the median time of the whole population (143 days). The longest residence in Italy (181 days) was reported in the \u003cem\u003eP. falciparum\u003c/em\u003e case, while the shortest (7 days) was in a \u003cem\u003eP. malariae\u003c/em\u003e infection. Including the time spent in Libya, a malaria-free country since 2015, the median duration since leaving malaria-endemic regions was 624.5 days.\u003c/p\u003e\u003cp\u003eNo laboratory abnormalities were found in the complete blood count, with all haemoglobin levels within the normal range (data not shown). Screening for other infectious diseases revealed that three subjects were positive for interferon-gamma release assay (IGRA) with no evidence at chest X-rays and smear tests of active tuberculosis. Three individuals showed positive serology for \u003cem\u003eSchistosoma\u003c/em\u003e species and received antiparasitic treatment. Four had evidence of prior HBV infection (HBsAg-negative, HBcAb IgG-positive, anti-HBs-negative), while one had been vaccinated against HBV. HIV and HCV serology results were negative for all participants. All five subjects were referred to the Clinical Department of the Spallanzani Institute for antimalarial treatment.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eA 6% prevalence rate of malaria infection was observed among asymptomatic male migrants from SSA countriesThe longest residence in Italy among positive cases was 181 days with a median parasite survival of approximately five months, but extended to 18 months when including detention periods in Libya. Asymptomatic co-infections with schistomiasis and latent tuberculosis, and previous HBV exposure is reported, reflecting the endemic nature of these infections in their origin countries\u003csup\u003e\u003cspan additionalcitationids=\"CR9 CR10\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe persistence of \u003cem\u003ePlasmodium\u003c/em\u003e infection in humans is not well-documented, with studies reporting durations from 6 to 386 days for blood-stage infections of \u003cem\u003eP. falciparum\u003c/em\u003e\u003csup\u003e\u003cem\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/em\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Asymptomatic carriers, despite lacking typical symptoms like fever, act as reservoirs and can facilitate parasite transmission in non-endemic regions with suitable vectors, posing significant challenges to malaria control efforts. The recent re-emergence of \u003cem\u003eAnopheles sacharovi\u003c/em\u003e in Apulia, thought to be extinct in Italy for over 50 years, highlights the growing receptivity of Italian southern regions and underscores its public health implications\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eWith approximately 8,000 imported cases of malaria reported annually in Europe, the potential for \u003cem\u003ePlasmodium\u003c/em\u003e transmission by gametocyte carriers arriving from endemic regions remains a significant public health concern\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Screening strategies for malaria vary considerably across countries. In Italy, guidelines implemented in July 2015 recommend the use of RDTs for symptomatic migrants, while PCR testing is reserved for high-risk groups, including pregnant women and immunocompromised individuals\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. These variations in screening practices reflect differences in national and international asylum policies. Compared to microscopy and RDTs, PCR testing demonstrates superior sensitivity, particularly for detecting low-level parasitaemia in asymptomatic individuals, highlighting its utility as a screening modality for migrants originating from malaria-endemic areas\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eItaly received approximately 225,000 refugees and migrants by sea between 2023 and 2024\u003csup\u003e17\u003c/sup\u003e, primarily from Burkina Faso, Guinea, Cameroon, Ivory Coast, and Nigeria\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. In 2023, the country\u0026rsquo;s foreign resident population was 5.1\u0026nbsp;million, \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e with approximately 500,000 undocumented migrants. \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e These findings underscore the importance of implementing inclusive screening programs based on epidemiological data from both the country of origin and the migration route. The involvement of frontline healthcare workers and general practitioners is essential to effectively address the healthcare access barriers faced by asylum seekers, undocumented migrants, and, more broadly, mobile populations.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis study confirms that asymptomatic \u003cem\u003ePlasmodium\u003c/em\u003e infections may persist for several months after arrival in a non-endemic country, underscoring the long-term resilience of the parasite in the absence of clinical symptoms. The limited sensitivity of rapid diagnostic tests (RDTs), compared to molecular methods such as PCR, resulted in a significant underdetection of cases, raising concerns about the reliability of standard diagnostic approaches in low-transmission settings.\u003c/p\u003e\u003cp\u003eThe fact that infections were still detectable over six months post-arrival\u0026mdash;and more than 600 days since departure from endemic regions when accounting for prolonged transit and detention\u0026mdash;indicates that standard screening windows based on recent travel history may fail to identify chronic carriers.\u003c/p\u003e\u003cp\u003eOur findings strongly support the integration of PCR-based diagnostic strategies into routine screening protocols for migrants from malaria-endemic areas, particularly within comprehensive health assessments offered upon arrival and during follow-up. This approach would contribute to early detection, reduce the potential for local transmission (especially in receptive areas), and improve individual health outcomes.\u003c/p\u003e\u003cp\u003eMore broadly, these results point to the urgent need for inclusive and sustained infectious disease screening policies that are not limited to immediate post-entry checks but are tailored to the specific risk profiles and migration trajectories of mobile populations. Strengthening such policies is essential not only for individual case management but also for informed public health planning in increasingly multicultural and mobile societies.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eSSA\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eSub\u0026ndash;Saharan Africa\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eRDT\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eRapid Diagnostic Test\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003ePCR\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003ePolymerase Chain Reaction\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eHBV\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eHepatitis B Virus\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eHCV\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eHepatitis C Virus\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eHIV\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eHuman Immunodeficiency Virus\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eIGRA\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eInterferon Gamma Release Assay\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eHBsAg\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eHepatitis B Surface Antigen\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eHBcAb\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eHepatitis B Core Antibody\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eIQR\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eInterquartile Range\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003e\u0026bull; \u003cb\u003eCI\u003c/b\u003e\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eConfidence Interval\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics Approval and consent to partecipate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was approved by Ethical Committee of the Lazio Area 4 (44-2025). Informed consent was obtained from all subjects involved in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll patient gave informed consent for collecting personal data for research purposes.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed relating to this study are presented within this published article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by funds allocated to the National Institute for Infectious Diseases \u0026ldquo;Lazzaro Spallanzani\u0026rdquo;, IRCCS, 00149, Rome (Italy), from the Italian Ministry of Health (Linea 1 Malattie Infettive tropicali e neglette: aspetti patogenetici, immunologici e diagnostici, 2025-2027).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFF\u003c/strong\u003e and \u003cstrong\u003eSV\u003c/strong\u003e: conception and design of the study, data acquisition, and writing the original draft of the manuscript. \u003cstrong\u003eDK\u003c/strong\u003e: writing the original draft of the manuscript, data analysis, and interpretation of results. \u003cstrong\u003eTAB\u003c/strong\u003e, \u003cstrong\u003eSR\u003c/strong\u003e, \u003cstrong\u003eNB\u003c/strong\u003e, \u003cstrong\u003eGM, AC, ADA\u003c/strong\u003e: investigation, data acquisition and interpretation. \u003cstrong\u003eAV\u003c/strong\u003e and \u003cstrong\u003eBB:\u003c/strong\u003e experiment, analysis, interpretation of laboratory data and revision of the manuscript. \u003cstrong\u003eCF\u003c/strong\u003e: validation, writing, review and editing. \u003cstrong\u003eEN\u003c/strong\u003e: validation, writing, review, editing, supervision and funding acquisition. All authors read and approved the final version of the manuscript and agree to be accountable for all aspects of the work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMobile-INMI group: Elena Boschiavo, Patrizia De Marco, Maria Letizia Giancola, Alessandra Lamonaca, Andrea Mariano, Claudia Palazzolo, Sara Pantanella, Giuseppa Tarab\u0026ugrave;, Maria Virginia Tomassi.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWorld Malaria Report 2024: Addressing Inequity in the Global Malaria Response. Geneva: World Health Organization; 2024. Licence: CC BY-NC-SA 3.0 IGO.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBousema T, Okell L, Felger I, Drakeley C. Asymptomatic malaria infections: detectability, transmissibility and public health relevance. 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Integrazione, Asilo, Lavoro, Salute e Welfare, Religioni, Educazione e Intercultura, Europa, Statistica XXIX Rapporto Sulle Migrazioni 2023.\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":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"infectious-diseases-of-poverty","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"idop","sideBox":"Learn more about [Infectious Diseases of Poverty](http://idpjournal.biomedcentral.com)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/idop/default.aspx","title":"Infectious Diseases of Poverty","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Asymptomatic malaria, Plasmodium infection, Malaria screening, Migrant health screening, Infectious disease surveillance","lastPublishedDoi":"10.21203/rs.3.rs-6863865/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6863865/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cb\u003eBackground\u003c/b\u003e\u003c/p\u003e\u003cp\u003eSub-Saharan African (SSA) migrants may harbor asymptomatic \u003cem\u003ePlasmodium\u003c/em\u003e infections long after leaving endemic regions, representing a potential public health concern in host countries. However, data on the prevalence and persistence of such infections post-migration are limited.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMethods\u003c/b\u003e\u003c/p\u003e\u003cp\u003eBetween February 2024 and January 2025, SSA migrants attending the Lazzaro Spallanzani Institute\u0026rsquo;s mobile population clinic were screened for malaria using rapid diagnostic tests (RDTs), thick blood smears, and PCR. Eligibility criteria included age\u0026thinsp;\u0026ge;\u0026thinsp;16, absence of fever, and origin or transit through malaria-endemic regions. Additional screenings for tuberculosis, schistosomiasis, and viral hepatitis were also conducted.\u003c/p\u003e\u003cp\u003e\u003cb\u003eResults\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAmong 87 asymptomatic migrants tested, PCR detected \u003cem\u003ePlasmodium\u003c/em\u003e spp. in 5 cases (6.02%), while RDT identified 2 (2.29%). Identified species included \u003cem\u003eP. falciparum\u003c/em\u003e, \u003cem\u003eP. malariae\u003c/em\u003e, \u003cem\u003eP. ovale\u003c/em\u003e, and one mixed infection. The longest time since arrival among positive cases was 181 days; including detention in Libya, the median duration since departure from endemic areas was over 600 days.\u003c/p\u003e\u003cp\u003e\u003cb\u003eConclusions\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAsymptomatic malaria persists months after arrival and is underdetected by RDTs. PCR enhances diagnostic sensitivity, supporting its use in screening migrants from endemic areas. These findings highlight the need for inclusive, long-term infectious disease screening policies tailored to mobile populations.\u003c/p\u003e","manuscriptTitle":"Burden of asymptomatic malaria in Sub-Saharan migrants attending an outpatient clinic in Rome from February 2024 to January 2025.","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-14 11:40:28","doi":"10.21203/rs.3.rs-6863865/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-07-14T09:04:54+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-10T08:20:29+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-10T07:00:51+00:00","index":"","fulltext":""},{"type":"submitted","content":"Infectious Diseases of Poverty","date":"2025-07-09T04:20:12+00:00","index":"","fulltext":""},{"type":"decision","content":"Major revision","date":"2025-06-12T23:42:35+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"infectious-diseases-of-poverty","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"idop","sideBox":"Learn more about [Infectious Diseases of Poverty](http://idpjournal.biomedcentral.com)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/idop/default.aspx","title":"Infectious Diseases of Poverty","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"0f37301a-d27a-403a-a6d8-9e3571e07041","owner":[],"postedDate":"July 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-10-27T16:23:10+00:00","versionOfRecord":{"articleIdentity":"rs-6863865","link":"https://doi.org/10.1186/s40249-025-01379-5","journal":{"identity":"infectious-diseases-of-poverty","isVorOnly":false,"title":"Infectious Diseases of Poverty"},"publishedOn":"2025-10-23 16:16:41","publishedOnDateReadable":"October 23rd, 2025"},"versionCreatedAt":"2025-07-14 11:40:28","video":"","vorDoi":"10.1186/s40249-025-01379-5","vorDoiUrl":"https://doi.org/10.1186/s40249-025-01379-5","workflowStages":[]},"version":"v1","identity":"rs-6863865","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6863865","identity":"rs-6863865","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}