{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,5]],"date-time":"2026-11-05T13:10:44Z","timestamp":1793884244752,"version":"4.7.0"},"reference-count":25,"publisher":"Korea Disease Control and Prevention Agency","issue":"4","license":[{"start":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T00:00:00Z","timestamp":1782691200000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":["ophrp.org"],"crossmark-restriction":true},"short-container-title":["PHRP"],"published-print":{"date-parts":[[2026,8,31]]},"abstract":"<jats:p>Objectives: We examined national temporal trends, laboratory-confirmation performance, and climate associations in Lassa fever surveillance in Nigeria from 2020 to 2025, and assessed the impact of the coronavirus disease 2019 (COVID-19) pandemic on surveillance metrics. Methods: We analyzed 307 consecutive weeks of national Lassa fever surveillance data using an ecological study design. Primary outcomes included confirmed-case counts, case fatality rate (CFR), and laboratory-confirmation rate (LCR). Temporal trends were evaluated using regression models, climate associations using correlation and negative binomial regression analyses, and the impact of COVID-19 using interrupted time-series analysis. Results: Overall, 47,029 suspected cases, 6,288 confirmed cases, and 975 deaths were reported. The mean LCR was 11.2% (standard deviation, 7.2%), declining from 18.4% in 2020 to 9.9% in 2025 (p &lt;0.001). The overall CFR was 15.5%, with no significant downward trend over time. Confirmed cases were inversely associated with weekly rainfall (rs=\u22120.589, p &lt;0.0001) and positively associated with mean temperature (rs=0.462, p&lt;0.0001). Peak season incidence was 5.3-fold higher than that during off-peak periods. The COVID-19 lockdown period was associated with an immediate reduction in confirmed cases without a corresponding reduction in suspected cases. Conclusion: Lassa fever surveillance in Nigeria from 2020 to 2025 was characterized by a declining LCR, persistently elevated CFR, and a climate-linked seasonal pattern of increasing intensity, findings that are consistent with, but do not definitively establish, systemic underascertainment. CFR trends may partly reflect case-mix variation and detection bias. Because of the ecological study design, causal inferences cannot be drawn. These findings underscore the need for resilient, climate-informed, One Health surveillance systems.<\/jats:p>","DOI":"10.24171\/j.phrp.2026.0226","type":"journal-article","created":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T08:43:14Z","timestamp":1782722594000},"page":"310-321","update-policy":"https:\/\/doi.org\/10.24171\/crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Temporal dynamics, climate associations, and surveillance performance of Lassa fever in Nigeria, 2020\u20132025: a national longitudinal analysis"],"prefix":"10.24171","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6334-3850","authenticated-orcid":true,"given":"Ayokunle John","family":"Tadema","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-3431-8757","authenticated-orcid":true,"given":"Faith 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a seasonal-trend decomposition procedure based on LOESS","author":"Cleveland","year":"1990"},{"key":"ref21","first-page":"e0005766","volume-title":"An unplanned consequence of the Ebola emergency: Lassa fever collateral damage","author":"Bonwitt","year":"2017"},{"key":"ref22","doi-asserted-by":"publisher","DOI":"10.4161\/viru.24041"},{"key":"ref23","doi-asserted-by":"publisher","DOI":"10.3390\/microorganisms13061419"},{"key":"ref24","doi-asserted-by":"publisher","DOI":"10.1186\/s12879-025-11262-1"},{"key":"ref25","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pntd.0013512"}],"container-title":["Osong Public Health and Research 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