Lassa fever trends and outcomes from 2018 to April 2025 in Ebonyi State, Nigeria: A descriptive analysis of surveillance data

Introduction: Lassa fever remains a major public health threat in West Africa, with Nigeria bearing a substantial burden of the disease. Ebonyi State, in southeastern Nigeria, is a recognized hotspot, and the Alex Ekwueme Federal University Teaching Hospital Abakaliki (AEFUTHA) serves as the region’s principal treatment centre and a designated site for a Phase 2b Lassa fever vaccine clinical trial. This study described trends and outcomes among confirmed Lassa fever cases to generate epidemiological insights that can strengthen surveillance and inform the design and planning of future clinical research in endemic settings. Methods: We conducted a retrospective descriptive study of confirmed Lassa fever cases reported in Ebonyi State from January 2018 to April 2025. Data was sourced from Ebonyi State Ministry of Health surveillance records and AEFUTHA’s Lassa fever treatment register. All 416 confirmed cases were analyzed using IBM-SPSS version 25 to assess temporal trends, age and sex distribution, seasonal patterns, geographic origin, survival and case fatality rates. Results: Males accounted for 56.5% of cases. The most affected age groups were 31–40 years (105/416; 25.2%) and 21–30 years (102/416; 24.5%). The overall case fatality rate was 38.5% (160/416), with higher annual rates observed in 2025 (11/19; 57.9%) and 2023 (33/58; 56.9%). Seasonally, 83.7% (348/416) of cases occurred between January and March. Geographically, 96.9% (403/416) originated from Ebonyi State, with a few referrals from neighbouring states. Abakaliki Local Government Area accounted for nearly half of all cases (199/416; 47.8%), followed by Izzi (47/416; 11.3%) and Ezza North (46/416; 11.1%). The highest annual number of confirmed cases was recorded in 2020 (90/416; 21.6%), with lower counts observed in subsequent years. Conclusion: This eight-year trend analysis describes key epidemiological patterns of confirmed Lassa fever in Ebonyi State and provides evidence to support the strengthening of surveillance and planning of clinical research in an endemic setting. By identifying high-burden age groups, seasonal peaks, and geographic hotspots, the study offers contextual insights for prioritizing prevention, improving clinical care, and informing future research in Lassa fever–endemic settings.