Conference Abstract | Volume 8, Abstract ELIC2025298 (Poster 050) | Published: 31 Jul 2025
Okpachi Christopher Abbah1,2,&, Lorna Williams-Enenche1,2, Oladayo David Awoyale1,3, Idu Francis Ola2, Michael Onoja Amedu1,2, Vivian Nwechi2, Ubong Akpan Okon1,4, Oyeladun Okunromade1,2, Chioma Dan-Nwafor5, Ogunbode Oladipo1,2
1Nigeria Field Epidemiology & Laboratory Training Programme, Abuja Nigeria, 2Nigeria Centre for Disease Control and Prevention, Abuja Nigeria, 3Kwara State Ministry of Health, Ilorin, Nigeria, 4Public Health Information, Surveillance Solutions and Systems, Abuja, Nigeria, 5Africa Centres for Disease Control, Abuja, Nigeria
&Corresponding author: Okpachi Christopher Abbah, Nigeria Field Epidemiology & Laboratory Training Programme, Abuja, Nigeria. Email: theocabbah@gmail.com
Received: 30 Apr 2025, Accepted: 09 Jul 2025, Published: 30 Jul 2025
Domain: Infectious Disease Epidemiology
Keywords: Epidemiology, Public health surveillance, zoonoses, Lassa fever, Nigeria
©Okpachi Christopher Abbah et al. Journal of Interventional Epidemiology and Public Health (ISSN: 2664-2824). This is an Open Access article distributed under the terms of the Creative Commons Attribution International 4.0 License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Cite this article: Okpachi Christopher Abbah et al., Lassa fever trends in Nigeria (2019–2023): Insights from secondary surveillance data. Journal of Interventional Epidemiology and Public Health. 2025;8(ConfProc5):00194. https://doi.org/10.37432/JIEPH-CONFPRO5-00194
Lassa fever, a viral hemorrhagic zoonotic disease, has become increasingly endemic in Nigeria, with a concerning shift from seasonal to year-round transmission. This study analysed national Lassa fever trends from 2019 to 2023, examining the magnitude and distribution of cases by person, place, and time. The findings will inform public health policy and guide interventions to mitigate the impact of Lassa fever in Nigeria which shares borders with Benin Republic, Niger, Chad and Cameroon.
A secondary analysis was conducted using laboratory-confirmed Lassa fever line list data from the Nigeria Centre for Disease Control and Prevention’s Lassa Fever Technical Working Group. Frequencies and proportions were used to summarise demographics and test outcomes for data from 2019 to 2023. A confirmed case was defined as a suspected case that was positive by reverse transcriptase polymerase chain reaction (RT-PCR) using blood samples.
Between 2019 and 2023, a total of 33,815 suspected Lassa fever cases were reported with 4,757 (14.1%) confirmed, with an average annual incidence rate of 4.1 cases per 1,000,000 population. Most confirmed cases occurred in individuals aged 21 – 30 (26.9%), with slight male preponderance (53.8%). Cases spanned 95% of Nigerian states (n=37), including 94% of international border states (n=16) and 88% coastal states (n=8). Ondo and Edo States alone accounted for 66% (3,136) of all confirmed cases, highlighting persistent hotspots. Temporal analysis revealed continuous, year-round transmission, with seasonal peaks consistently observed between epidemiological weeks 3 and 10.
The study highlights the widespread and sustained transmission of Lassa fever in Nigeria, with a significant burden in Ondo and Edo states. The unrelenting year-round transmission underscores the need for sustained public health interventions. To mitigate the impact of Lassa fever, we recommend enhanced surveillance, targeted Interventions, cross-border collaboration and public awareness.
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