Epidemiology of Lassa Fever Outbreaks Reported in Ondo State Between 2019 and 2024

Lassa fever is an acute viral haemorrhagic illness endemic to West Africa, caused by Lassa mammarenavirus and transmitted primarily through contact with Mastomys natalensis rodents. Ondo State in South West Nigeria consistently reports among the highest numbers of confirmed Lassa fever cases in the country. This study describes the epidemiological patterns of Lassa fever outbreaks in Ondo State from 2019 to 2024, using secondary surveillance data from the Nigeria Centre for Disease Control. A retrospective descriptive epidemiological analysis will examine case counts, case fatality rates, spatial distribution across local government areas, seasonal trends, exposure histories, and outcomes. Attack rates will be calculated for affected communities, and outbreak response timelines will be reviewed to identify delays in case investigation and contact tracing. The study will further examine the demographic profile of confirmed cases to determine which age groups and occupations are most affected. Recent reports indicate that Ondo State accounts for 20 to 30 percent of annual national Lassa fever case counts, with healthcare workers representing a significant proportion of cases. Findings will support the Ondo State Epidemiology Division in refining risk stratification strategies, optimising healthcare worker protection protocols, and strengthening rodent control measures in endemic communities. Keywords: Lassa fever, epidemiology, outbreak, Ondo State, case fatality rate