A retrospective analysis of 1,624 suspected Lassa fever cases in Ebonyi State, Nigeria (2019–2023) found a case fatality rate (CFR) of 39.2% among 273 confirmed cases — meaning 107 people died. CFR trended upward across the study period, ranging from 28.6% to 55.8%, though this increase was not statistically significant. Age above 44 years, bleeding, and seizures were independent predictors of mortality in multivariate logistic regression. Incidence peaked seasonally between January and March, and geographic spread expanded from 10 to 12 local government areas between 2019 and 2020.
These figures are alarming in global context. The World Health Organization typically reports Lassa fever CFRs of 15–25% in hospitalized patients, making Ebonyi's 39.2% substantially higher and suggesting possible delays in treatment-seeking, limited ribavirin availability, or healthcare system constraints. The seasonal January–March peak aligns with dry-season rodent behavior patterns, a long-established driver of human Mastomys exposure. The identification of older age as a mortality predictor echoes findings from other hemorrhagic fever cohorts, though mechanisms remain unclear. Critical limitations include reliance on passive surveillance data from the SORMAS platform, which likely undercounts true case burden, and the retrospective design cannot establish causality. Geographic expansion warrants close monitoring. As a preprint posted on medRxiv and not yet peer-reviewed, these findings should be interpreted cautiously — but the magnitude of the CFR signals an urgent need for targeted intervention in this high-burden region.