Nigeria's Lassa Fever Case-Fatality Rate Reaches 18%

 The Federal Republic of Nigeria continues confronting a multi-year outbreak of Lassa fever that is causing substantial fatalities. According to the Nigeria Centre for Disease Control and Prevention (NCDC) Epidemiological Week 50, the Case Fatality Rate (CFR) rose to 18.2%

The CFR is higher than the 16.5% recorded during 2024.

As of December 14, 2025, a total of 1,097 confirmed cases with 201 deaths have been reported during 2025. Confirmed cases have been reported in 21 States, with most cases reported from Ondo, Bauchi, Edo, and Taraba.

The virus was later identified in the town of Lassa, Nigeria, in 1969, and has become endemic in parts of West Africa, particularly Guinea, Liberia, Nigeria, and Sierra Leone, where the animal reservoir, the Mastomys rat, is common. Infected rats shed the Lassa virus in their urine and faeces.

Without an approved Lassa fever vaccine candidate available in 2025, the U.S. CDC recommends various travel vaccinations before visiting the West African country of Nigeria.