Nigeria Centre for Disease Control and Prevention (NCDC) has reported that the case fatality rate for Lassa fever rose to 19.3 per cent in 2026, up from 18.9 per cent recorded during the same period in 2025.
The agency disclosed this in its Lassa Fever Situation Report for Epidemiological Week 23, covering 1 to 7 June 2026.
According to the report, the number of newly confirmed cases remained unchanged from the previous week, with infections recorded in Edo, Ondo, Bauchi, and Ebonyi states.
The NCDC also noted that no new infections among healthcare workers were reported during the week under review. The outbreak spreads across 23 states.
The report showed that the outbreak has affected 23 states and 109 Local Government Areas (LGAs) since the beginning of the year.
It added that both suspected and confirmed cases have increased compared to figures recorded during the same period in 2025, indicating continued transmission of the disease.
According to the agency, five states account for the majority of confirmed infections nationwide. Ondo State recorded the highest burden, accounting for 28 per cent of confirmed cases, followed by Bauchi with 25 per cent, Taraba with 15 per cent, Edo with 10 per cent, and Benue with six per cent.
The remaining 16 per cent of confirmed cases were reported across 18 other states. Young adults are most affected.
The NCDC said young adults remain the most affected age group in the current outbreak.
It noted that the highest number of infections was recorded among persons aged between 21 and 30 years.
According to the report, confirmed cases ranged in age from 1 to 93 years, with a median age of 30 years. Response efforts ongoing
The agency said the National Lassa Fever Multi-Partner, Multi-Sectoral Incident Management System (IMS) remains activated to coordinate response activities across affected areas.
It explained that the system is supporting surveillance, case management, and other response interventions at the federal, state, and local government levels.
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Despite the absence of new healthcare worker infections in Week 23, the NCDC said the rising fatality rate and the continued spread of the disease across multiple states underscore the need for sustained response efforts.
It added that surveillance and case management activities are ongoing in all affected states to contain the outbreak and reduce deaths. Lassa fever
Lassa fever is an acute viral haemorrhagic illness caused by the Lassa virus, which is transmitted to humans primarily through contact with food or household items contaminated by the urine or faeces of infected rats.
It can also spread from person to person through contact with bodily fluids.
The disease often begins with fever, weakness, and headache, and may progress to more severe symptoms such as bleeding, difficulty breathing, swelling, and organ failure. Early diagnosis and prompt treatment with Ribavirin are critical for improving survival.