Nigeria’s Lassa fever outbreak has recorded another rise in infections, with the Nigeria Centre for Disease Control and Prevention (NCDC) confirming 14 new cases in epidemiological week 33.
The latest figures pushed the country’s cumulative number of confirmed infections to 1,035, while the death toll rose to 252, according to the agency’s latest situation report made available in Abuja on Tuesday.
The new infections were recorded between August 10 and August 16 in Ondo, Bauchi, Edo and Benue states, highlighting the continued concentration of the disease in several states where Lassa fever has remained a persistent public health threat.
The increase also pushed the case fatality rate (CFR) to 24.4 per cent, significantly above the 18.6 per cent recorded during the corresponding reporting period in 2025.
“The 14 new cases represented an increase from four cases reported during epidemiological week 32, when cases were recorded in Ondo and Edo states.
“In week 32, cumulative infections reached 1,021, with 240 deaths and a case fatality rate of 23.5 per cent,” it said.
Despite the latest increase, weekly infections have continued to fluctuate. The four cases recorded in week 32 represented a sharp decline from the 17 confirmed cases reported in week 31, underscoring the unpredictable pattern of transmission.
The NCDC said the disease had spread across a substantial portion of the country, with 23 states recording at least one confirmed case in 117 local government areas as of week 33.
Bauchi, Ondo, Taraba, Benue and Edo continued to account for the overwhelming majority of infections.
“Bauchi, Ondo, Taraba, Benue and Edo states accounted for 87 per cent of all confirmed cases recorded cumulatively by week 33.
“The five states also accounted for 86 per cent of confirmed cases in week 32, maintaining their position as the major affected states.
“People aged 21 to 30 years remain the predominant age group affected by Lassa fever during both reporting weeks,” the agency said.
The latest report also showed no new infections among healthcare workers during the two reporting periods under review. According to the NCDC, no healthcare worker was newly infected in week 32, while week 33 also recorded no new healthcare worker infection.
The agency said it would continue surveillance and response activities across affected states as Lassa fever remained a significant public health concern.
Persistent national challenge
Lassa fever has remained a recurring health challenge in Nigeria, with outbreaks recorded across several states and deaths reported annually.
Nigeria recorded 790 confirmed cases and 148 deaths between January and June 29, 2025, according to an NCDC situation report.
The country also recorded a significant burden of the disease in 2024. An NCDC report showed that 806 confirmed Lassa fever cases were recorded during the first quarter of that year, with 150 deaths attributed to the disease during the period.
The scale of the outbreak has also varied considerably from year to year. According to the NCDC, Nigeria recorded 8,542 suspected cases, 1,170 confirmed cases and 200 deaths across 28 states in 2023.
The confirmed cases represented a 9.7 per cent increase compared with the number recorded in 2022.
What is Lassa fever?
Lassa fever is an acute viral haemorrhagic illness caused by the Lassa virus. The NCDC identifies the multimammate rat, commonly referred to as the African rat, as the primary reservoir of the virus.
Transmission to humans can occur through contact with food or household items contaminated with the urine or faeces of infected rodents. Human-to-human transmission can also occur, particularly in healthcare settings where infection-prevention and control measures are inadequate.
The disease can initially present with symptoms that resemble other common illnesses, making early recognition difficult.
Symptoms may include fever, headache, sore throat, general weakness, cough, nausea, vomiting, diarrhoea, muscle pain and chest pain.
In severe cases, the disease can progress to bleeding from body openings, including the ears, eyes, nose and mouth.
The continued rise in confirmed infections and fatalities has renewed attention on the need for sustained surveillance, early diagnosis, effective infection prevention and control, and rapid response across affected communities.
With cases now reported across 23 states, health authorities face the challenge of preventing further transmission while improving early detection and treatment for people infected with the virus.