Lassa Fever: 469 Cases, 109 Dead in 9 Weeks
Nigeria has recorded 469 confirmed cases of Lassa fever and 109 deaths in the first nine weeks of 2026, with the case fatality ratio climbing to 23.2 per cent, a significant increase from the 18.7 per cent recorded during the same period in 2025, according to the Nigeria Centre for Disease Control and Prevention.
The NCDC disclosed in its Week 9 Epidemiological Report covering February 23 to March 1 that 65 new confirmed cases were documented during the reporting period, representing a decline from the 77 cases registered in Week 8. The new infections were reported across Benue, Ondo, Bauchi, Taraba, Edo, Plateau and Nasarawa states.
The disease control agency noted that six healthcare workers contracted the virus during Week 9, bringing the cumulative total of infected medical personnel to 37 since the beginning of the year, raising concerns about infection prevention and control protocols in treatment facilities across affected states.
“Between Week 1 and Week 9 of 2026, Nigeria recorded 2,446 suspected cases of Lassa fever, of which 469 were confirmed, and four were classified as probable,” the NCDC stated in the report.
The centre observed that 86 per cent of all confirmed cases were concentrated in five states, specifically Bauchi, Ondo, Taraba, Benue and Edo, while the remaining 14 per cent were distributed across 13 other states with confirmed infections. A total of 18 states spanning 69 local government areas have reported at least one confirmed case since January 2026.
The epidemiological data revealed that the predominant age group affected by the disease was 21 to 30 years, with the male-to-female ratio for confirmed cases standing at 1:0.8, indicating a slightly higher infection rate among males compared to females.
Lassa fever is an acute viral hemorrhagic illness transmitted to humans primarily through contact with food or household items contaminated with urine or feces of infected Mastomys natalensis rodents, commonly known as multimammate rats. Person-to-person transmission can also occur through direct contact with blood, urine, feces, or other bodily secretions of an infected individual, particularly in healthcare settings where infection prevention protocols are inadequate.
The disease was first identified in 1969 in Lassa town, Borno State, northeastern Nigeria, when two missionary nurses died from the infection. Since then, Nigeria has experienced seasonal outbreaks, typically peaking during the dry season between November and May when rodent populations migrate closer to human settlements in search of food and shelter.
According to the World Health Organisation, Lassa fever is endemic in several West African countries including Nigeria, Sierra Leone, Liberia and Guinea. Nigeria accounts for the majority of reported cases in the region due to its large population and widespread presence of the Mastomys rodent vector. The disease has an incubation period of six to 21 days, and symptoms range from mild fever, headache and malaise to severe manifestations including hemorrhaging, respiratory distress, facial swelling, shock and multi-organ failure.
The NCDC, established in 2011 and upgraded to a full agency status in 2018 following the passage of the NCDC Act, serves as Nigeria’s national public health institute responsible for detecting, investigating and responding to disease outbreaks. The agency coordinates the national response to epidemic-prone diseases including Lassa fever, cholera, yellow fever, meningitis and emerging infectious threats.
In response to the escalating outbreak, the NCDC confirmed that the national Lassa fever Incident Management System has been activated to coordinate multi-sectoral response efforts involving government agencies, international partners and health organizations. The agency stated that intensified case searches, contact tracing activities and deployment of national rapid response teams to seven high-burden states have been initiated to contain transmission.
“Personal protective equipment and other response materials have been distributed to treatment centres, while a targeted infection prevention and control ring strategy was launched in Benue State with support from the World Health Organisation,” the NCDC noted.
The centre disclosed that field missions and clinical support activities are being conducted with technical assistance from international partners including Médecins Sans Frontières and the United States Centres for Disease Control and Prevention, reflecting the collaborative approach required to manage the outbreak effectively.
However, the NCDC identified several critical challenges undermining response efforts, including late presentation of cases to healthcare facilities, poor health-seeking behavior among affected populations due to the high cost of treatment, inadequate environmental sanitation in affected communities, and the increasing number of infections among healthcare workers.
Late presentation remains a particularly acute problem, as many patients only seek medical attention after developing severe symptoms, reducing treatment effectiveness and survival chances. The antiviral drug ribavirin has been shown to be effective in treating Lassa fever when administered early in the course of illness, but delayed diagnosis and treatment initiation significantly diminish its therapeutic impact.
The high cost of treatment poses a substantial barrier to early health-seeking behavior, particularly in rural communities where the majority of cases occur. Patients often delay visiting healthcare facilities due to financial constraints, opting instead for traditional remedies or self-medication until symptoms become life-threatening. This pattern contributes to higher mortality rates and increased community transmission as infected individuals remain in contact with family members and neighbors.
Inadequate environmental sanitation in affected communities continues to facilitate rodent proliferation and human-rodent contact. Poor waste management, open food storage, inadequate housing structures with gaps allowing rodent entry, and lack of access to clean water create conditions conducive to Mastomys rat breeding and survival. These structural determinants of health require sustained investment in community infrastructure beyond immediate outbreak response.
The rising number of healthcare worker infections highlights persistent gaps in infection prevention and control practices within treatment facilities. Healthcare workers face elevated risk due to direct contact with infected patients and contaminated materials, particularly when adequate personal protective equipment is unavailable or improperly used. The loss of healthcare workers to infection further strains already limited health system capacity in affected states.
The NCDC urged state governments to strengthen year-round community engagement in Lassa fever prevention, emphasizing that outbreak response must be complemented by sustained public health education, environmental sanitation improvements and rodent control measures during non-outbreak periods.
The agency specifically advised healthcare workers to maintain a high index of suspicion for Lassa fever, particularly when evaluating patients presenting with fever, headache and other nonspecific symptoms during the transmission season. Early referral of suspected cases to designated treatment centres and strict adherence to infection prevention and control procedures were emphasized as critical protective measures.
Nigeria’s Lassa fever burden has shown an upward trajectory in recent years, with the 2023 outbreak recording 1,140 confirmed cases and 227 deaths across 28 states, representing the highest annual toll in the country’s documented history of the disease. The 2024 outbreak saw 1,154 confirmed cases and 190 deaths across 27 states, while the 2025 outbreak recorded 987 confirmed cases and 178 deaths across 25 states, according to NCDC year-end reports.
The current 23.2 per cent case fatality ratio represents a concerning increase compared to recent years and exceeds the WHO benchmark case fatality rate of approximately 15 per cent for hospitalized Lassa fever patients. The elevated mortality rate suggests either increased disease severity, delayed treatment initiation, or gaps in clinical management capacity across treatment centres.
Public health experts have consistently advocated for strengthened surveillance systems, improved diagnostic capacity, enhanced laboratory networks and investment in research for Lassa fever vaccines and therapeutics as long-term solutions to reduce Nigeria’s disease burden. Several vaccine candidates are currently in various stages of development, but none has yet received regulatory approval for widespread use.
The NCDC continues to publish weekly epidemiological reports to ensure transparency and facilitate evidence-based decision-making by state governments, healthcare providers and development partners. The agency maintains active surveillance across all 36 states and the Federal Capital Territory through a network of designated Lassa fever treatment centres and diagnostic laboratories.