The Nigeria Centre for Disease Control and Prevention (NCDC) recorded 14 new confirmed cases between Aug. 10 and Aug. 16, bringing the cumulative number of confirmed infections in the country in 2026 to 1,035. Deaths had risen to 252 by epidemiological week 33.
The figures translate to a case fatality rate of 24.4 per cent, significantly higher than the 18.6 per cent recorded during the corresponding period in 2025.
The latest cases were reported in Ondo, Bauchi, Edo and Benue States, adding to a pattern of transmission that has repeatedly affected several states and communities across the country.
For health experts, however, the statistics tell only part of the story. Behind the numbers are patients whose early symptoms can be mistaken for malaria, families who may delay hospital visits, healthcare workers exposed to infection and communities living in environments where rodents can thrive.
When a familiar fever hides a dangerous disease
For Amina Peter’s family, Lassa fever did not initially look like a life-threatening disease.
When her fever persisted for several days, her relatives assumed she had malaria. They purchased over-the-counter medication and waited for her condition to improve.
Instead, her weakness became increasingly severe.
It was only then that the family took her to a hospital, where further testing was carried out.
Her experience illustrates one of the central challenges in Nigeria’s response to Lassa fever: the disease can begin with symptoms that resemble common illnesses, particularly malaria, potentially allowing patients to remain at home until their condition deteriorates.
Dr Eno Onen, a community physician at University College Hospital, Ibadan, said early symptoms of Lassa fever were frequently mild and could easily be mistaken for malaria.
He stressed the importance of maintaining a high level of clinical suspicion, particularly in states and communities where Lassa fever transmission is known to occur.
“My advice is this: if you experience fever lasting more than 48 hours that does not respond to malaria treatment, don’t manage it at home.”
Onen said persistent fever should prompt people to seek medical attention, especially where there has been possible exposure to rodents or contact with someone suspected of having the disease.
The warning is significant because untreated Lassa fever can progress from nonspecific symptoms such as fever, headache, weakness and stomach discomfort to much more serious complications.
In severe cases, patients may develop bleeding, facial swelling, breathing difficulties, confusion and seizures. The disease can ultimately become fatal.
How Lassa fever enters homes
Lassa fever is a viral haemorrhagic disease caused by the Lassa virus. Its principal reservoir is the multimammate rat, which can shed the virus through urine, droppings and other biological materials.
Humans can become infected through contact with contaminated food, water, household surfaces and environments.
According to Onen, rodent-to-human transmission accounts for the overwhelming majority of infections.
“Together, these rodent-to-human routes account for an estimated 90 percent to 95 per cent of human Lassa infections,” he said.
The remaining infections can occur through contact with the blood, urine, saliva and other body fluids of infected people.
This form of transmission presents a particular concern in healthcare environments, where inadequate infection prevention and control measures can expose health workers and other patients.
Environment plays a major role
Experts increasingly argue that Nigeria’s Lassa fever challenge cannot be separated from changes in the environment.
Dr Ekpereonne Esu, Associate Director of Cochrane Nigeria, linked part of the continuing transmission to ecological disruption in affected communities.
Deforestation, biodiversity loss and changing rainfall patterns, he said, can influence rodent populations and behaviour, potentially increasing contact between infected animals and humans.
Seasonal rainfall can also affect where multimammate rats seek food and shelter. When environmental conditions become less favourable in their natural habitats, rodents may move closer to human settlements and homes.
“Deforestation adds another dimension because expanding farmland into forested areas can create favourable conditions for rodents while simultaneously reducing natural habitats and disrupting ecological balance.
“Biodiversity loss, caused by human activities, reduces natural predators that ordinarily control rat populations, allowing the rodents to multiply and spread infections more easily,” Esu said.
Housing conditions can further increase the risk.
Cracks and gaps in walls, leaking roofs, poorly fitted doors and inadequate waste management can give rodents easy access to houses. Once inside, they can contaminate food, water and household surfaces.
The TETFund-sponsored Mega Research Project on Lassa fever also identified poor housing, rodent infestation, food contamination, leaking roofs and poorly fitted doors as significant environmental risk factors.
These findings reinforce the growing importance of a One Health approach to Lassa fever—one that recognises the links between human health, animal populations and the environment.
23 states affected
NCDC data showed that by epidemiological week 33, confirmed Lassa fever infections had been recorded in 23 states and 117 local government areas.
Although transmission remains concentrated in particular parts of the country, the geographical spread demonstrates that the disease remains a national public-health concern.
Bauchi, Ondo, Taraba, Benue and Edo accounted for 87 per cent of cumulative confirmed cases by week 33.
The weekly figures have not followed a consistent upward pattern.
Four new cases were recorded in week 32, compared with 17 in week 31, before the number increased again to 14 in week 33.
Similarly, week 30 recorded 17 cases after 20 cases in week 29, while 25 cases were recorded in week 28 following 14 cases in week 27.
Such fluctuations can make the outbreak appear less threatening during weeks when fewer cases are recorded. But health experts warn that a temporary decline does not mean transmission has stopped.
As long as new infections continue to emerge, the disease remains active and requires surveillance and prevention.
Why the fatality rate matters
The 24.4 per cent case fatality rate reported by week 33 is particularly concerning.
It suggests that significant challenges remain in the early recognition, diagnosis and management of severe disease, even as Nigeria continues to strengthen surveillance and outbreak-response systems.
Younger adults are among the groups frequently affected. Recent NCDC reports identified people aged 21 to 30 as the predominant affected age group, while research findings point to substantial exposure among adults aged 20 to 40.
Researchers have associated this pattern partly with farming and outdoor activities, which can increase contact with rodents and potentially contaminated environments.
Food storage practices can also contribute to exposure when food is kept in places accessible to rodents.
Searching for answers among survivors
While prevention and treatment remain immediate priorities, Nigerian researchers are also looking for answers in people who survive the disease.
At Abubakar Tafawa Balewa University Teaching Hospital in Bauchi, scientists are studying Lassa fever survivors to understand why some infected people recover while others develop severe disease or die.
Prof. Alash’le Abimiku, Executive Director of the International Research Centre of Excellence and Institute of Human Virology Nigeria, said the research could contribute to the development of an effective vaccine.
“We want to study survivors and understand what made them survive,” Abimiku said.
Researchers are examining survivors’ immune responses while also studying different Lassa virus lineages circulating in Nigeria.
The research programme goes beyond laboratory investigations. It includes community engagement, clinician training, improved diagnosis and laboratory studies, reflecting the need to connect scientific findings with practical public-health measures.
Abimiku also noted that Lassa fever was no longer strictly seasonal, with infections now being recorded throughout the year.
The shift strengthens the argument for continuous surveillance and prevention rather than relying primarily on seasonal responses.
TETFund-backed research seeks long-term solutions
The search for better tools to combat Lassa fever is also receiving institutional backing.
During the presentation of research findings, TETFund Executive Secretary Sonny Echono highlighted the need to accelerate the search for solutions, including vaccine development.
“What is the shortest route toward developing a vaccine? How can we ensure that the burden on our people is reduced?” Echono asked during the presentation of research findings.
He said TETFund would escalate validated findings to relevant authorities, including the NCDC and the Federal Ministry of Health.
The development could also strengthen proposals for establishing a vaccine development centre in Nigeria.
The Federal University of Health Sciences, Otukpo, received a N250 million Mega Research Grant for the project, which examined the epidemiology, diagnosis, management and control of Lassa fever.
Principal Investigator Joseph Okopi said Nigeria carried the highest global burden of the disease, estimating that between 5,000 and 10,000 people die from Lassa fever annually.
The study examined antibody prevalence, rodent vectors, transmission patterns and associated risk factors across five states.
Benue recorded the highest prevalence of Lassa fever antibodies among the populations surveyed.
Researchers assessed 1,266 participants and investigated 392 suspected cases in Benue and Kogi. Of these, 43 infections were confirmed by PCR—25 in Benue and 18 in Kogi.
Identifying patients at greatest risk
Researchers are also examining the clinical characteristics associated with severe outcomes.
Audu Onyemocho, Professor of Community Medicine and a Consultant in Public Health, said bleeding, older age and seizures emerged as strong predictors of mortality.
The findings could help clinicians identify patients who require urgent and intensive management before their condition deteriorates further.
The response must go beyond hospitals
The continuing Lassa fever burden highlights the limits of relying solely on hospitals and clinical treatment.
Experts say prevention must begin within communities, with measures aimed at reducing rodent exposure and improving sanitation and housing.
Families can reduce risks by keeping food in rodent-proof containers, maintaining clean surroundings, disposing of waste properly and sealing openings through which rodents can enter homes.
At the health-system level, rapid diagnosis, laboratory capacity, infection prevention and control, surveillance and timely treatment remain essential.
For health workers, strict precautions when handling suspected or confirmed cases are critical because person-to-person transmission can occur through contact with infected body fluids.
The scientific community, meanwhile, is pushing for stronger research into vaccines, immune responses, viral lineages and the environmental conditions that allow transmission to persist.
The challenge is therefore broader than controlling an outbreak after cases appear. It involves changing the conditions that allow the virus to move between rodents, households, communities and healthcare facilities.
For Nigerians like Amina Peter and her family, the lesson is immediate: a persistent fever should not automatically be assumed to be malaria.
Where symptoms do not improve after malaria treatment, particularly in areas where Lassa fever is known to circulate, early medical assessment can make a critical difference.
Lassa fever may begin quietly, but the response to it cannot.
With 1,035 confirmed infections and 252 deaths recorded by epidemiological week 33 in 2026, Nigeria faces a continuing challenge that requires early testing, prompt treatment, stronger surveillance, improved living conditions, protected health workers and sustained investment in research and vaccine development.