Lassa fever, a viral hemorrhagic illness spread primarily through infected rodents, is rapidly spreading across Nigeria, prompting urgent public health warnings and straining the nation’s healthcare system. According to the Nigeria Centre for Disease Control and Prevention (NCDC), as of the latest update covering the week of March 24–30, 2025, there have been 3,779 suspected cases of Lassa fever across the country.

Of these, 659 cases have been laboratory confirmed, with 122 reported deaths so far this year, giving the outbreak a case fatality rate of approximately 18.5%. In just one week, 300 new suspected cases were reported, along with three deaths, highlighting the growing severity of the outbreak. The disease, which in severe cases can cause internal bleeding from the mouth, nose, eyes, and other orifices, has been confirmed in at least 18 Nigerian states.

However, suspected cases have been identified in as many as 33 states, suggesting a much broader reach. The majority of confirmed infections—71%—have occurred in the states of Ondo, Bauchi, and Edo.

The NCDC reports that young adults, particularly those in their 20s, are most commonly affected. Due to the heightened risk to pregnant women, some hospitals have issued warnings advising pregnant healthcare workers to stay home during the outbreak.

Dr Edeth Nkantah, a physician at the Federal Medical Centre (FMC) in Jalingo and former chairman of the Nigerian Medical Association, told VaccinesWork: “All pregnant health workers have been asked to stay at home until the incidence of the disease comes down because Lassa fever is usually very severe in pregnant women.”

Healthcare workers have described the immense challenges they face while trying to care for patients with inadequate supplies of personal protective equipment (PPE). Dr Divine Njadze, who also works at FMC Jalingo, told VaccinesWork: “We may have up to 12 suspected Lassa fever cases in a day during the peak period. Different doctors see the patients at intervals, so the PPE is never enough. Sometimes we run out of PPE.”

She added: “Other times, we buy the PPE from our pockets. The National Association of Resident Doctors also provides packs of face masks for us. There's no prophylaxis for Lassa fever for now."

The current outbreak comes months after the NCDC first raised concerns in December 2024 about a spike in infections. By the end of 2024, the country had recorded 1,309 confirmed cases, with 214 fatalities.

The global health community is also on alert. In February 2025, a case of Lassa fever was confirmed in the United Kingdom in a patient who had recently returned from Nigeria, according to the UK Health Security Agency (UKHSA). The patient was diagnosed in England and isolated for treatment. The case has raised concerns about the potential for cross-border spread, although human-to-human transmission remains rare without direct contact with infected bodily fluids.

Lassa fever is caused by the Lassa virus, first identified in 1969 after two missionary nurses died in the town of Lassa, Borno State, Nigeria. The virus is endemic in parts of West Africa, including Nigeria, Guinea, Liberia, and Sierra Leone.

The disease primarily spreads through exposure to the urine, droppings, or saliva of Mastomys rats, a rodent species that is common across West Africa. Human infections typically occur after consuming contaminated food or inhaling airborne particles from rodent waste. Some individuals also catch the virus while preparing Mastomys rodents for food, a practice still seen in parts of Nigeria.

Though human-to-human transmission is rare, it can occur through direct contact with the blood, urine, faeces, or other bodily fluids of infected individuals, particularly in healthcare settings.

The illness often begins with mild symptoms, including fever, headaches, vomiting, diarrhoea, sore throat, and general weakness. However, in about 20% of cases, symptoms escalate, causing internal bleeding, multi-organ failure, respiratory distress, facial swelling, and neurological complications such as seizures.

While up to 80% of infections are asymptomatic or mild, severe cases can be deadly, particularly without prompt medical attention. There is currently no approved vaccine for Lassa fever, although research is ongoing.

Dr Fyne Akubueze, who leads Lassa fever response efforts at the Federal Medical Centre in Owo, Ondo State, emphasised the need for better protective measures and, ultimately, a vaccine.

“We hope there will be a vaccine soon to protect everybody, including health workers,” she told VaccinesWork. “But in the meantime, maintaining a high level of hygiene is very important aside from using PPE.”

Describing the precautions she takes, she said: “I have a bag at the entrance of my house where I put everything I wear when I return from work and wash them up. I do this to avoid putting my family in danger.”

The NCDC is continuing to coordinate with local governments and international health agencies to monitor and contain the outbreak. Public health experts stress the importance of rodent control, food safety, and awareness campaigns to reduce exposure risks in communities.