Lassa Fever Scourge

Lassa Fever Scourge

• Articles
• April 25, 2026

Ending the Scourge of Lassa Fever in Nigeria: Which Way Forward

Introduction

Lassa fever is an acute viral illness that is caused by the Lassa virus. It is a single-stranded RNA virus in the Arenaviridae family, transmitted primarily through contact with the urine and faeces of infected multimammate rats (Mastomys natalensis). This zoonotic origin explains the disease’s persistence in rural and peri-urban areas where humans live close to rodent populations.  

Historically, Lassa fever was first identified in 1969 in Lassa, Borno State, Nigeria, when two missionary nurses died from an unusual febrile illness in the town of Lassa, Borno State, Nigeria, it has since become an endemic viral disease with recurring outbreaks across the country.  Lassa fever has also spread to other parts of West Africa, including Benin, Ghana, Mali, Sierra Leone, Liberia, and Guinea. Annual outbreaks are most common during the dry season (November to April), although cases have increasingly been reported during the rainy season as well.

Over the decades, Nigeria has experienced multiple significant outbreaks. In 2018, the Nigeria Centre for Disease Control (NCDC) reported the largest number of cases to date, with over 600 confirmed cases and more than 170 deaths. Outbreaks continue to occur annually, with states such as Ondo and Edo consistently reporting high numbers of cases.

Lassa fever spreads primarily through rodent-to-human contact, including contaminated food, household items, or direct exposure to rodent excreta. However, to a much less extent, Lassa virus may also spread between humans through direct contact with blood, urine, faeces or other bodily secretions of a person infected with Lassa fever. Person-to-person transmission may occur primarily in health-care settings, where the virus may also be spread by contaminated medical equipment, such as re-used needles.

Challenges in controlling the disease include limited surveillance, inadequate public awareness, and insufficient rapid diagnostic capacity, which often delay detection and containment.  Factors contributing to fatalities include late healthcare seeking, limited early diagnosis, and high transmission in affected communities.

Clinical presentation

About 80% of people who become infected with Lassa virus have no or mild symptoms. One in 5 infections result in severe disease, where the virus affects several organs such as the liver, spleen and kidneys. The disease is characterized by high morbidity and mortality, with case fatality rates historically ranging from 3% to 42%, and more recently stabilizing between 20% and 25%.

When it is symptomatic, the onset of the disease is usually gradual, starting with fever, general weakness headache and malaise. After a few days, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhoea, cough and abdominal pain may follow. As the disease progresses, in severe cases facial swelling, fluid in the lung cavity, bleeding from the mouth, nose, vagina or gastrointestinal tract and low blood pressure may develop. Shock, seizures, tremor, disorientation, and coma may be seen in the later stages. Among hospitalized patients, approximately 15% die of Lassa fever disease. In fatal cases, death usually occurs within 14 days of symptom onset.

Diagnosis of Lassa fever

It can be difficult to clinically distinguish Lassa fever from other infectious diseases such as malaria, typhoid fever, shigellosis, yellow fever and other viral haemorrhagic fevers, especially early in the course of the disease. Confirmation that symptoms are caused by Lassa virus infection are made using the following diagnostic methods: (a) reverse transcriptase polymerase chain reaction (RT-PCR) assay (b) antibody enzyme-linked immunosorbent assay (ELISA) (c) antigen detection tests (d) virus isolation by cell culture.

Samples collected from patients are an extreme biohazard risk; laboratory testing on non-inactivated samples should be conducted under maximum biological containment conditions, therefore all non-inactivated biological specimens should be packaged using the triple packaging system when transported nationally and internationally.

Treatment of Lassa fever

There is currently no antiviral drug approved for Lassa fever. The antiviral drug ribavirin has been given as treatment for Lassa fever; however, there is currently considerable uncertainties about its efficacy on the outcome of patients with Lassa fever, as well as on its optimal dosing regimens. The best option where feasible would be to enrol patients into a randomized clinical trial with ribavirin or other investigational therapeutics to assess clinical outcomes and safety. Other candidate treatment options are at several stages of development and evaluation. There is currently no licensed vaccine for Lassa fever, but several potential candidate vaccines are in development. Managing the disease to improve survival chances requires early intensive supportive care including fluid management and treatment of specific symptoms.

Prevention and control of Lassa fever

Prevention of Lassa fever relies on limiting contact with rodent population. Promoting good community hygiene to discourage rodents from entering homes and adapting the following measures may help: (a) storage of grain and food in rodent-proof containers (b) maintaining a clean household including disposal of garbage far from home (c) safe preparation of food (e.g. by thoroughly cooking).

The animal reservoir, or host, of Lassa virus, the Mastomys rats infected with Lassa virus do not become ill, but they can shed the virus in their urine and faeces; however, since they are so abundant in endemic areas, it is not possible to eliminate them from the environment.

In healthcare settings, staff should always apply standard infection prevention and control precautions when caring for patients, regardless of their presumed diagnosis. These include basic hand hygiene, respiratory hygiene, use of personal protective equipment, and safe injection practices. Healthcare workers caring for patients with suspected or confirmed Lassa fever should apply extra infection control measures to prevent contact with the patient’s blood and body fluids and contaminated surfaces or materials such as clothing and bedding. Laboratory workers are also at risk. Samples taken from humans and animals for investigation of Lassa virus infection should be handled by trained staff and processed in suitably equipped laboratories under maximum biological containment conditions.

In endemic areas, especially during the epidemic season, health workers should have a higher level of suspicion for Lassa fever in patients presenting with suggestive symptoms. Family members should always be careful to avoid contact with blood and body fluids while caring for sick persons. Patients suspected or confirmed for Lassa fever should be referred to a designated treatment center for early care.

The current situation of Lassa Fever in Nigeria

As of early 2026, Lassa fever is spreading across Nigeria, with over 637 confirmed cases and 160 deaths reported. The outbreak has been reported in Edo, Bauchi, Ondo, Taraba, Kogi, Plateau, Ebonyi and Benue states with severe cases reported in in states like Bauchi, Ondo, Taraba, Benue, and Edo, which account for a significant portion of the cases. The case fatality rate has increased to 24.8%, indicating a worsening trend despite a decline in weekly confirmed cases. Health authorities are intensifying surveillance and infection prevention measures to manage the outbreak effectively.

Current interventions for Lassa fever in Nigeria

The current interventions for Lassa fever in Nigeria include a comprehensive approach to disease control and public health response. The key measures are:

(a) Integrated One Health Approach: This approach aims to improve disease control, reduce fatalities, and alleviate the economic burden of Lassa fever outbreaks. This measure involves the collaboration of various sectors to ensure effective management of the disease.

(b) Surveillance Systems: The Nigeria Centre for Disease Control and Prevention (NCDC) has implemented several surveillance systems, including state-level emergency operation centers and real-time reporting mechanisms, to enhance outbreak detection and response.

(C) Strengthening Public Health Infrastructure: This involves strengthening public health infrastructure such as treatment centres, surveillance systems, and community engagement to prevent and control Lassa fever outbreaks.

(d) Community Engagement: This measure involves the promotion of community awareness, building capacity for prevention, early detection, referral, and infection prevention and control measures.

(e) Vaccines and Civil Engagement: The Coalition for Epidemic Preparedness Innovations (CEPI) is working on developing Lassa fever vaccine candidates. There is also a civil society engagement initiative to support vaccine development and deployment.

(f) Treatment Decentralization: The decentralization of treatment of Lassa fever cases is being explored to optimize case management and outbreak responses, to address challenges such as patient behavior and facility congestion.

(g) Preventive Measures: The promotion of preventive measures such as proper food storage, environmental sanitation, and avoiding contact with rodents to reduce the risk of Lassa fever.

(h) Health Worker Training: WHO has supported the training of health workers and community volunteers to deliver prevention messages and answer questions effectively.

(i)  Vector Control: A vector control strategy in local communities is critical to dealing with this scourge.  The measures should include- setting rat traps, using rodenticides, and sharing health information on proper waste management and food preparation.

 

Conclusion and way forward in arresting this scourge

The identified interventions are part of a broader strategy to address the persistent nature of Lassa fever in Nigeria; they can help to improve the overall health outcomes of the population. These measures would help in reducing the transmission of the virus, and improve treatment outcomes, and ultimately save lives. The success of these efforts will however depend on continued collaboration and investment in public health infrastructure and education.