Nigeria’s Newest Lassa Fever Outbreak

Mar 14, 2018 | Deirdre Curran

Though Nigeria escaped the 2014-2016 Ebola outbreak relatively unscathed, the country is suffering through the latest Lassa fever outbreak. Since the beginning of 2018, the Nigerian CDC has reported 365 confirmed cases across 19 of Nigeria’s 36 states, with a case fatality rate of 24% among confirmed and probable cases.

International media outlets are finally turning their attention to Lassa fever and its impact in Nigeria, but often exaggerate the relative size and impact of this outbreak, neglecting to consider the broader context. For the past several years, Nigeria has reported a significant increase in confirmed cases and deaths from Lassa fever. There are several overlapping possibilities, including increased disease surveillance, demographic change, and climate change which extends the dry season. Within the context of recent outbreaks, this year’s case counts are not surprising but highlight the cracks in Nigeria’s public health infrastructure.

What is Lassa Fever?

Though Lassa fever is largely unknown in the United States, the viral illness causes an estimated 5,000 deaths per year in western Africa. Lassa is spread by the multimammate rat, which is endemic to the region and excretes the virus through its urine and feces. People can contract Lassa fever through ingestion or inhalation of rodent urine or droppings, commonly from eating contaminated food, touching soiled objects, or inhaling fecal particles spread in the air from sweeping. Not everyone displays symptoms, but patients that do have symptomatic illness will experience a combination of fever, weakness, headache, and muscle pain. About 20% of patients will develop hemorrhagic fever and organ failure, which can be fatal. The CDC estimates that between 15-20% of people who are hospitalized because of Lassa fever will die from the illness and its complications.

This year, the rats that carry Lassa fever may be more numerous, or more likely to harbor the virus. Photo: Simon Akam, Reuters

Current Situation

A total of 114 Lassa fever-related deaths have occurred since the start of the year. In addition to Nigeria, single cases have been reported in both Ghana and Liberia. Historically, disease surveillance across the region has been poor, and there may additional cases which have not been documented by public health authorities.

The WHO and other organizations are working to bolster local Nigerian public health capabilities, including the establishment of an Emergency Operations Centre in Abuja and additional bed capacity at critically-located hospitals.


As the dry season comes to a close, case counts are expected to decline and the outbreak will come to an end. Over the long term, the scale and impact of Lassa fever outbreaks and other communicable diseases will depend on the Nigerian and international community’s response. Nigeria’s public health infrastructure is weak, though improving slowly, particularly after the Ebola outbreak. However, there are only three laboratories in Nigeria that can test for Lassa fever, despite annual outbreaks which resulted in dozens of deaths.

Aside from Lassa fever, Nigeria regularly experiences outbreaks of meningitis, hepatitis E, and monkeypox, among other diseases. The country’s rural and semi-rural communities, including some outside the reach of government personnel, face the brunt of the communicable disease burden. Before we can see meaningful improvement, the government must be able to access, immunize, monitor, and treat patients in every community, and have the funds to do so. Travelers and workers in the area should be aware of the range of ongoing disease transmission and take appropriate precautions to prevent illness while in the region.