Home / News / Lassa fever: 3 dead in UK - All you need to know about viral infection

Lassa fever has reportedly claimed three lives in Britain, where the cases of new viral infection were detected last week. The UK Health Security Agency (UKHSA) in a statement on February 11 had said the number of cases of Lassa fever under investigation was 3.

On February 9, the health agency said the three cases were within the same family in the east of England and were linked to recent travel to West Africa.

What is Lassa fever?

Lassa fever is an acute viral haemorrhagic illness caused by Lassa virus. It is a zoonotic disease, meaning that humans become infected from contact with infected animals. The animal reservoir, or host, of Lassa virus is a rodent of the genus Mastomys, commonly known as the “multimammate rat." Mastomys rats infected with Lassa virus do not become ill, but they can shed the virus in their urine and faeces.


People usually become infected with Lassa virus through exposure to food or household items contaminated with urine or faeces of infected rats – present in a number of West African countries where the disease is endemic. The virus can also be spread through infected bodily fluids.

Though to a lesser extent, secondary human-to-human transmission can also occur through direct contact with the blood, secretions, organs or other body fluids of infected persons, especially in health-care settings, according to the WHO. 

There is no epidemiological evidence supporting airborne spread between humans. Person-to-person transmission occurs in both community and health-care settings, where the virus may be spread by contaminated medical equipment, such as re-used needles. Sexual transmission of Lassa virus has been reported.


The UK health agency said most people with Lassa fever will make a full recovery. However, severe illness can occur in some individuals. The cases of Lassa fever are rare in the UK and it does not spread easily between people, said Dr Susan Hopkins, chief medical advisor at UKHSA, adding that the overall risk to the public is very low.


The incubation period of Lassa fever ranges from 6–21 days. The onset of the disease, when it is symptomatic, is usually gradual, starting with fever, general weakness, and malaise. After a few days, headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhoea, cough, and abdominal pain may follow. 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.


The WHO said the antiviral drug ribavirin seems to be an effective treatment for Lassa fever if given early on in the course of clinical illness. There is no evidence to support the role of ribavirin as post-exposure prophylactic treatment for Lassa fever. 

There is currently no vaccine that protects against Lassa fever.

Prior to these three cases, there have been eight cases of Lassa fever imported to the UK since 1980. The last two cases occurred in 2009. There was no evidence of onward transmission from any of these cases.

Lassa fever in Nigeria

The WHO on Monday informed that in Nigeria, from 3 to 30 January 2022, 211 laboratory confirmed Lassa fever cases including 40 deaths (case fatality ratio: 19%) have been cumulatively reported in 14 of the 36 Nigerian states and the Federal Capital Territory.


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