(LONDON) — Cases of Lassa fever have been identified in the United Kingdom for the first time in over a decade.

The U.K. Health Security Agency (UKHSA) confirmed in a press release Wednesday that two people have been diagnosed with Lassa fever in England, while a third “probable case” is under investigation.


All three cases are within the same family in the East of England and are linked to recent travel to West Africa, where the potentially deadly infectious disease is endemic.

“Cases of Lassa fever are rare in the U.K. and it does not spread easily between people. The overall risk to the public is very low,” Dr. Susan Hopkins, chief medical advisor at the UKHSA, said in a statement Wednesday. “We are contacting the individuals who have had close contact with the cases prior to confirmation of their infection, to provide appropriate assessment, support and advice.”

Hopkins noted that the UKHSA and the National Health Service (NHS) in England “have well established and robust infection control procedures for dealing with cases of imported infectious disease and these will be reinforced.”


Prior to these cases, there had been just eight cases of Lassa fever imported to the U.K. since 1980. The last two occurred in 2009. There was no evidence of onward transmission from any of these cases, according to the UKHSA.

Lassa fever is an acute viral hemorrhagic illness caused by Lassa virus. People usually become infected with Lassa virus through exposure to food or household items contaminated with urine or feces of infected rats that are present in parts of West Africa, according to the World Health Organization (WHO).

The virus can also be spread through infected bodily fluids. People living in endemic areas of West Africa with high populations of rodents are most at risk. Imported cases rarely occur elsewhere in the world and such cases are almost exclusively people who work in endemic areas in high-risk occupations, like medical or other aid workers, according to the UKHSA.


Lassa fever is known to be endemic in Benin, Ghana, Guinea, Libera, Mali, Sierra Leone, Togo and Nigeria, but probably exists in other West African nations as well. It’s not easy to distinguish from other viral hemorrhagic fevers, such as Ebola virus disease and malaria, and clinical diagnoses are often difficult, especially early in the course of the disease, because the symptoms are so varied and non-specific, according to the WHO.

Symptoms are usually gradual, starting with fever, general weakness and malaise. Then, after a few days, headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhea, cough and abdominal pain may follow. Patients with severe cases may develop facial swelling, fluid in the lung cavity, bleeding from the mouth, nose, vagina or gastrointestinal tract and low blood pressure. Deafness occurs in 25% of recovered patients and in half of these cases, hearing returns partially after one to three months, according to the WHO.

About 80% of people who become infected with Lassa virus have no symptoms and one in five infections result in severe disease, where the virus affects several organs such as the liver, spleen and kidneys. The overall case-fatality rate is 1%, while case-fatality among patients hospitalized with severe cases is estimated at around 15%. Death usually occurs within 14 days in fatal cases. Diagnosis and prompt treatment are essential, according to the WHO.


Although severe illness can occur in some individuals, most people with Lassa fever will make a full recovery, according to the UKHSA.

One of the patients with a confirmed case has recovered, while the other will receive specialist care at the Royal Free London NHS Foundation Trust, a London-based NHS foundation trust consisting of several hospitals and clinics. Meanwhile, the patient with the probable case is being treated at Bedfordshire Hospitals NHS Foundation Trust, which runs two hospitals in Bedfordshire county in the East of England. The U.K. High Consequence Infectious Disease Network is engaged with the ongoing care of the infected individuals, according to the UKHSA.

“The Royal Free Hospital is a specialist centre for treating patients with viral hemorrhagic fevers, including Lassa fever,” Dr. Sir Michael Jacobs, consultant in infectious diseases at the Royal Free London NHS Foundation Trust, said in a statement Wednesday. “Our secure unit is run by a highly-trained and experienced team of doctors, nurses, therapists and laboratory staff and is designed to ensure our staff can safely treat patients with these kind of infections.”


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