Two cases of Lassa fever have been identified in England, and a further probable case is under investigation, according to the UK Health Security Agency (UKHSA).
The cases are within the same family in the east of England and are linked to recent travel to West Africa, where the disease is endemic.
One of the sufferers has recovered and another is receiving specialist care at the Royal Free London NHS Foundation Trust.
The further probable case is being treated at Bedfordshire Hospitals NHS Foundation Trust and the UKHSA said “the High Consequence Infectious Disease Network is engaged with their ongoing care”.
What is Lassa fever?
According to the UKHSA, Lassa fever is an acute viral haemorrhagic illness caused by Lassa virus.
People usually become infected with Lassa virus through 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. It can also be spread through infected bodily fluids.
Prior to the most recent cases, there have been eight imported to the UK since 1980, the UKHSA said. The last two were in 2009 and there was no evidence of onward transmission from any of these.
Imported cases are almost exclusively among people who work in Lassa-endemic areas in high-risk occupations, such as medical or other aid workers.
According to the World Health Organization (WHO) Lassa fever is “known to be endemic in Benin, Ghana, Guinea, Liberia, Mali, Sierra Leone, and Nigeria, but probably exists in other West African countries as well.”
What are the symptoms?
According to the WHO, the incubation period of Lassa fever ranges from six to 21 days. The onset of the disease, when it is symptomatic, is usually gradual and begins with fever, general weakness, and malaise.
After a few days those with the fever may develop a headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhoea, cough, and abdominal pain.
According to the WHO: “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.”
About 80 per cent of people who become infected with Lassa virus have no symptoms.
The antiviral drug ribavirin appears to be an effective treatment for Lassa fever if given early in the course of the illness, the WHO says. There is currently no vaccine against the disease.
Should we be worried about the number of cases in England?
While most people with Lassa fever will make a full recovery, severe illness can occur in some individuals and it is fatal for between 1 and 3 per cent of cases.
Dr Susan Hopkins, chief medical advisor at UKHSA, said: “Cases of Lassa fever are rare in the UK and it does not spread easily between people.
“The overall risk to the public is very low. 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.
“UKHSA and the NHS have well-established and robust infection control procedures for dealing with cases of imported infectious disease and these will be reinforced.”
Dr Sir Michael Jacobs, consultant in infectious diseases at the Royal Free Hospital, in Hampstead, north London, said: “The Royal Free Hospital is a specialist center for treating patients with viral haemorrhagic fevers, including Lassa fever.
“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.”