UK officials are checking for any possible cases of Lassa fever after a traveller to England, who has since returned to Nigeria, is known to have been infected.
The virus does not spread easily between people, and the overall risk to the public is very low, experts advise.
Anyone yet to be contacted by the UK Health Security Agency (UKHSA) is very unlikely to have had any exposure, they say.
In some West African countries, where the disease is endemic, people usually become infected through exposure to food, or household items contaminated with urine or faeces of rats.
Lassa fever is rare in the UK, but there have been a small number of cases before – most recently in 2022.
UK officials say they are “well-equipped to identify people who have Lassa fever” to limit any spread of infections.
The UKHSA says it is “working at speed” to find anyone who may have had contact with the person who had Lassa fever.
Dr Meera Chand, deputy director at the UK Health Security Agency, said: “Our health protection teams are working at pace to get in touch with people who were in contact with this individual while they were in England, to ensure they seek appropriate medical care and testing should they develop any symptoms.
“The infection does not spread easily between people, and the overall risk to the UK population is very low.”
People who are found to have Lassa fever will receive supportive treatment, meaning that they will be provided with fluids, monitored for their symptoms, and treated with medications depending on which symptoms they have. There is not currently an effective single treatment for the disease.