Multimmate rat - a carrier of Lassa Fever in West Africa
A patient is being treated for Lassa fever at the high security infectious diseases unit at the Royal Free Hospital in London.
The Health Protection Agency say this is an isolated case in a 66 year old man who recently visited Nigeria.
They are trying to identify nurses and doctors at two other hospitals who cared for the man before the disease was identified.
Lassa fever is spread through direct contact with body fluids.
The HPA say the man came back to the UK on 6 January and two days later was admitted to Homerton University Hospital. The Homerton carried out tests and sent samples to the Health Protection Agency.
Two weeks later on the 22nd of January the patient was transferred to the Hospital for Tropical Diseases, University College Hospital.
It was there, on Thursday, that the diagnosis of Lassa fever was made and he was transferred to the Royal Free which is one of two national specialist hospitals which can deal with hazardous infections. The unit is sealed from the rest of the hospital and has its own filtered air supply.
LASSA FEVER SYMPTOMS
The hospital say the man is in a stable condition.
The HPA is working with the Homerton and University College Hospital to identify any members of staff who were involved in the care of the patient. They will be provided with information about Lassa fever and asked to get in contact if they develop any symptoms.
Lassa fever is an acute viral haemorrhagic fever cased by the Lassa virus. It lives on rats and spreads in their urine and droppings.
It causes hearing loss in 25% of victims and 1% of victims will die.
Dr Dilys Morgan, a Lassa fever expert at the HPS. said: "This is an isolated case of Lassa fever in a traveller who has recently returned from Nigeria. It is important to stress that there is no risk to the general public from this patient.
"Lassa fever is an infection that is found in West Africa and is seen rarely in this country in those who have travelled to parts of the world where it is common."
There have been 10 confirmed cases of Lassa fever in the UK since 1970.