The first ever case of monkeypox has been recorded in the UK.
The rare viral infection was recorded on Friday in a Nigerian national staying at a naval base in Cornwall, Public Health England (PHE) said.
The patient was transferred to the expert infectious disease unit at the Royal Free Hospital in London on Saturday morning.
Swollen lymph nodes
They are believed to have contracted the infection in Nigeria before travelling to the UK.
PHE said monkeypox does not spread easily and most patients recover within a few weeks, but it can cause severe illness in some people.
Initial symptoms include fever, headache, aching muscles, backache, swollen lymph nodes, chills and exhaustion.
A rash can also develop, usually starting on the face before spreading to other parts of the body. It eventually forms a scab which falls off.
PHE said that as a precautionary measure, it is working with experts in the NHS to contact a number of people who were on the same flight as the patient.
The body has not revealed whether the patient is a member of the military, or confirmed their gender.
PHE said in a statement: "People without symptoms are not considered infectious but, as a precaution, those who have been in close proximity are being contacted to ensure that if they do become unwell they can be treated quickly."
The organisation said passengers that are not contacted need take no action.
Dr Michael Jacobs, clinical director of infection at the Royal Free Hospital, said: "Monkeypox is, in most cases, a mild condition which will resolve on its own and have no long-term effects on a person's health.
"Most people recover within several weeks.
"It is a rare disease caused by monkeypox virus, and has been reported mainly in central and west African countries.
"It does not spread easily between people and the risk of transmission to the wider public is very low.
"We are using strict isolation procedures in hospital to protect our staff and patients."
Dr Nick Phin, deputy director of the National Infection Service at PHE, said: "PHE and the NHS have well established and robust infection control procedures for dealing with cases of imported and infectious disease and these will be strictly followed to minimise the risk of transmission."