Monkeypox has been diagnosed in the UK for the first time, a public health body warns.
The rare viral infection does not spread easily between humans and most people recover within a few weeks.
Public Health England (PHE) said the patient was a resident of Nigeria where the virus was probably contracted.
The patient had been staying at a naval base in Cornwall but is now being treated at the infectious diseases unit at the Royal Free Hospital in London.
Its experts are working closely with NHS colleagues "as a precautionary measure" and will be contacting people who might have been in close contact with the individual to provide information and health advice.
This includes contacting a number of passengers who travelled in close proximity to the patient on the same flight to the UK.
The patient travelled to London from Nigeria on 2 September and anyone who has not been contacted yet from that flight is advised no further action is required.
What is monkeypox?
- Monkeypox is usually a mild self-limiting illness and most people recover within a few weeks, however severe illness can occur in some individuals
- It is a rare disease caused by monkeypox virus, and has been reported mainly in central and west African countries
- The infection can be spread when someone is in close contact with an infected person, however there is a very low risk of transmission to the general population
- Initial symptoms include fever, headache, muscle aches, backache, swollen lymph nodes, chills and exhaustion
- A rash can develop, often beginning on the face, then spreading to other parts of the body. The rash changes and goes through different stages before finally forming a scab, which later falls off
Source: Public Health England
Dr Michael Jacobs, clinical director of infection at the Royal Free Hospital, said monkeypox "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," he added.
Dr Nick Phin, the deputy director of the National Infection Service at PHE, said: "It is important to emphasise that monkeypox does not spread easily between people and the overall risk to the general public is very low.
"Public Health England is following up those who have had close contact with the patient to offer advice and to monitor them as necessary."
He said PHE and the NHS have "well established and robust infection control procedures for dealing with cases of imported infectious disease and these will be strictly followed to minimise the risk of transmission".