A person in England has been diagnosed with the monkeypox virus, the UK Health Security Agency has said.
The patient had recently travelled to Nigeria, where they are believed to have caught the virus before coming to the UK, the health agency said.
They are now being treated at an expert infectious disease unit at Guy's and St Thomas' NHS trust in London.
Monkeypox is a rare viral infection from which most people recover in a few weeks, according to the NHS.
The UKHSA said monkeypox does not spread easily between people and the risk to the wider public was very low.
In an update published on Saturday, the health agency said: "As a precautionary measure, UKHSA experts are working closely with NHS colleagues and will be contacting people who might have been in close contact with the individual to provide information and health advice."
The first-ever recorded occurrence of the virus in the UK was in 2018, and since then a handful of cases have been confirmed by health authorities.