UK health authorities on Monday said they had detected 36 more cases of monkeypox in England and the first infection in Scotland.
The UK Health Security Agency (UKHSA) said the new cases took the total number of confirmed in England since May 7 to 56, but stressed that although the outbreak was concerning, the risk to Britons remained low.
British Prime Minister Boris Johnson said his government was looking carefully at the circumstances surrounding its transmission.
"It is basically a very rare disease and so far the consequences don’t seem to be very serious but it is important that we keep an eye on it," Johnson told reporters.
UKHSA repeated that the infection does not usually spread easily between people.
"Alongside reports of further cases being identified in other countries globally, we continue to identify additional cases in the UK," UKHSA's Chief Medical Adviser Dr. Susan Hopkins said in a statement.
"A notable proportion of recent cases in the UK and Europe have been found in gay and bisexual men so we are particularly encouraging these men to be alert to the symptoms."
The more than 100 suspected and confirmed cases in the recent outbreak in Europe and North America have not been severe, the WHO's emerging diseases and zoonoses lead and technical lead on COVID-19, Maria van Kerkhove, said earlier on the day.
UKHSA has advised that high risk close contacts of confirmed cases should isolate for 21 days.
(Reporting by Farouq Suleiman and Muvija M; editing by William James and Alistair Smout)