The case was detected in East Sussex and the individual is now under specialist care at Guy’s and St Thomas’ NHS Foundation Trust.
They had recently returned from Uganda, where there is currently community transmission of Clade Ib mpox.
It is the sixth case of Clade Ib mpox confirmed in England since October 2024 but the latest infection has no links to the previous cases identified in England.
UKHSA Deputy Director, Dr Meera Chand, said the risk to the UK population “remains low”.
The agency said on Monday it is checking the infected individual’s close contacts, with the help of partner organisations.
Contacts will be offered testing and vaccination where needed to prevent the infection spreading, the UKHSA said, and they will be told what, if any, further care is needed if they have symptoms or test positive.
Clade Ib mpox has been found in several countries in Africa in recent months and imported cases have been detected in several countries including Belgium, Canada, France, Germany, Sweden, and the US.
“Extensive planning” has been carried out so healthcare professionals are equipped and ready to respond to any further confirmed cases, the agency said.
The clade Ib variant is a new form of the virus linked to a global health emergency declared by the World Health Organisation in August.
Mpox, including the Clade 1b strain, is usually passed on by close physical contact, contact with infected animals or sexual transmission.
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Common symptoms of mpox include a skin rash or pus-filled lesions, which can last between two to four weeks.
It can also cause fever, headaches, muscle aches, back pain, low energy and swollen lymph nodes.
