UK health authorities on Monday said they had detected a case of the mpox variant clade 1b in which the patient had no reported travel history or contact with other infected people.
Efforts were ongoing to determine where the individual, who lives in northeastern England, may have caught the infection, the UK Health Security Agency (UKHSA) said in a statement.
All previously confirmed cases had either travelled to an affected area or had links to someone who had done so, it said.
UKHSA mpox incident director Gillian Armstrong said the "risk to the UK population from mpox remains low” despite the unexplained case.
Mpox is a viral disease related to smallpox, and has two main subtypes — clade 1, which mainly affects children, and clade 2.
Symptoms include fever, a skin rash or pus-filled blisters, swollen lymph nodes, and body aches.
The WHO first declared an international public health emergency in 2022 over the spread of clade 2. That outbreak mostly affected gay and bisexual men in Europe and the United States.
Vaccination and awareness drives in many countries helped stem the number of worldwide cases, and the WHO lifted the emergency in May 2023 after reporting 140 deaths out of around 87,400 cases.
In 2024, a two-pronged epidemic of clade 1 and clade 1b, a new strain, spread widely in the Democratic Republic of Congo.
The new strain has also been recorded in neighboring Burundi, Kenya, Rwanda, and Uganda, with imported cases in Sweden, India, Thailand, Germany, and the UK.
Fewer than 10 cases of mpox clade 1b have been confirmed in England between last October and February 13, according to the UKHSA.
