UK detects first case of mpox variant clade 1b, says health agency

An infection with the latest mpox variant, clade 1b, has been detected in the United Kingdom for the first time, the UK Health Security Agency (UKHSA) announced on Wednesday.

The agency said that the single case was detected in London after the person returned from Africa, adding that the risk to the wider population "remains low".

UKHSA said the person had been on holiday and travelled back to the UK on an overnight flight on October 21.

They developed flu-like symptoms more than 24 hours later and, on October 24, started to develop a rash which worsened in the following days.

The person attended an emergency department in London on October 27, where they were swabbed, tested and sent home to isolate while waiting for the results.

They are currently being treated at an infectious diseases unit.

Fewer than 10 people who are thought to have come into contact with the patient are being traced, the UKHSA said.

"The risk to the UK population remains low, and we are working rapidly to trace close contacts and reduce the risk of any potential spread," said the agency's chief medical adviser Susan Hopkins.

Mpox, a viral disease related to smallpox that causes fever, body aches, swollen lymph nodes and a rash that forms into blisters, has two main subtypes -- clade 1 and clade 2.

From May 2022, clade 2 spread around the world, mostly affecting gay and bisexual men in Europe and the United States. In July 2022, the WHO declared an international public health emergency, its highest level of alarm over the spread.

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 roughly 87,400 cases.

But in 2024, a new two-pronged epidemic broke out mainly in the DRC.

As well as clade 1, which mainly affects children, a new strain emerged in the DRC, called clade 1b. Clade 1b cases have also been recorded in nearby Burundi, Kenya, Rwanda and Uganda -- none of which had previously detected mpox.

Single cases have also been detected in Germany, Sweden and Thailand.

The WHO declared another international emergency in August.