First UK case of mpox variant clade Ib detected in London

Health officials have reported the UK’s first case of mpox caused by a new strain that is driving an ongoing surge in infections in Africa.

The UK Health Security Agency said the individual tested positive for clade Ib mpox after travelling to countries affected by the outbreak and had been transferred to the high-consequence infectious diseases unit at London’s Royal Free hospital.

The person developed flu-like symptoms after returning to the UK on an overnight flight on 21 October. They later developed a rash and were swabbed for the virus after attending an emergency department in London on 27 October.

The UKHSA and partner organisations are now tracing the person’s close contacts, who will be offered mpox tests, vaccination, and healthcare advice should they be found to have the virus.

“This is the first time we have detected this clade of mpox in the UK, though other cases have been confirmed abroad,” said Prof Susan Hopkins, the UKHSA’s chief medical adviser.

“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,” she added. “Investigations are under way to learn how the individual acquired the infection and to assess whether there are any further associated cases.”

Evidence suggests that mpox clade Ib causes more serious illness than mpox clade II, which sparked the 2022 global outbreak of the disease, previously known as monkeypox. Clade II has been circulating at low levels in the UK since 2022, primarily among gay, bisexual and other men who have sex with men.

The UKHSA said it was working closely with the NHS and academics to further assess the health risks of clade Ib.

Last month, the UK ordered more than 150,000 doses of mpox vaccine to boost its preparedness after the World Health Organization declared the outbreak in Africa a global health emergency.

The strain emerged in the Democratic Republic of the Congo and spread to neighbouring countries. Cases have been detected in Burundi, Rwanda, Uganda, Kenya, Sweden, Germany and India.

Mpox can be passed on through close contact with an infected person, infected animals, or contaminated materials. Common symptoms include a skin rash or pus-filled lesions, which last up to a month.

The virus can cause fever, headaches, muscle aches, back pain, low energy and swollen lymph nodes. The disease is typically mild but can be fatal for some individuals.