First UK case of potentially deadly mpox strain detected in London

The first UK case of a potentially deadly strain of the mpox virus has been detected in London.

The UK Health Security Agency (UKHSA) said the risk to the UK population from the Clade Ib mpox strain “remains low”.

The person involved had been on holiday in Africa 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 have now been transferred to the Royal Free Hospital high consequence infectious diseases unit for treatment.

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

These are household contacts, although the UKHSA is “still working” on the number of people it may have to contact trace.

Mpox only spreads between people when there is close contact.

Spread may occur through direct contact with rash, skin lesions or scabs caused by the virus, including during sexual contact, kissing, cuddling or other skin-to-skin contact.

There is also a risk from contact with bodily fluids such as saliva or snot; contact with bedding or towels or clothing; and a possibility of spread through close and prolonged face-to-face contact such as talking, breathing, coughing, or sneezing.

Symptoms include skin rash with blisters, spots or ulcers that can appear anywhere on the body, fever, headache, backache and muscle aches.

A rash usually appears one to five days after a fever, headache and other symptoms.

Clade Ib mpox has been widely circulating in the Democratic Republic of Congo (DRC) in recent months and there have been cases reported in Burundi, Rwanda, Uganda, Kenya, Sweden, India and Germany.

A report from the World Health Organisation (WHO) and the Africa Centres for Disease Control and Prevention said there had been more than 40,000 mpox cases linked to almost 1,000 deaths in Africa as of the end of September 2024, with Clades Ia, Ib and II circulating in the region.

The WHO has declared a public health emergency of international concern because of the rapid spread of the mpox strain.

Professor Susan Hopkins, chief medical adviser at the UKHSA, said: “It is thanks to our surveillance that we have been able to detect this virus.

“This is the first time we have detected this Clade of mpox in the UK, though other cases have been confirmed abroad.

“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.”

According to the UKHSA, the UK has an existing stock of mpox vaccines and last month announced further vaccines are being procured.

Prof Hopkins said there is an “active management plan” for the new strain.

“Overall we are well prepared, and we have been preparing over the last number of weeks and months for mpox, with ensuring that we have the right diagnostic tests and developing a PCR test for this specific Clade,” she said.

“In addition, we have been buying vaccines, and have started to widen out our vaccines to individuals who have been higher risk for Clade II, particularly gay, bisexual and men who have sex with men in urban centres. And further vaccine will be coming into the country shortly.

“We have an active plan of management here, which includes contact tracing, particularly close contacts that an individual has been in contact with from their period of illness, and we will be seeking to ensure that we contact each of those individuals and isolate the relevant individuals for up to 21 days after the last exposure.

“Where we consider that there’s a high risk they will also be offered a vaccination, and that vaccination will be delivered with collaboration with the NHS.”

Prof Hopkins added that UKHSA will predominantly be looking for the strain in people who travel, but will also be testing all mpox cases picked up in sexual health clinics to determine what clade they are.

Speaking on the interventions, Prof Hopkins said: “We’ve got a very high level of alertness and awareness in the NHS, primary care, secondary care, through NHS 111, and through any other services that people may contact as a result of feverish illnesses, feeling unwell or having a rash, particularly after travel.”

She added that capacity for tests to detect the strain has been increased and vaccines have been prioritised for individuals where Clade II is circulating.

“In individuals of higher risk, gay, bisexual and men who have sex with men, the clinics that that has been prioritised for at this present time are London, Manchester and Brighton, where there are high proportions of gay, bisexual men who have sex with men attending sexual health clinics,” Prof Hopkins added.

“Finally, in individual cases, we will be contact tracing and offering people vaccine who are primary contacts of that case, but also potentially for those that may be contacts of those contacts where we consider a significant exposure may have occurred.”

When asked if the current vaccine is as effective on Clade Ib as it is on other strains, Prof Hopkins said: “We won’t be completely confident until we have large amounts of people who’ve been prevented get Clade I in the same way as we were able to do the Clade II studies.

“However, the licensing for this vaccine was done on animal studies for for Clade I mpox.

“It has been demonstrated in laboratory studies to be highly effective. There’s little difference between Clade Ia and clad Ib and therefore we expect there to be a good cross immunity.”

Health and Social Care Secretary Wes Streeting said the Government is working with UKHSA and the NHS “to protect the public and prevent transmission”.

“This includes securing vaccines and equipping healthcare professionals with the guidance and tools they need to respond to cases safely,” he added.

“We are also working with our international partners to support affected countries to prevent further outbreaks.”

This strain of mpox is different from mpox Clade II that 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 that while the existing evidence suggests mpox Clade Ib causes more severe disease than Clade II, it will continue to monitor it and learn more.

It said it will initially manage Clade Ib as a high consequence infectious disease.

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