A new strain of mpox has been detected, UK health officials have warned, describing it as a mix of two major types of the virus, identified in someone who recently travelled in Asia.
BBC reports that officials are still assessing the significance of the latest strain, which appears to contain elements of clade Ib and clade IIb, and which currently has no name.
The UK Health Security Agency (UKHSA) says it is normal for viruses to evolve, and that getting vaccinated remains the best way to protect against severe disease – although an mpox infection is mild for many.
UK health officials recently encouraged gay and bisexual men to make sure they were vaccinated against mpox. That call came as the clade Ib strain showed early signs of local spread in some European countries.
Clade IIb is linked to the global outbreak of mpox in 2022 which affected many countries worldwide.
In the UK, vaccination is available for groups of people at highest risk of catching mpox:
- those who have multiple sexual partners;
- those who engage in group sex; and
- those who visit sex-on-premises venues.
Health officials say the vaccine is 75%-80% effective at protecting against mpox.
Dr Katy Sinka, head of sexually transmitted infections at UKHSA, said genomic testing had detected the latest strain, and that “further analysis will help us understand more about how mpox is changing”.
Professor Trudie Lang, director of the Global Health Network at the University of Oxford, said there were “excellent systems” to identify cases and control onward infection in Britain, but in other parts of the world, in more vulnerable populations, “this is harder to achieve”, where access to vaccines is not as reliable.
She said if further cases of this strain appeared in the UK and elsewhere, it would be important to understand how it was being spread and how ill it makes people, to be able to assess whether it was more or less dangerous than previous strains.
There have been nearly 48 000 confirmed cases of mpox globally in 2025, and 2 500 in the past month, with most occurring in central Africa.
Dr Boghuma Titanji, Assistant Professor of Medicine at Emory University, said the new strain is what experts feared would happen if mpox continued to spread worldwide.
“The more mpox circulation we permit, the more opportunities the virus has to recombine and adapt, further entrenching the virus as a human pathogen that is not going away,” she warned.
BBC News article – New mpox strain identified in England (Open access)
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