The UK Health Security Agency (UKHSA) has identified a new recombinant mpox virus in England in an individual who had recently travelled to Asia.
Genomic sequencing showed that the mpox genome contained elements of clade Ib and IIb mpox. UKHSA says this is not unexpected as both clades are circulating, but highlights the continued potential for mpox virus to evolve and the importance of continued genomic surveillance. UKHSA continues to assess the significance of the strain.
Dr Katy Sinka, Head of Sexually Transmitted Infections at UKHSA, commented: “Our genomic testing has enabled us to detect this new mpox strain. It’s normal for viruses to evolve, and further analysis will help us understand more about how mpox is changing.”
The UK has a routine mpox vaccination programme in place for eligible groups, including those who have multiple sexual partners, participate in group sex, or visit sex-on-premises venues. Studies show the vaccine is around 75% to 80% effective in protecting against mpox.
UKHSA has shared its findings with relevant international partners, including the World Health Organization (WHO), to support global monitoring efforts.
In October 2025, there were small numbers of locally-acquired cases of clade Ib mpox in the USA, Spain, Italy, the Netherlands and Portugal which had no connection to countries with known clade Ib mpox transmission. This suggests there is now community transmission of clade Ib mpox globally. Most of the new cases identified in Europe and the USA have been in gay, bisexual and other men who have sex with men, a population in which clade Ib mpox transmission has not previously been observed.
Mpox is usually a mild infection, and clade Ia and Ib mpox are no longer classified as a high-consequence infectious disease (HCID). However, it can be severe in some cases.
Common symptoms of mpox include a skin rash or pus-filled lesions which can last 2 to 4 weeks. It can also cause fever, headaches, muscle aches, back pain, low energy and swollen lymph nodes.