New Recombinant Mpox Strain Detected in UK and India, WHO Urges Vigilance

The World Health Organization (WHO) and national health agencies have confirmed the detection of a new recombinant mpox strain in the United Kingdom and India, underscoring the dynamic evolutionary nature of the virus and the persistent need for global genomic surveillance. This newly identified strain is a 'genetic mash-up' or hybrid, combining genomic elements from two known mpox strains: Clade Ib and Clade IIb of the monkeypox virus (MPXV). The WHO officially confirmed that two cases of this recombinant strain have been identified to date. The case in the United Kingdom was detected in December 2025 in a traveler returning from a country in the Asia Pacific region. Initial laboratory testing had categorized the virus as clade Ib, but subsequent whole genome sequencing revealed genetic regions from both clade Ib and clade IIb strains, confirming its recombinant nature. Repeat sequencing validated these findings and demonstrated the virus's ability to replicate, indicating its potential for onward transmission. In India, a patient who developed symptoms in September 2025 was initially classified as infected with clade II MPXV. However, following updates to global genomic databases and further analysis, the virus from this patient was reclassified as the same recombinant strain identified in the UK. Notably, the Indian case represents the earliest known detection of this specific recombinant strain. Both individuals affected by the recombinant strain had recent travel histories and experienced mild illness, with no reports of severe disease. Crucially, contact tracing did not identify any secondary cases linked to these two recombinant infections. Recombination is a natural biological process that can occur when two related viruses co-infect the same individual and exchange genetic material, leading to the creation of a new variant. Experts have long acknowledged the potential for such events, especially with the co-circulation of different mpox clades globally. The emergence of this inter-clade recombinant is considered a significant milestone in mpox virus evolution, demonstrating how sustained human-to-human transmission can create conditions for co-infection and genetic exchange between distinct mpox clades. Despite this development, the WHO has stated that the overall global public health risk assessment for mpox remains unchanged. However, the organization emphatically stresses the importance of continued genomic surveillance to detect new mpox variants early and to monitor for any signs of altered transmissibility or virulence that might necessitate updated public health measures or vaccine strategies. Due to the limited number of cases found to date, the WHO cautions against making premature conclusions about the transmissibility or clinical characteristics of mpox caused by these recombinant strains. Beyond these specific recombinant cases, mpox continues to be a global health concern. The WHO has twice declared a public health emergency of international concern (PHEIC) for mpox: first from July 2022 to May 2023, and again from August 2024 to September 2025, primarily due to outbreaks of Clade Ib in Africa. While the second PHEIC was declared over in September 2025, the WHO extended its standing recommendations for mpox until August 2026, highlighting the ongoing risk of sustained community transmission if outbreaks are not swiftly contained. Clade Ib, a more severe form of mpox, has been a particular focus of surveillance, with reports of its circulation in several countries outside Africa, including India. In India, for instance, ten mpox samples collected in Kerala between September 2024 and March 2025 were identified as Clade Ib through genomic analysis by the Indian Council of Medical Research-National Institute of Virology (ICMR-NIV) in Pune. Most of these cases were linked to recent international travel, though at least one case indicated probable local transmission. These findings confirm the presence of Clade Ib in India and emphasize the role of international travel in the introduction of new mpox strains. The ongoing detection of different mpox clades and subclades globally increases the likelihood of further recombination events, reinforcing the critical need for continuous vigilance and robust surveillance systems worldwide. Globally, the WHO reported nearly 48,000 confirmed mpox cases and 201 deaths across 94 countries by the end of October 2025. Countries like the UK have routine mpox vaccination programs for eligible groups to protect against severe disease. The establishment of a global mpox vaccine rapid deployment mechanism by 2026, through an ICG (International Coordinating Group) for mpox vaccine stockpile, is also underway to ensure timely and equitable access to vaccines for outbreak response and prevention. These efforts are crucial as the virus continues to evolve and circulate, demanding a coordinated global public health response.

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