The WHO confirmed that two cases of the recombinant strain – combining genomic elements of clades Ib and IIb of monkeypox virus (MPXV) – have been identified to date: one in the UK and one in India. Both patients had recent travel histories and neither experienced serious illness.
No secondary cases were found after contact tracing.
WHO has published a detailed update on the two cases and the national responses.
Recombination is a natural process that can occur when two related viruses infect the same person and exchange genetic material, producing a new variant.
According to the WHO, detailed genomic analysis shows that the two individuals “became sick several weeks apart with the same recombinant strain,” suggesting that additional undetected cases may exist.
What is mpox?
Mpox is an infectious disease caused by monkeypox virus (MPXV), part of the Orthopoxvirus genus, which also includes the virus that causes smallpox.
It is spread through close physical contact, including sexual contact, and in some cases through contaminated materials or respiratory droplets.
Symptoms typically include fever, swollen lymph nodes, and a rash and/or lesions.
Click here to the WHO fact sheet on mpox.
Two detected cases
The case in the United Kingdom was discovered in December 2025 in a traveler returning from an Asia Pacific country. Initial laboratory studies identified the virus as clade Ib, but whole genome sequencing later showed that it contained genetic regions from both clade Ib and clade IIb strains. Repeated sequencing confirmed the results and showed that the virus “can replicate and presents potential for further transmission.”
In Indiaone patient who developed symptoms in September 2025 was initially classified as infected with clade II MPXV. However, following updates to global genomic databases, the virus was reclassified as the same recombinant strain identified in the UK. The Indian case represents the earliest known detection of this strain.
“Due to the small number of cases found to date, conclusions about transmissibility or clinical characterization of mpox due to recombinant strains would be premature, and it is still important to be aware of these developments” said the WHO.
Clinical presentations in both cases were consistent with known mpox infections.
Risk assessment unchanged
WHO’s overall risk assessment remains unchanged: The risk is assessed as moderate for men who have sex with men with new and/or multiple partners and for sex workers or others with multiple casual sexual partners, and low for the general population without specific risk factors.
At the same time, the WHO warned that clade differentiation PCR tests alone “may not reliably identify recombinant MPXV strains”, meaning that genomic sequencing is essential for detection.
“All countries should remain aware of the possibility of MPXV genetic recombination,” WHO said, calling for continued epidemiological surveillance, sequencing, vaccination of risk groups, and infection prevention and control measures.
The WHO stated that no travel or trade restrictions are warranted based on current information.
