Geneva: The World Health Organisation has confirmed the emergence of a new recombinant strain of the monkeypox virus (MPXV), combining genetic elements of two different clades, raising fresh concerns about viral evolution and the need for enhanced genomic surveillance worldwide.
In a situation update issued on Friday, WHO said two cases of the recombinant mpox virus, containing genomic material from clades Ib and IIb, had been detected in recent months, one in the United Kingdom and the other in India.
Recombination is a natural biological process that occurs when two related virus strains infect the same individual and exchange genetic material, resulting in a new variant.
Genomic analysis showed that both patients were infected with the same recombinant strain, with illness occurring several weeks apart. The UK case involved a traveller returning from a country in South-East Asia, while the Indian case had travel links to the Arabian Peninsula.
The high degree of similarity between the two virus genomes suggests a shared evolutionary history and indicates that the recombinant virus may be circulating more widely than currently documented.
WHO said neither patient developed severe disease and no secondary cases were identified following contact tracing in either country. Clinical presentation in both cases was similar to that observed in infections caused by non-recombinant mpox clades.
However, the organisation warned that conclusions about transmissibility, severity or public health impact of the recombinant strain would be premature given the small number of cases detected so far.
The Indian case, retrospectively identified from samples collected in September 2025, represents the earliest known detection of this recombinant strain globally. Whole-genome sequencing showed more than 99.9 per cent similarity between the virus detected in India and the strain later identified in the United Kingdom, with multiple recombinant genomic segments shared between the two.
WHO said the emergence of recombinant mpox strains highlights the importance of genomic sequencing, noting that standard clade differentiation PCR assays may not reliably detect such recombinants.
The organisation warned that co-infection with different mpox strains, particularly within interconnected sexual networks across multiple countries, creates conditions in which viral recombination, although rare, can be expected.
The global public health risk assessment for mpox remains unchanged, WHO said. The risk continues to be assessed as moderate for men who have sex with men with new or multiple partners and for sex workers or others with multiple casual sexual partners, and low for the general population without specific risk factors.
The development comes amid ongoing mpox transmission in multiple regions.
In Pakistan, health authorities this month confirmed the country’s second mpox-linked death, underscoring the continued public health threat posed by the virus, particularly for individuals with underlying health conditions.
WHO has urged all countries to remain alert to the possibility of mpox genetic recombination and to strengthen surveillance, laboratory testing and genomic sequencing. The agency reiterated the need for robust infection prevention and control measures, targeted vaccination for populations at risk, and closer integration of mpox services with HIV and sexually transmitted infection programmes.
Based on current evidence, WHO said no travel or trade restrictions are recommended in response to the detection of the recombinant mpox strain, but stressed that the public health risk posed by any newly identified variant should be assessed on a case-by-case basis as more epidemiological and genomic data become available.
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