WHO confirms new mpox recombinant strain detected in India and UK

The World Health Organization confirmed in February 2026 that a novel recombinant mpox virus strain has been detected in cases reported from India and the United Kingdom. Whole-genome sequencing showed the strain carries genetic material from both clade Ib and clade IIb, two branches of the mpox virus that had not previously been documented recombining in human cases. The strain has demonstrated the ability to replicate and potentially transmit between people, which is why the WHO took the finding seriously enough to extend its mpox standing recommendations under the International Health Regulations through August 2026.

A recombinant virus is not a new concept in virology, but it is a new development in mpox surveillance. Recombination occurs when two different viral strains infect the same cell simultaneously and exchange genetic material during replication. The result is a hybrid virus with characteristics that may differ from either parent strain. Whether those differences make the new strain more transmissible, more severe, or more resistant to existing vaccines is the central question WHO and national health authorities are now trying to answer.

What clade Ib and clade IIb are and why combining them matters

Mpox virus has two major clades, which are genetically distinct lineages. Clade I, which includes clade Ia and clade Ib, originates from Central Africa and has historically been associated with higher case fatality rates. In the Democratic Republic of Congo, clade Ib drove a significant outbreak beginning in 2023, with the WHO declaring a public health emergency of international concern over mpox in August 2024 specifically because of clade Ib's spread in DRC and neighboring countries. The clade Ib outbreak in eastern DRC was characterized by higher transmissibility through sexual contact than earlier clade I outbreaks had been.

Clade IIb is the lineage responsible for the 2022 global outbreak that spread to over 100 countries outside Africa, ultimately infecting more than 90,000 people in the United States alone by the end of 2023, according to CDC surveillance data. Clade IIb was associated with lower case fatality rates than clade I but high transmissibility through close physical contact. Existing vaccines, including the Jynneos two-dose vaccine authorized by the FDA, were primarily evaluated against clade IIb.

How the recombinant strain was detected in India and the UK

Whole-genome sequencing of mpox samples from cases in India and the UK identified the hybrid genetic signature that confirmed the recombinant nature of the strain. Routine sequencing of mpox samples is not uniformly practiced across all countries, which means the recombinant strain could be present in additional locations without yet having been detected. The UK Health Security Agency and India's National Centre for Disease Control both submitted sequencing data to WHO after the anomalous genomes were identified, which is the standard pathway for flagging novel variants under the International Health Regulations.

The specific cases involved individuals with travel histories or contact networks that connected regions where both clade Ib and clade IIb had been circulating. A person co-infected with both strains, or exposed to an environment where both strains were present, would provide the biological conditions for recombination to occur during viral replication within a single host. The WHO has not publicly detailed the epidemiological circumstances of the specific cases to protect patient privacy.

What WHO's extension of standing recommendations means

The WHO's standing recommendations under the International Health Regulations are a formal public health tool that sits below the level of a public health emergency of international concern but carries real obligations for member states. Under the current standing recommendations, countries are expected to maintain surveillance for mpox cases, sequence samples from confirmed infections, vaccinate high-risk populations, and share epidemiological and genomic data with WHO. Extending those recommendations through August 2026 keeps that infrastructure active while WHO's emergency committee assesses the significance of the recombinant strain.

The WHO emergency committee is specifically tasked with evaluating whether the recombinant strain has properties that meaningfully change the public health risk profile of mpox. The key variables are transmissibility compared to either parent clade, clinical severity in infected individuals, and whether existing vaccines and treatments retain their effectiveness against the hybrid strain. Tecovirimat, the antiviral drug used to treat severe mpox cases, has a mechanism of action targeting a viral protein that is highly conserved across orthopoxviruses, which means it is less likely to lose effectiveness due to recombination events than vaccines, which train the immune system to recognize specific viral surface proteins.

The broader mpox context in early 2026

Mpox has not disappeared from global surveillance since the 2022 outbreak. The CDC continued to record several hundred cases per month in the United States through 2024 and into 2025, primarily in men who have sex with men who had not completed the two-dose Jynneos vaccination series. In Africa, the situation was more serious. The Africa CDC reported over 60,000 mpox cases across the continent in 2024, with DRC accounting for the majority of both cases and deaths. Clade Ib's spread in eastern DRC and into Burundi, Rwanda, and Uganda drove the WHO's August 2024 emergency declaration.

The detection of a recombinant strain in countries as geographically separated as India and the UK adds a new layer of complexity to global mpox monitoring. It suggests that individuals exposed to clade Ib through travel or contact with the eastern DRC outbreak may have also had prior clade IIb infection or exposure, creating the conditions for recombination. The WHO's next emergency committee review of the mpox situation is scheduled for March 2026, where the recombinant strain's epidemiological data will be formally assessed alongside updated case counts from DRC and the global surveillance network.