New Recombinant Strain of Mpox Identified in England, Raising Global Health Concerns
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A newly identified strain of mpox, combining elements of two previously known variants, has been detected in a traveler to Asia, prompting concern among public health officials about potential future spread.
Mpox, a virus related to smallpox, continues to pose a global health challenge, with experts now grappling with the emergence of a recombinant form that could complicate prevention efforts. Initial symptoms typically include fever, headache, muscle aches, and backache, often followed by swollen lymph nodes and exhaustion.Within days, a characteristic rash or sores can develop.
mpox virus currently circulating worldwide: Clade IIb and Clade Ib. Each presents distinct characteristics and risks.
Clade IIb Mpox: The 2022 Outbreak Strain
Clade IIb was responsible for the rapid global outbreak in 2022, infecting approximately 114,000 people and causing 220 deaths globally. The United States experienced a peak of 11,000 cases per month during the summer of 2022. While originating in animals, this clade demonstrated efficient person-to-person transmission, especially through sexual behavior among men who have sex with men. Clade IIb mpox is generally considered less severe, with a mortality rate of around 1%.
Clade Ib Mpox: A More Virulent Threat
In contrast, Clade Ib mpox causes more serious illness, with a fatality rate of approximately 10%. Historically found in the Democratic Republic of Congo (DRC) for many years,transmission was primarily from animals to humans through activities like butchering and consumption. However, a new outbreak beginning in the DRC in 2023 has shown increased person-to-person spread, including transmission within families and healthcare settings due to inadequate protective equipment. Notably, cases have been reported in children under 15, and, increasingly, through sexual contact – marking the first time Clade I mpox has been sexually transmitted, often involving heterosexual encounters, sex workers, and transient workers.
Between january and November 2025, over 48,000 cases of Clade ib mpox were reported in Central and Eastern Africa, with an additional 43 cases identified in other countries. While nearly half of these international cases involved recent travel to Africa, 24 occurred in individuals with no known travel history. The World Health Organization (WHO) now believes Clade Ib mpox is spreading locally in Italy,Malaysia,the Netherlands,Portugal,Spain,and the United States.
The Emergence of a Recombinant Virus
genomic testing has revealed that the individual in England is infected with a recombinant virus – a novel strain formed by the combination of genetic material from both Clade IIb and Clade Ib. Experts emphasize that this development is not entirely unexpected, as viruses constantly evolve, particularly when multiple strains are circulating together.
“The more mpox circulation we permit, the more opportunities the virus has to recombine and adapt, further entrenching mpox virus as a human pathogen that is not going away,” stated a senior official at Emory University, echoing widespread concerns about the virus’s adaptability. The primary worry is that viral evolution can hinder efforts to control and prevent further spread.
Vaccination remains a Key Defense
Fortunately, a vaccine, JYNNEOS, is available to protect against both mpox and smallpox. Administered in two doses, four weeks apart, vaccination reduces the risk of infection and transmission, and can lessen symptom severity if infection occurs.
The Centers for Disease Control and Prevention (CDC) currently recommends the mpox vaccine for gay, bisexual, transgender, or other men who have sex with men who have had or anticipate having one or more sexually transmitted infections, multiple sexual partners, anonymous sexual or intimate contact, sex at a commercial sex venue, or sex in association with a large public event in an area experiencing mpox transmission. A targeted vaccination campaign utilizing these criteria played a crucial role in curbing the spread of mpox in the United States in 2022.
Individuals meeting these criteria are urged to get vaccinated as soon as possible.While the new recombinant strain has not yet been detected in the United States, both Clade IIb and Clade ib continue to circulate at low levels.
