New Clade Ib Monkeypox Case Detected in Britain
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April 8, 2025 Hour: 7:55 am
The patient had no known travel history or links with previously confirmed cases in Britain.
On Monday, the UK Health Security Agency (UKHSA) informed that a confirmed human case of Clade Ib monkeypox has been detected in northeast England.
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The patient, diagnosed in March, had no known travel history or links with previously confirmed cases in Britain. All contacts have been followed up and no further cases have been identified. The UKHSA is now working to determine how the patient caught the infection.
All previous mpox cases in Britain have either traveled to an affected country or have a link to someone who had. Clade Ia and Ib mpox will no longer be classified as a high consequence infectious disease following a review of available evidence by the Advisory Committee on Dangerous Pathogens.
“However, the decision should not be interpreted as Clade I mpox no longer being of any public health consequence,” the UKHSA said, noting that the disease is still a public health emergency of international concern as defined by the World Health Organization (WHO).
Clade Ib mpox is a specific genetic subgroup within the broader Monkeypox virus (MPXV) classification. Monkeypox is a zoonotic virus in the Orthopoxvirus genus, which also includes the variola virus (smallpox). MPXV is divided into two main clades: Clade I (formerly Central African or Congo Basin clade) and Clade II (formerly West African clade). One of the most important features of Clade Ib mpox is its relatively high human-to-human transmissibility compared to other clades.
While Clade I overall tends to cause more severe disease than Clade II, Clade Ib has demonstrated the capacity to spread more efficiently in community settings, especially where close contact is common. This has raised public health concerns, especially in contexts where containment and surveillance measures are limited.
Recent outbreaks have shown that Clade Ib can sustain transmission chains without the need for animal reservoirs, a trait that makes containment more challenging. Clinically, Clade Ib mpox tends to cause more severe symptoms than Clade II, including higher rates of hospitalization and complications such as secondary bacterial infections, pneumonia, and encephalitis.
Patients infected with Clade Ib often present with fever, rash, and lymphadenopathy, but the severity and progression of symptoms can vary. Mortality rates for Clade I have historically been higher than for Clade II, though the actual fatality rate may vary depending on healthcare access and patient comorbidities.
Common symptoms of mpox include a skin rash or pus-filled lesions which can last two to four weeks. It can also cause fever, headaches, muscle aches, back pain, low energy and swollen lymph nodes.
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Sources: Xinhua – WHO