After a review of evidence, the UK Health Security Agency (HSA) said today that it no longer classifies clade 1a and 1b mpox as a high-consequence infectious disease.
In a statement, the HSA said its Advisory Committee on Dangerous Pathogens determined that the clade no longer meets the criteria for a high-consequence infectious disease, because it doesn't have a high mortality rate or lack available interventions.
However, the HSA emphasized that the decision doesn't mean clade 1 mpox no longer poses a public health threat.
Emma Richards, HSA's incident director, said, "There is now firm evidence of vaccine effectiveness and a low mortality rate for cases of clade I mpox, alongside heightened clinical awareness of symptoms, and access to rapid diagnostic testing and safe therapies with emerging evidence of efficacy."
Though the illness is mild for many, it can cause severe symptoms, including unusual blisters, fever, and headache, she said, adding that most people with infections reported close physical contact before symptoms began, such as massages or sexual activity. "It's important people who have travelled to affected countries in Africa remain alert to the risks and seek medical advice if necessary."
More evidence shows Tpoxx ineffective for clade 2 mpox
In related news, a trial of tecovirimat (Tpoxx) for clade 2 mpox infection supported by the US National Institutes of Health (NIH) showed that the drug, approved for treating smallpox with hopes that it would be useful for treating mpox, is safe but ineffective, the NIH's National Institute for Allergy and Infectious Diseases (NIAID) said in a statement last week.
Researchers stopped the trial in late 2024 after an interim analysis showed that Tpoxx monotherapy was ineffective in the study population. They presented more detailed results at the 2025 Conference on Retroviruses and Opportunistic Infections (CROI) in San Francisco.
The international trial, which began in 2022, found that the drug didn't reduce the time to clinical resolution or improve pain control in adults. The lack of effectiveness was also seen in a trial that was conducted in the Democratic Republic of the Congo.
Jeanne Marrazzo, MD, MPH, NIAID director, said the study advances the understanding of the disease and potential treatments. "We are grateful to the study team and participants for their contributions to groundbreaking research on a disease that we still do not know enough about."
