BACKGROUND On 14 August 2024, WHO Director-General declared a public health emergency of international concern (PHEIC) following a sharp increase in mpox cases linked to the emergence of monkeypox virus (MPXV) clade Ib. We characterise imported and autochthonous cases of MPXV clade I reported in the WHO European Region since August 2024. METHODS Between 14 August 2024 and 23 November 2025, we collected key information of MPXV clade I infections reported by member states of the WHO European Region through the International Health Regulations. We contacted reporting countries to collect, age, gender, travel history, most probable route of transmission, clinical course, number of contacts and type of exposure, and implemented control and prevention measures. RESULTS 82 cases of MPXV clade I infection were reported, including one probable; 45 were imported and 37 were infections acquired in Europe. Almost all were typed as clade Ib, except for two clade Ia. Most imported cases with information reported heterosexual or close physical contact as possible exposure. Secondary transmission occurred in six households, and one healthcare worker was infected. Since October 2025, 17 autochthonous cases have been reported with a majority men who reported recent sexual contact with other men in Europe. CONCLUSIONS Imported cases of MPXV clade I infection were associated with limited household but the increase in autochthonous infections among men with recent sexual contact with other men suggests MPXV clade 1b may be endemic in Europe. Continued surveillance, case and contact investigation are needed to understand MPXV clade I epidemiology and drivers of possible sustained transmission in Europe.
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Karagiannis et al. (2025) studied this question.
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