Epidemiology and characteristics of cases with monkeypox virus clade I in the WHO European Region, 2024 to 2025

BACKGROUND A public health emergency of international concern (PHEIC) was declared in August 2024 following a sharp increase in mpox cases linked to the emergence of monkeypox virus (MPXV) clade Ib. AIM We aimed to characterise imported and locally acquired mpox clade I cases reported in the WHO European Region (WHO/Europe) since August 2024 and assess transmission patterns and response measures. METHODS We collected data on MPXV clade I infections reported by countries in WHO/Europe through the International Health Regulations. We contacted reporting countries to collect age, sex, travel history, most likely route of transmission, clinical course, contacts and type of exposure, and implemented control and prevention measures. RESULTS Between 14 August 2024 and 23 November 2025, 82 cases of MPXV clade I infection were reported; 45 were imported and 37 were infected in reporting countries. Seventy-nine were typed as clade Ib and two as clade Ia. Most imported cases reported heterosexual (n = 26) or close physical contact (n = 5) as possible exposure. Secondary transmission occurred in six households. One healthcare worker was infected. Since October 2025, further 17 autochthonous male cases were most likely infected through sex with other men. CONCLUSION Imported cases of MPXV clade I infection were associated with limited household transmission. The increase in autochthonous infections among men with recent sexual contact with other men suggests undetected spread in Europe, that may become sustained. Continued surveillance, case and contact investigation are needed to understand MPXV clade I epidemiology and drivers of MPXV clade I transmission in Europe.