Nosocomial transmission in a monkeypox virus clade Ib outbreak, Ireland, August to October 2025.

In August-October 2025, an mpox outbreak with monkeypox virus clade Ib was identified in Ireland, involving four epidemiologically linked cases. The cluster originated from a traveller returning from Pakistan via the United Arab Emirates and includes a nosocomial infection. Phylogenetic analysis revealed genetic clustering with an Omani sequence, suggesting Eastern Mediterranean Region transmission routes. This outbreak underscores the importance of clinical vigilance, rapid molecular diagnostics and coordinated public health responses to prevent onward clade Ib transmission in non-endemic countries.