Mpox due to monkeypox virus clade Ia infection detected outside of Africa: a case study

Abstract

Background: Monkeypox virus clade Ia has historically been restricted to central Africa and primarily associated with zoonotic transmission. In February 2025, a symptomatic adult with recent travel to the Democratic Republic of the Congo presented to a tertiary care facility in Ireland and was subsequently diagnosed with monkeypox virus clade Ia infection. We describe the clinical, laboratory, phylogenetic and epidemiologic features of this case. Methods: Diagnostic testing was performed on the 5th of February using real-time polymerase chain reaction. The patient was admitted to the National Isolation Unit, and comprehensive contact tracing with active surveillance was implemented. Whole-genome sequencing was performed to determine the viral lineage and conduct phylogenetic and mutation analyses. Results: The patient experiences a stable disease course and recovers without long-term complications. No secondary transmission is detected. Genomic analysis confirms infection with monkeypox virus clade Ia. The sequence clusters within the recently documented sh2024a outbreak in Kinshasa and displays APOBEC3-associated mutational signatures consistent with sustained human-to-human transmission. Conclusions: This case highlights changes in the global epidemiology of monkeypox virus clade Ia and underscores the need for enhanced surveillance and coordinated international public health responses. Early detection and monitoring by whole-genome sequencing are essential for mitigating the risks posed by possible expansion beyond traditionally endemic areas.