Mpox (or monkeypox) is an emerging zoonotic disease caused by the mpox virus (MPV), which has recently spread geographically, particularly with the emergence of clade Ib in Central Africa. Since December 2025, cases have been reported in the south-western Indian Ocean territories, linked to an active outbreak in Madagascar. In Mayotte Island, ten cases were confirmed between January and February 2026, including imported cases and local secondary and tertiary transmissions. In Réunion Island, four cases were identified, all associated with a stay in Madagascar or secondary transmissions. The patients mainly presented with polymorphic cutaneous and mucosal lesions, with no severe cases reported. Diagnosis is based on MPV detection and typing (clade determination) using nucleic acid amplification tests (PCR) on samples taken from lesions. Management is based on symptomatic treatment and control measures including isolation and vaccination of contacts. The introduction of clade Ib into these territories highlights the need for increased vigilance, appropriate virological surveillance and coordination between local and regional public health actors in order to prevent the spread of this virus.
