Investigating high pathogenicity avian influenza virus incursions to remote islands: detection of H5N1 on Gough Island in the South Atlantic Ocean

Understanding the mechanisms underlying the emergence and spread of high pathogenicity avian influenza virus(HPAIV) is critical for tracking its global dissemination, particularly via migratory seabirds, given their role intransmission over long distances. Scavenging seabirds, such as skuas, may act as both reservoirs and vectors, andhave been linked to multiple outbreaks since 2021. Here, we report the detection of HPAIV H5N1 clade 2.3.4.4b inthree Tristan skua (Stercorarius antarcticus hamiltoni) carcasses on Gough Island in the central South Atlantic Ocean.To investigate potential incursion routes, we combined genomic analyses with year-round tracking data from globallocation sensors. Although migratory movement patterns suggested southern Africa as the most obvious pathway,the strain detected on Gough Island was more closely related to that identified in South Georgia, indicating thatinfection may have occurred during the pre-laying exodus, when skuas disperse into frontal waters south of theisland. No further cases have been confirmed for Gough, but more systematic monitoring is needed to understandthe dynamics of virus infection. The detection of HPAIV H5N1 in skuas on Gough Island highlights the importance ofcontinued vigilance, proactive and geographically inclusive surveillance strategies, and biosecurity measures globally,alongside efforts to reduce other pressures on globally important seabird populations to help strengthen their resilience