Abstract
High pathogenicity avian influenza virus H5N1 subtype (H5N1 HPAIV), clade 2.3.4.4b, is expanding its host and geographical range, and invaded Antarctica in 2023. Although mortality in Antarctic wildlife from H5N1 HPAIV has been suspected, mainly based on virological analysis of swabs collected from dead animals, it has not been unequivocally diagnosed. Here we show that H5N1 HPAIV caused high mortality in a breeding colony of skuas at one of ten sites in Antarctica we visited in March 2024. By combined virological, bacteriological and pathological analyses, we found that H5N1 HPAIV caused multi-organ necrosis and rapid death in skuas, but not in other species examined. Taken together with recent data, skuas in Antarctica are at risk of continued mortality from H5N1 HPAIV infection, threatening their already small populations. Conversely, because of their wide distribution and ecological relevance, skuas may play a substantial role in the spread of the virus across Antarctica. Transdisciplinary surveillance is needed in coming years to monitor the impact of this poultry-origin disease on Antarctica’s unique wildlife.
Data availability
A reference sequence including the multi-basic cleavage site (MBCS), generated in this study, is available in GenBank under accession number PV570239.
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Acknowledgments
We thank Ron Fouchier for support in setting up the molecular analyses, Timm Harder and Sanne Thewessen for optimizing the HPAI RT-qPCR protocol, Anne van der Linden for support with the serological analyses, Dirk Höper, Patrick Zitzow, Lukas Wessler and Kristin Trippler for support with the analyses of environmental fecal samples, Jurriaan de Steenwinkel for providing a P. multocida positive control, Micaela Carrillo, Diego Torres and Nadia Haidr for field monitoring of the breeding population of skuas at Esperanza/Hope Bay.
Funding
The HPAI Australis Expedition was funded by the International Association of Antarctica Tour Operators (IAATO) and Ocean Expeditions. MI, AG, LB, TMB, BBM, LL, PvR, MB, TK were funded by the European Union under grant agreement 101084171 (Kappa-Flu). Views and opinions expressed are, however, those of the authors only and do not necessarily reflect those of the European Union or REA. Neither the European Union nor the granting authority can be held responsible for them. The participation of BA and AA to the expedition was funded by Consejo Superior de Investigaciones Científicas (CSIC) under grant agreement 202320E224 and CSIC PTI Salud Global (Next Generation EU).
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Conceptualization: MI, AG, LB, BA, FS, MD, AA, MB, RETV, TK Methodology: MI, AG, LB, TMB, BBM, LL, PVR Investigation: MI, AG, LB, BA, MVF, BF, AEI, MBM, SL, FS, MD, AA, RETV, TK Visualization: MI, AG, LB, RETV, TK Writing – original draft: MI, AG, LB, RETV, TK Writing – review & editing: all authors.
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Iervolino, M., Günther, A., Begeman, L. et al. The expanding H5N1 avian influenza panzootic causes high mortality of skuas in Antarctica. Sci Rep (2026). https://doi.org/10.1038/s41598-025-34736-3
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DOI: https://doi.org/10.1038/s41598-025-34736-3
