Exposure Without Active Infection: Surveillance of Influenza A Viruses and Coronaviruses in Antarctic Seabirds

Understanding the circulation of influenza A viruses and other respiratory pathogens in Antarctic wildlife is essential for anticipating outbreaks and evaluating potential impacts on vulnerable populations. During the austral summer of December 2024 and January 2025, we conducted viral surveillance in six bird species breeding at Lions Rump, King George Island, South Shetland Islands, Antarctica. A total of 199 individuals were sampled, including <i>Pygoscelis papua</i> (gentoo penguin; <i>n</i> = 81), <i>Pygoscelis adeliae</i> (Adélie penguin; <i>n</i> = 79), <i>Pygoscelis antarcticus</i> (chinstrap penguin; <i>n</i> = 34), <i>Stercorarius antarcticus</i> (brown skua; <i>n</i> = 2), <i>Chionis albus</i> (snowy sheathbill; <i>n</i> = 2), and <i>Eudyptes chrysolophus</i> (macaroni penguin; <i>n</i> = 1). All cloacal and oropharyngeal swabs tested negative for influenza A viruses and coronaviruses by RT-PCR. Blood samples from 177 birds were screened by enzyme-linked immunosorbent assay, which detected influenza A virus antibodies in 20 individuals (11.3%). Hemagglutination inhibition assays identified subtypes H6 and H11 in two penguins and H1, H5, H6, and H9 in one skua. These findings reveal no evidence of active viral infection during the sampling period but provide serological evidence of past exposure in seabird populations at Lions Rump. Continued surveillance is essential to characterize viral dynamics in Antarctic ecosystems and to support early detection and preparedness for potential incursions of emerging high-pathogenicity influenza A viruses.