Thousands of Adélie penguins found dead in Antarctica in 2024 were primarily victims of avian cholera, not high pathogenicity avian influenza (H5N1) as researchers initially suspected, according to a study published today in Proceedings of the Royal Society B: Biological Sciences. The findings highlight an underrecognized threat to Antarctic wildlife and the importance of comprehensive disease investigations, particularly as H5N1 continues to raise concerns for seabird and marine mammal populations.