Highly pathogenic H5N1 avian influenza viruses are becoming increasingly flexible and are adapting to mammals in new ways that could have global consequences for humans, wildlife and livestock, according to a new study of a massive outbreak among elephant seals in Argentina in 2023.
The study, published as a preprint and co-led by University of California, Davis’ School of Veterinary Medicine and the National Institute of Agricultural Technology (INTA) in Argentina, shows clear mammal-to-mammal transmission of the virus. It states the outbreak is the first known, multinational transmission of the virus in mammals ever observed globally, with the same virus appearing in several pinniped species across different countries over a short period of time.
The study’s genomic analysis showed the virus is now evolving into separate avian and marine mammal clades in South America, which is unprecedented. There is growing concern that H5N1 viruses adapted to mammal transmission could jump to other species, including people.