Jason Gale (@jasongale.bsky.social)

Highly pathogenic avian influenza H5N1: history, current situation, and outlook | Journal of Virology Influenza virus pandemics are caused by influenza A viruses and happen in irregular intervals (1). The H1N1 subtype caused a pandemic in 1918 that claimed between 20 and 50 million lives, followed by H2N2 in 1957 (1–4 million deaths), H3N2 in 1968 (1–4 million deaths), and another H1N1 pandemic in 2009 (approximately 280,000 deaths) (2, 3). Typically, after causing a pandemic, these viruses establish themselves in the human population and become seasonal influenza viruses. Currently, H1N1 and H3N2 (as well as influenza B viruses) are circulating as seasonal influenza viruses in humans and cause millions of severe infections and up to 650,000 deaths per year globally (4). In addition, highly pathogenic avian influenza (HPAI) of the H5N1 subtype has caused a panzootic in birds since 2021, devastating poultry production around the world as well as infecting multiple mammalian host species. An outbreak in US dairy cattle has resulted in thousands of cows infected across 16 states, with subsequent spillback to birds and spillover to other mammals. Human H5N1 infections have concurrently increased, as exposures to infected animals have become more frequent. The risk of an H5N1 influenza pandemic continues to grow. https://journals.asm.org/doi/10.1128/jvi.02209-24