Intraductal infection with H5N1 clade 2.3.4.4b influenza virus.

The ongoing outbreak of highly pathogenic avian influenza (HPAI) H5N1 of the clade 2.3.4.4b in dairy cows has led to numerous questions including how the virus transmits amongst cattle given the limited respiratory infection. One hypothesis is that the virus is spreading through fomites from udder to udder. In these studies, we demonstrate that intraductal inoculation of H5N1 but not H1N1 influenza virus results in infection in mice. This model will be useful to our understanding of the impact of influenza virus on the mammary gland, the potential as a new route of transmission, and can be used to assess if antiviral treatments prevent infections in the mammary gland.