H5N1 Bird Flu continues to take its toll in the United States

Clade 2.3.4.4b of the highly pathogenic avian influenza (HPAI) virus causing outbreaks in wild and domestic birds around the world, continues to spread in dairy cows, poultry and other animals across the United States.  Since April, the U.S. CDC confirmed 61 human cases through genome sequence analysis. In three of these cases, the amino acid substitution NA-S247N was identified that may slightly reduce susceptibility to the neuraminidase inhibitor oseltamivir in laboratory tests. The CDC also identified a different change in the polymerase acidic (PA) protein of a virus collected from a recently confirmed human case of H5N1 bird flu in California.