On December 13, 2024, the CDC confirmed the first severe H5N1 bird flu case in Louisiana. This case, tied to a backyard flock, underscores a significant shift in the virus’s transmission patterns in the U.S. The patient had direct exposure to sick birds, linking the virus to backyard poultry for the first time in the country. This case is part of a broader outbreak, with 37 instances tied to dairy herds, 21 to poultry farms, and two with unknown exposure sources.

Genomic analysis of the Louisiana patient revealed the D1.1 genotype of the H5N1 bird flu virus. This genotype has been detected in recent poultry and wild bird cases in the U.S., as well as human cases in Canada and Washington. It differs from the B3.13 genotype responsible for outbreaks in poultry