H5N1 Bird Flu Outbreak Expands, Raising Concerns About Human Pandemic Potential

The virus has spread among dairy cattle and poultry across the U.S., with genetic mutations increasing risks to humans and animals.

H5N1 bird flu has infected over 900 dairy cattle herds in 16 U.S. states, with California declaring a state of emergency due to widespread cases.
The first U.S. human death from H5N1 was reported in January 2025, and genetic mutations in the virus are raising concerns about its potential to spread between humans.
Two distinct H5N1 subtypes are circulating: B3.13 primarily in cattle and D1.1 in poultry, with the latter linked to more severe human cases.
Researchers emphasize the need for stronger biosecurity measures, improved testing strategies for cattle, and vaccine deployment for high-risk workers.
Government response to the outbreak has been criticized as insufficient, with experts warning that prolonged circulation in mammals increases the risk of a human-adapted strain.