With the start of 2024, highly pathogenic avian flu outbreaks have already been confirmed in four states, with California the hardest-hit state, according to the latest updates from the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS).

In California, the virus was detected at three more commercial farms, including a layer pullet farm in Merced County housing more than 760,000 birds, a broiler farm in Merced County that has nearly 535,000 birds, and a broiler farm in Sonoma County that has nearly 78,000 birds. Also, officials reported an outbreak involving two of the state's backyard flocks, one in Merced County and the other in Sacramento County.

Meanwhile, two other states reported outbreaks affecting commercial farms. Wisconsin reported an event at a turkey facility in Washburn County that has 41,000 birds, and in Kansas, the virus hit a layer pullet farm in Rice County that was raising 240,000 birds. Colorado reported an outbreak in a backyard flock in Arapahoe County.

So far this year avian flu outbreaks have led to the loss of 1.66 million birds, APHIS said. The H5N1 outbreaks began in US poultry in February 2022 and have so far led to a record loss of 81.37 million birds across 47 states.