More than 250,000 poultry were euthanized in recent days in Sonoma County as the bird flu that caused egg prices to soar last winter continues to spread across California, according to various media reports.

Several California facilities were affected this fall, according to the U.S. Department of Agriculture. They include Sonoma County farms – a commercial egg layer and a duck breeder that lost 82,500 and 169,300 birds, respectively, in late November – as well as duck breeders in San Benito and Fresno counties that lost a combined 28,400 birds, also in November.

In Merced County, a turkey farm lost 31,600 birds in late October, the agency reported.

One poultry farm reportedly lost its entire operation, 170,000 ducks.

While very contagious and often fatal for birds, the highly pathogenic avian influenza does not pose a significant risk to human health, according to the California Department of Food and Agriculture, which noted the virus can be spread by migrating waterfowl.