The outbreak hit California dairy farms in the late summer, and shortly thereafter, some dairy workers handling the raw milk began to fall ill with avian influenza themselves. Today in the state, more than 400 dairy farms are suffering outbreaks of avian influenza.

Last Sunday, Fresno-based Raw Farm voluntarily recalled a first batch of cream top whole raw milk with a "best by" date of November 27. By Wednesday, the California Department of Public Health announced that a second batch of Raw Farm cream top, with a "best by" date of December 7 had also tested positive for bird flu, based on retail sampling.

California health officials have issued a warning against drinking a second lot of raw milk due to the bird flu virus.