In the West, where herds of thousands of cattle are common, researchers are seeing cases rise at poultry and dairy operations. More than 50 workers have contracted the virus.

Infectious disease experts have called for expanded testing for H5N1 bird flu in milk since it began spreading among dairy cows in the United States this year. They argue that the virus can’t be contained until farms,

A Northern California child who consumed raw milk and became severely ill did not have the bird flu virus, according to tests conducted by the CDC.