Dairy industry experts say the virus entered California after local cows were shipped to another state and then returned to California.

All of the state's cases have been linked to contact with infected dairy cows, officials said. No human-to-human transmission has been documented.

However, there is urgent concern over dairy cows. In California’s Central Valley, the carcasses of dead cattle have been piling up, a phenomenon documented in videos taken by a local veterinarian. According to the CDC,

Four agricultural workers in southeast Washington have preliminarily tested positive for bird flu after working around an infected poultry flock at a commercial egg farm. The cases, if confirmed, woul