The U.S. Centers for Disease Control and Prevention on Thursday confirmed two of the four presumptive positive bird flu cases among poultry farm workers in Washington state. The agency also ruled out bird flu infections among healthcare workers who tended to a person who contracted the virus in Missouri,

Federal health authorities have confirmed at least two people in Washington have contracted bird flu after working around poultry with the virus at a commercial egg farm in Franklin County. State and local health officials on Sunday revealed four people in Washington were “presumptively” positive for the illness,

Four agricultural workers in Washington state have tested positive for bird flu, the first human cases of H5N1 virus to be reported in the state. Washington is the sixth state to report a human infection of avian flu.