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.

Washington state health officials said four agricultural workers tested presumptively positive for avian influenza, marking the first presumed human cases in the state.

Four farm workers who helped cull poultry on an commercial egg farm in Washington are presumed to have been infected with bird flu, making that state the sixth in the country to report human H5N1 infections this year.