Four agricultural workers in Washington state were recently diagnosed with avian influenza A (H5N1). The cases mark the first human infections of the disease under investigation 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.

Four new cases of bird flu were detected in farmworkers in Washington state this week. Human infections have cropping in six states as the virus spreads among farm animals.

Bird flu viruses are divided into two categories: low pathogenic avian influenza (LPAI) and highly pathogenic avian influenza (HPAI). H5N1 is an HPAI that causes severe illness an

Bird flu has possibly infected four agricultural workers in Washington state, according to the Washington State Department of Health. In a press release Sunday, the Washington State Department of Health said the “workers tested presumptively positive for avian influenza after working with infected poultry at a commercial egg farm in Franklin County.