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 CDC is deploying a team to Washington state to assess the health of farm workers who culled poultry suffering from bird flu after four workers are presumed to have been infected by the virus, U.S.

Health officials are investigating the first presumed human cases of bird flu in Washington state after four agricultural workers tested positive for H5N1 last week. Why it matters: These are Washington's first presumed human cases of avian flu,

The worker are the first presumed human cases of the H5 bird flu virus under investigation in Washington state, the Washington state Department of Health said Sunday. The workers have had mild symptoms and have been offered antiviral medication by the Benton Franklin Health District.

Four agricultural workers tested “presumptively positive” for avian influenza, or bird flu, after working with infected poultry at a commercial egg farm in Franklin County, according to the Washington State Department of Health.

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.