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.

Washington state health officials are investigating after four agricultural workers tested presumptively positive for bird flu, marking the first presumed human cases in the state, the Washington State Department of Health announced Sunday.

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.