The deceased - of Grays Harbor County - was an older adult with underlying health conditions, the department said in a statement released late on Friday, adding the person owned a backyard flock of mixed domestic birds.

The department found the avian flu in the flock's environment, pointing to domestic poultry or wild birds as the likely source of exposure.

It said that the risk to the general public remains low, and no other individuals involved in the case have tested positive for avian influenza, commonly called bird flu.

"Public health officials will continue to monitor anyone who was in close contact with the patient for symptoms," the department said, adding: "There is no evidence of transmission of this virus between people."

Those who had exposure to the backyard flock and its environment were also being monitored for potential symptoms, the department said.