OLYMPIA, Wash. (AP) - A warning has been issued to the public that some recently purchased cockatiels or other pet birds may pose a health risk to people who are exposed to them.

The Washington State Department of Health said Friday that some birds shipped by a national wholesale distributor tested positive for avian chlamydiosis. Health officials say about 20 PetSmart stories in 11 counties in the state have received birds from the vendor.

Officials say the pet store chain has voluntarily removed all birds supplied by the vendor and is treating its sick and exposed birds with antibiotics.

The department says there have been no reports so far of people in the state contracting the human form of the disease, called psittacosis.

The bacterium can be passed from birds to people when dust from dried bird droppings or respiratory secretions are inhaled. Symptoms of infection - usually about 5 to 19 days after exposure - may include fever, chills, headache, muscle aches and cough.