Psittacosis (parrot fever) is a rare pneumonia caused by Chlamydia psittaci, a bacterium present mainly in birds such as parrots, macaws, parakeets, and lovebirds. It is also present in other birds, such as pigeons, finches, chickens, and turkeys.

Usually, people are infected by inhaling dust from the feathers or the waste of infected birds. The organism also may be transmitted by a bite from an infected bird and, rarely, from person to person in cough droplets. Psittacosis mainly occurs in bird fanciers or in people who work in pet shops or on poultry farms.

About 1 to 3 weeks after being infected, a person develops a fever, chills, fatigue, and loss of appetite. A cough develops, which is initially dry but later brings up greenish sputum (thick or discolored mucus). Fever persists for 2 to 3 weeks and then slowly subsides. The disease may be mild or severe, depending on the person’s age and the extent of lung tissue involved.

Blood tests to determine whether the person has a certain type of antibody, suggesting recent infection with Chlamydia psittaci, are the most reliable method for confirming the diagnosis, but doctors usually suspect the infection in people who have a history of exposure to birds.