Respiratory infection with pneumonia caused by Chlamydia psittacosi, a micro-organism that occurs in parrots, but also in parakeets, pigeons, chickens and other birds; the birds themselves are sometimes merely carriers. The disease is transmitted to human beings by inhalation of substances contained in the feathers or excrement of infected birds. In rare cases it passes from man to man by droplet inhalation. Five to fifteen days after infection there is high fever with headache and pneumonia symptoms. The disease can vary from mild to severe; it should be distinguished from other forms of pneumonia. The keeping of birds by the patient can often be a clue to the cause. Treatment is usually with the administration of tetracycline antibiotics.