A man with chills, fever, and headache is thought to have "atypical" pneumonia. History reveals that he raises chickens and that approximately 3 weeks ago he lost many them to an undiagnosed disease. The most likely diagnosis of this man's condition is

Ornithosis (psittacosis) is caused by Chlamydia psittaci. Humans usually contract the disease from infected birds kept as pets or from infected poultry, including poultry in dressing plants. Although ornithosis may be asymptomatic in humans, severe pneumonia can develop. The disease is cured easily with tetracycline