Q fever is a zoonosis caused by Coxiella burnetii. Infection with C burnetii can be acute or chronic, and exhibits a wide spectrum of clinical manifestations. The extreme infectivity of the bacterium results in large outbreaks and makes it a potential bioweapon. The clinical symptoms are those of fever, chills, severe headache, and pneumonia. The disease is usually mild, and complications are rare.
Although most persons with acute Q fever infection recover, others may experience serious illness with complications that may include pneumonia, granulomatous hepatitis (inflammation of the liver), myocarditis (inflammation of the heart tissue) and central nervous system complications. Treatment with the correct antibiotic may shorten the course of illness for acute Q fever.
On average, approximately 50-60 cases of Q fever are reported in the United States each year, and the average annual reported incidence is 0.28 cases per million persons. Data collected from Q fever case report forms submitted to CDC during 2000–2010 indicate that 320 of 405 (79%). Periodic variations were observed in monthly distribution during January 2000–December 2009; cases peaked during April–September.