Q fever--California, Georgia, Pennsylvania, and Tennessee, 2000-2001.

Q fever is a zoonotic disease caused by the bacterium Coxiella burnetii. The most common reservoirs are domesticated ruminants, primarily cattle, sheep, and goats. Humans acquire Q fever typically by inhaling aerosols or contaminated dusts derived from infected animals or animal products. Its highly infectious nature and aerosol route of transmission make C. burnetii a possible agent of bioterrorism. Although up to 60% of initial infections are asymptomatic, acute disease can manifest as a relatively mild, self-limited febrile illness, or more moderately severe disease characterized by hepatitis or pneumonia. It manifests less commonly as myocarditis, pericarditis, and meningoencephalitis. Chronic Q fever occurs in <1% of infected patients, months or years after initial infection. Chronic disease manifests most commonly as a culture-negative endocarditis in patients with valvular heart disease. During 2000-2001, a total of 48 patients who met the case definition of Q fever were reported to CDC. This report describes the case investigations for six of these patients, which indicate that these persons acquired Q fever probably through direct or indirect contact with livestock. To enhance surveillance efforts, health-care providers should report cases of Q fever to state health departments.