A febrile illness usually accompanied by rigors, myalgia, malaise, and retrobulbar headache.
Severe disease can include acute hepatitis, pneumonia, and meningoencephalitis.
Clinical laboratory findings may include elevated liver enzyme levels and abnormal chest film findings. Asymptomatic infections may also occur. A chronic fatigue-like syndrome has been reported in some Q fever patients. I antigen in paired serum specimens ideally taken 3-6 weeks apart, or, Isolation of C. burnetii from a clinical specimen by culture, or Demonstration of C. burnetti in a clinical specimen by detection of antigen or nucleic acid. Cutoff titers are determined by individual laboratories.