1020 Washington St N       Twin Falls ID 83301-3156       (208) 737-5900       Toll Free: (866) 710-9775

Login or Register for the Idaho Health Alert Network

Region 5 Public Information Hotline 866-450-3594

Ebola: Information for U.S. Healthcare Workers and Settings

Mobile Website Preview

Printer Friendly    Provide Feedback

Disease Name: Q Fever

Quick Links

Please review the Idaho Reportable Disease Rules (IDAPA 16.02.10) for the most up-to-date information.

Overview / Case Definition

Q fever is a zoonotic disease caused by Coxiella burnetii, a member of the Rickettsia family of organisms. These organisms are obligate intracellular bacteria and resistant to heating, drying, and many common disinfectants; allowing the bacteria to survive for long periods of time in the environment. The infectious dose is quite low, requiring only a few organisms to cause disease. Many human infections are asymptomatic. In fact, only about 50% of infections lead to clinical illness. Symptoms are frequently non-specific, so diagnosis can be challenging. A post Q-fever fatigue syndrome has been described.

Acute Q fever

Symptoms can include high fever with rigors lasting an average of 10 days (range: 5-57 days), a severe headache, malaise, myalgia, arthralgias, confusion, sore throat, chills, night sweats, non-productive cough, nausea, vomiting, diarrhea, abdominal and chest pain; some will develop acute hepatitis or meningoencephalitis. Weight loss can occur and persist for some time. Atypical pneumonia with an abnormal radiograph has been reported in 30% to 50% of symptomatic cases. Most acute cases will recover within several months without any treatment; <5% of acute infections go on to develop chronic disease. The case fatality rate for acute Q-fever is <1%. Pregnant women may experience fetal death and abortion and have unusual serologic profiles consistent with chronic Q fever.

Chronic Q fever

This form is characterized by infection that persists for more than 6 months. Chronic Q fever can be serious. Patients who have had acute Q fever can develop the chronic form as long as 20 years after initial infection. A serious complication of chronic Q fever is endocarditis, which is often fatal. Other serious complications can include chronic hepatitis, osteomyelitis, osteoarthritis, and pneumonitis. Those with cancer, transplant recipients, chronic kidney disease, a history of heart valve defects, endocarditis, or valvular implants and those that are immunocompromised are at greatest risk for developing chronic disease and a severe disease outcome. The case fatality rate for chronic Q-fever is approximately 65%.




Within 1 working day

Reportable by Healthcare and Labs:

Reportable by Food Service Facility:

Suspect Reportable:

Reporting Timeframe: Within 1 working day

Diagnosis / Testing

Acceptable test samples include blood, sera, nasopharyngeal swabs, and bronchial washes.


C. burnetii exists in two antigenic phases called phase I and phase II. A laboratory diagnosis of Q fever requires serologic testing for antibodies against both C. burnetii phases. The naming conventions are counterintuitive, as phase II antibodies appear prior to phase 1 antibodies. Seroconversion takes 1 to 2 weeks after onset of illness. Antibodies can persist for years. Serologic evaluation of acute cases requires paired sera, collected 3-6 weeks apart, to see a rise in titers.

a. In acute cases of Q fever, the antibody level against phase II antigens are higher than those against phase I antigens, often by several orders of magnitude, and generally first detected during the second week of illness. Paired sera should ideally be collected during the first week of illness, then again 3-6 weeks later to confirm an acute illness. There should be a 4-fold change in IgG Phase II antibodies between samples. Serologic profiles of pregnant women infected with acute Q fever during gestation may progress rapidly to a serologic profile characteristic of chronic infection.

b. In chronic Q fever, the reverse situation is true with antibodies to phase I antigens of C. burnetii predominating. Phase I-specific antibodies require time to appear and indicate continued exposure to the bacteria. Thus, high levels of antibody to phase I in later specimens in combination with constant or falling levels of phase II antibodies and other signs of inflammatory disease suggest chronic Q fever. Antibodies against phase I and II antigens have been known to persist for months or years after initial infection. Serologic confirmation requires IgG against phase I antigen ≥1800 by IFA. Other tests are available.

Molecular testing

Detection of the organism by PCR in a whole blood or serum sample collected within the first two weeks after onset of illness is another test used for laboratory confirmation of an acute infection.


Diagnosis and Management of Q Fever: http://www.cdc.gov/mmwr/preview/mmwrhtml/rr6203a1.htm?s_cid=rr6203a1_w

Additional Information

Click to Call South Central Public Health District

Click to Call the Idaho State Epidemiologist

Click to Call Idaho State Communications