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Disease Name: Q Fever


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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%.


Restrictions

None


Reporting

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.

Serology

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.


Treatment

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


Additional Information


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