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Q Fever

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Reporting Obligations

All suspect and confirmed cases must be reported to the local Health Unit.

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Aetiologic Agent

Q fever is caused by Coxiella burnetii (C. burnetti), a gram-negative intracellular bacterium. C. burnetti can be found in the urine, feces and milk of infected animals, with the highest numbers of bacteria shed in birth products such as the placenta and amniotic fluid. C. burnetti is highly resistant to many disinfectants and environmental conditions. C. burnetii may be used as a bioterrorism agent.

Clinical Presentation

Approximately half of humans infected with C. burnetii do not show symptoms. Q fever can cause acute or chronic illness in humans. The acute symptoms caused by infection with C. burnetii usually develop within 2–3 weeks of exposure.

Symptoms commonly seen with acute Q fever include: fever, severe headache, general malaise, myalgia, chills/sweats, non-productive cough, nausea, vomiting, diarrhea, abdominal pain and chest pain, however, it is important to note that the combination, duration and severity of symptoms vary greatly from person-to-person. Children with Q fever generally have a milder acute illness than adults.

Although most persons with acute Q fever infection recover, others may experience serious illness with complications that include pneumonia, granulomatous hepatitis, and rarely myocarditis or central nervous system complications. Pregnant women who are infected may be at risk for pre-term delivery, miscarriage, stillbirth or low infant birth weight.

Chronic Q fever is a severe disease occurring in <5% of acutely infected patients. It may present soon (within 6 weeks) after an acute infection, or potentially manifest years or decades later. Endocarditis is the most commonly identified manifestation of chronic Q fever and is fatal if untreated, whereas with treatment the 10-year mortality rate is 19%. Other forms of chronic Q fever include aortic aneurysms and infections of vascular aneurysms, the bone, liver or reproductive organs, such as the testes in males. The three groups at highest risk for chronic Q fever are pregnant women, immunosuppressed persons and patients with pre-existing heart valve defects. Although the majority of people with acute Q fever recover completely, a post-Q fever fatigue syndrome has been reported to occur in up to 20% of patients with acute Q fever. This syndrome is characterized by constant or recurring fatigue, night sweats, severe headaches, photophobia, pain in muscles and joints, mood changes, and difficulty sleeping.

Modes of Transmission

When infected, animals shed the bacteria in urine, feces, milk and especially birth products such as placenta. Shedding of organisms may be intermittent. Transmission occurs most commonly through air-borne dissemination of C. burnetti in dust or aerosols from premises contaminated by placental tissues, birth fluids, and excreta of infected animals. Airborne particles containing organisms may be carried downwind one kilometer or more. As a result, individual cases may occur where no animal contact can be demonstrated. Infections may also occur from direct exposure to infected animals or tissues or through exposure to contaminated materials such as wool, straw, or even laundry. Raw milk from infected goats or cows contains viable organisms and may be responsible for human transmission. Person-to-person transmission is possible, though rare, through sexual transmission, transplacental transmission and by blood or marrow transfusion.

Incubation Period

Depends on the size of the infectious dose, usually 2–3 weeks for acute Q fever, with a range of 3–30 days. Chronic Q fever can develop years after an initial infection.

Period of Communicability

C.burnetti is extremely resistant to physical stresses, including heat, disinfectant chemicals and desiccation and can survive in the environment for months to years. Direct person-to-person transmission occurs rarely, although sporadic cases of nosocomial transmission during autopsies and obstetrical procedures of infected women have occurred.

Risk Factors/Susceptibility

Susceptibility is general. Persons with valvular heart disease or vascular defects, pregnant women, and persons who are immunosuppressed are at greater risk for chronic Q fever after an acute infection. Those who recover from infection may possess lifelong immunity against re-infection.

Diagnosis and Laboratory Testing

The following will constitute a confirmed case of Q fever (with onset of sudden chills, myalgia, weakness, malaise, headache and sweats):

  • Isolation of C. burnetii from a clinical specimen
  • A four-fold or higher rise in IgG antibodies to phase II antigen
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Treatment and Case Management

Treatment is under the direction of the attending health care provider (acute cases, generally require treatment with antibiotics).

Provide cases with information about the infection and how it spreads. If a source has been identified, ask the case(s) for a list of persons who may also have come in contact with the infectious item or area.

Patient Information

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Additional Resources

Ministry of Health and Long-Term Care. “Diseases – Q Fever, 2003”.

Centers for Disease Control and Prevention. “Q Fever, 2013”


Ministry of Health and Long-Term Care, Infectious Diseases Protocol, 2022.