Key points
- Q fever, caused by the bacteria Coxiella burnetii, can cause both acute and chronic illness.
- People are commonly exposed from contact with infected animals or exposure to contaminated environments.
- Symptoms usually develop within 2-3 weeks of exposure, although as many as half of infected people are asymptomatic.
Signs and Symptoms
The following symptoms are commonly seen in patients with acute Q fever. However, it is important to note that the combination of signs and symptoms vary from person to person. Some patients may not have any symptoms following infection.
- Fever
- Fatigue
- Headache
- Malaise
- Myalgia
- Chills or sweats
- Cough
- Nausea
- Vomiting
- Diarrhea
- Chest pain
Clinical assessment
Q fever is challenging for healthcare providers to diagnose and treat. The symptoms are non-specific and there is variability of presentation from patient to patient, making it difficult to distinguish from other diseases. Serology will frequently be negative in the first 2 weeks of illness. As serology is expected to be negative early in the illness course, treatment should be initiated based on clinical suspicion rather than waiting for the results of confirmatory serologic testing. Detection of Coxiella burnetii DNA by polymerase chain reaction (PCR) can rapidly confirm an acute Q fever infection. Samples are ideally taken during the first 2 weeks of illness and before or shortly following doxycycline administration. In the first 2 weeks of illness it is recommended to use serologic tests in combination with PCR of whole blood or serum. Treatment should be initiated as soon as Q fever is suspected and should not be withheld pending diagnostic test results.
Patient history. Information such as recent travel to rural or agricultural communities where infected livestock may be present, or employment in high-risk occupations, such as veterinarians or farmers, can be helpful in making the diagnosis.
Chronic Q fever is a risk for anyone with a history of acute Q fever, but the risk is greater in persons with valvular heart disease, blood vessel abnormalities, immunosuppressed persons, and people who were pregnant when they became infected. Persons with these risk factors should be routinely monitored using serologic methods every 3-6 months for the 2 years following diagnosis of acute Q fever to monitor for the development of chronic Q fever.
Other clinical evidence. Healthcare providers should also look at routine blood tests, such as a complete blood cell count and a comprehensive metabolic profile. Findings such as a prolonged fever with low platelet count, normal leukocyte count, and elevated liver enzymes suggest acute Q fever infection, but these findings may not be present in all patients. After a suspect diagnosis is made based on clinical suspicion and treatment has begun, specialized laboratory testing, including serology, should be used to confirm the diagnosis of Q fever.
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Complications
Most people with acute Q fever infection recover completely; however, some may experience serious illness with pneumonia, granulomatous hepatitis, myocarditis, or central nervous system complications.
Pregnant people who are infected (even without clinical illness) may be at risk for miscarriage, stillbirth, pre-term delivery, or low infant birth weight.
Chronic Q fever occurs in <5% of patients infected with Coxiella burnetii. It may present within weeks after an acute infection or may manifest many years later. Anyone who was infected with Coxiella burnetii is at risk for developing chronic Q fever; however, people with a history of valvular heart defects, arterial aneurysms, or vascular grafts are at increased risk. People infected by Coxiella burnetii during pregnancy and those with immunosuppression are also at increased risk of developing chronic Q fever.
Endocarditis is the most commonly identified manifestation of chronic Q fever and is fatal if untreated. Patients with endocarditis require long-term antibiotic treatment (at least 18 months) for a successful outcome. Other forms of chronic Q fever include infections of bone, liver, vascular aneurysms, or reproductive organs.