CAUSED BY THE bacterium Coxiella burnetii, Q fever is an infection that can damage the lungs, liver, heart, and other vital organs. Cattle, sheep, and goats are the primary carriers of C. burnetii, which is shed in their birth products, feces, urine, and milk.1 Humans usually become infected by inhaling barnyard dust.2 Less commonly, someone becomes infected after drinking large amounts of unpasteurized milk or being bitten by an infected wood tick.3
Farmers, sheep and dairy workers, and veterinarians are at highest risk for contracting Q fever.1 However, Q fever is being reported in U.S. military personnel and civilian contractors deployed to Iraq.4
Q fever became a reportable disease in the United States in 1999, when the annual incidence was 21 cases/year. From 2000 to 2004, the incidence rose to 51 cases. Because of increasing reports in military personnel and an ongoing outbreak in the Netherlands, the CDC issued a health advisory in May 2010 warning of the potential for Q fever among travelers returning from these countries. They advise healthcare providers to evaluate travelers to and from Iraq and the Netherlands for Q fever if they present with febrile illness, pneumonia, or hepatitis.4 Because C. burnetii is highly infectious and resistant to heat and drying, it's considered a potential terrorist threat.2
Signs and symptoms
Only about half of the people infected with C. burnetii show signs and symptoms of clinical illness.3 Symptomatic patients typically experience the sudden onset of fever and other flu-like signs and symptoms about 20 days after exposure to the bacterium.1 (See Could it be Q?) Fever lasts for 1 to 2 weeks. Thirty to 50% of patients develop pneumonia, and some develop hepatitis.2
Chronic Q fever, which lasts for more than 6 months, can develop from 1 to 20 years after initial infection.2 Although uncommon, it can lead to more serious complications, including endocarditis; most patients with chronic Q fever have preexisting valvular heart disease or have had a vascular graft.
Other possible complications of Q fever include meningitis; encephalitis; cirrhosis and other liver problems; pericarditis; myocarditis; pneumonia; interstitial pulmonary fibrosis; acute respiratory distress; and miscarriage, premature birth, low birth weight, intrauterine growth retardation, and stillbirth.1,3
Diagnosis and treatment
Q fever is diagnosed based on the patient's history and clinical presentation. Obtain a careful health history of patients who present with influenza-like signs and symptoms to determine whether they have any risk factors for Q fever. Ask about their occupation and recent travel and whether they've been in contact with barnyard animals. The diagnosis of Q fever is confirmed by the detection of antibodies using complement fixation; enzyme-linked immunosorbent assay; or indirect immunofluorescence, which is the preferred method.4
Mild or asymptomatic acute Q fever often resolves within 2 weeks without treatment.3 Only 1% to 2% of patients with acute Q fever die of the infection.2 Doxycycline is the treatment of choice for adults with acute Q fever and is most effective when given within the first 3 days of illness and continued for 14 to 21 days. Fluoroquinolones such as ofloxacin and pefloxacin are alternatives. Currently, no reliable treatment is available for children under age 8 or pregnant women.4
Chronic Q fever is harder to treat, requiring the use of multiple drugs for a longer period. Two protocols currently in use for patients with Q fever endocarditis are doxycycline combined with quinolones for at least 4 years, and doxycycline combined with hydroxychloroquine for 18 months to 2 years. Some patients may also need valve replacement surgery. Sixty-five percent of patients with chronic Q fever may die of the infection.2
A vaccine for Q fever has been developed in Australia, but it hasn't been approved by the FDA for use in the United States. To prevent disease spread, the CDC recommends the following precautions for people who work in veterinary settings, meat processing plants, livestock farms, and research facilities that house sheep.
- Appropriately dispose of animal birth products.
- Restrict access to barns and labs.
- Use only pasteurized milk and milk products.
- Use appropriate procedures for bagging, autoclaving, and washing lab clothes.
- Keep holding pens for sheep away from populated areas.
- Routinely test animals for antibodies to C. burnetii. Quarantine imported animals.2
Because Q fever mimics influenza, taking a careful history of patients who present with influenza-like signs and symptoms can help you determine whether Q fever could be the cause of their illness.
1. U.S. National Library of Medicine/National Institutes of Health. Q fever
2. Centers for Disease Control and Prevention. Q fever
3. Mayo Clinic. Q fever
4. Lacasse A, Cleveland KO, Polenakovik H, Ruest A, Sinave CP. Q fever