Mayo Clinic Health Library

Q fever

Updated: 07-07-2011

Definition

Q fever usually is a mild disease with flu-like symptoms. Many people have no symptoms at all. But in a small percentage of people, the infection can resurface years later. This more deadly form of Q fever can damage your heart, liver, brain and lungs.

Q fever is transmitted to humans by animals, most commonly sheep, goats and cattle. When you inhale barnyard dust particles contaminated by infected animals, you may become infected. High-risk occupations include farmers, veterinarians and people who work with sheep in research labs.

The mild form of Q fever typically clears up within a few weeks with no treatment. But if Q fever recurs, you may need to take a combination of antibiotics for at least 18 months.

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Symptoms

Many people infected with Q fever never show symptoms. If you do have symptoms, you'll notice them about two to three weeks after exposure to the bacteria. Signs and symptoms may include:

  • High fever, up to 105 F (40.5 C)
  • Severe headache
  • Fatigue
  • Cough
  • Nausea
  • Diarrhea
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Causes

Q fever is caused by a type of bacteria called Coxiella burnetii, most commonly found in sheep, goats and cattle. It also can infect pets, such as cats, dogs and rabbits.

These animals transmit the bacteria through their urine, feces, milk and birthing products — such as the placenta and amniotic fluid. When these substances dry, the bacteria in them become part of the barnyard dust that floats in the air. The infection is usually transmitted to humans through their lungs, when they inhale contaminated barnyard dust.

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Risk factors

Certain factors can increase your risk of being infected with Q fever bacteria, including:

  • Occupation. Certain occupations place you at higher risk because you're exposed to animals and animal products as part of your job. At-risk occupations include veterinary medicine, meat processing, livestock farming and animal research.
  • Location. Simply being near a farm or farming facility may put you at higher risk of Q fever, because the bacteria can travel long distances, accompanying dust particles in the air.
  • Your sex. Men are more likely to develop symptomatic acute Q fever.

Risks for chronic Q fever
The risk of eventually developing the more deadly form of Q fever is increased in people who have:

  • Heart valve disease
  • Blood vessel abnormalities
  • Weakened immune systems
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Complications

A Q fever recurrence can affect your heart, liver, lungs and brain, giving rise to serious complications, such as:

  • Endocarditis. An inflammation of the membrane surrounding your heart, endocarditis can severely damage your heart valves. Endocarditis is the most common and the most deadly of Q fever's complications.
  • Lung issues. Some people who have Q fever develop pneumonia. This can lead to acute respiratory distress, a medical emergency in which you're not getting enough oxygen.
  • Pregnancy problems. Chronic Q fever increases the risk of miscarriage, low birth weight, premature birth and stillbirth.
  • Liver damage. Some people who have Q fever develop hepatitis, an inflammation of the liver that interferes with its function.
  • Meningitis. Q fever also can cause meningitis, an inflammation of the membrane surrounding your brain and spinal cord.
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Preparing for your appointment

You might first bring your symptoms to the attention of your family doctor, but he or she might refer you to an infectious disease specialist.

What you can do
Before your appointment, you may want to write a list of answers to the following questions:

  • What are your symptoms and when did they begin?
  • Are any of your heart valves malformed?
  • Have you ever had heart surgery?

What to expect from your doctor
Your doctor may ask some of the following questions:

  • Have you been exposed to any barnyard or livestock environments recently?
  • Have you come into contact with newborn animals within the past few weeks?
  • Do you live near a large farming area?
  • Are you pregnant?
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Tests and diagnosis

To diagnose Q fever, your doctor will perform one or more blood tests, along with additional tests if chronic Q fever is suspected.

Lab tests
Your doctor may want to check your blood for antibodies to the Coxiella burnetii antigen and for evidence of liver damage.

Imaging tests

  • Chest X-ray. Q fever can cause pneumonia in some people. A chest X-ray can be used to see if your lungs look healthy.
  • Echocardiography. If chronic Q fever is suspected, your doctor may do an echocardiogram to check for problems with your heart valves.
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Treatments and drugs

Treatment for Q fever depends on the severity of your symptoms. Mild or nonsymptomatic cases of acute Q fever often get better in about two weeks with no treatment.

Medications
If you have more severe symptoms, your doctor will prescribe antibiotics. People who have chronic Q fever usually must take a combination of antibiotics for at least 18 months. Even after successful chronic Q fever treatment, you'll need to go back for follow-up tests for years in case the infection returns.

Surgery
If you have Q fever endocarditis, you may need surgery to replace damaged heart valves.

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Prevention

A Q fever vaccine is available in the United States, but a different vaccine that originated in Australia has been studied more thoroughly. You may want to consider vaccination if you're at high risk of developing Q fever complications and you work in an environment that may expose you to the disease.

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