Q fever is caused by Coxiella burnetii, an organism that lives in domestic animals such as cattle, sheep, goats, and cats. Some wild animals and ticks also carry the bacteria.

People get Q fever after exposure to contaminated food or raw (unpasteurized) milk, or after inhaling dust or droplets in the air which are contaminated with animal feces, blood, or birth products.

The incubation period is usually 2 to 3 weeks. The disorder may range from no symptoms to moderately severe symptoms resembling influenza. If symptoms occur, they may last for several weeks.

People at risk for infection include slaughterhouse workers, veterinarians, researchers, food processors, and sheep and cattle workers. Men are more commonly infected than women, and most patients are between 30 and 70 years old.

This disorder is occasionally seen in children, especially those who live on a farm. In infected children younger than 3 years old, Q fever is usually discovered during a search for the cause of pneumonia.

• Fever
• Headache
• Muscle pains
• Joint pain (arthralgia)
• Dry cough (non-productive)

• Chest pain
• Abdominal pain
• Jaundice
• Rash

• Physical examination may reveal crackles in the lungs and an enlarged liver and spleen.
• Liver function tests may show hepatitis.
• Low blood counts can develop.
• Antibodies for coxiella are sometimes found in the blood.
• Special stains may be done on infected tissues to identify the bacteria.
• A chest x-ray often shows pneumonia or other changes.
• Tests may be performed to determine if the disease has affected the heart.

• Relapse of infection -- see Q fever (late)
• Endocarditis (infection of heart valves)
• Chronic hepatitis (liver infection)
• Encephalitis (brain infection)
• Osteomyelitis (bone infection)
• Pneumonia (lung infection)

Pasteurization of milk and adequate cooking of food destroys coxiella bacteria.

Domestic animals should be inspected for signs of the disease if people exposed to them have developed symptoms of Q fever.