Definition
Q fever is an infectious disease acquired from animals, caused by the bacterium Coxiella burnetii.

Causes, incidence, and risk factors

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. If found in children younger than 3 years old, Q fever is usually during evaluation to discover the cause of pneumonia.

Prevention

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.

Symptoms
Common symptoms include:

Fever
Headache
Muscle pains
Joint pain (arthralgia)
Dry cough (non-productive)
Other symptoms that may develop include:
Chest pain
Abdominal pain
Jaundice
Rash

Signs and tests

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 can be done on the 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.