Q fever is an infectious disease that is spread by domestic and wild animals and ticks.

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

You can get Q fever by drinking raw (unpasteurized) milk, or after inhaling dust or droplets in the air that are contaminated with infected animal feces, blood, or birth products.

Symptoms usually develop 2 to 3 weeks after coming in contact with the bacteria. This is called the incubation period. Most people may have no symptoms; others may have moderately severe symptoms similar to the flu. 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 infected more often than women, and most people who get Q fever are between 30 and 70 years old.

This disease 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.

Common symptoms include:

• Dry cough (nonproductive)
• Fever
• Headache
• Joint pain (arthralgia)
• Muscle pains

Other symptoms that may develop include:

• Abdominal pain
• Chest pain
• Jaundice
• Rash

A physical examination may reveal crackles in the lungs or an enlarged liver and spleen. In the late stages of the disease, a heart murmur may be heard.

Tests that may be done include:

• A chest x-ray to detect pneumonia or other changes
• Blood tests to check for antibodies to Coxiella burnetti
• Liver function test
• Complete blood count (CBC)
• Tissue staining on infected tissues to identify the bacteria
• Electrocardiogram or echocardiogram to look at the heart

Treatment with antibiotics can shorten the length of the illness. Antibiotics that are commonly used include tetracycline and doxycycline. Tetracycline given by mouth should not be used by pregnant women or children who still have any baby teeth because it can permanently discolor growing teeth.

Most people get better with treatment. However, complications can be very serious and sometimes even life-threatening. Q fever should always be treated if it is recognized as the cause of symptoms.

Rarely, a heart infection results that can lead to severe symptoms or even death if untreated. Other complications can include:

• Bone infection (osteomyelitis)
• Brain infection (encephalitis)
• Liver infection (chronic hepatitis)
• Lung infection (pneumonia)

Call your health care provider if you develop symptoms of Q fever. Also call if you have been treated for Q fever and symptoms return or new symptoms develop.

Pasteurization of milk destroys the bacteria that cause early Q fever. Domestic animals should be inspected for signs of Q fever if people exposed to them have developed symptoms of the disease.

Marrie TJ, Raoult D. Coxiella burnetii (Q fever). In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 189.

Raoult D. Rickettsial infections. In: Goldman L, Schafer AI,eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 335.