Q Fever (Query Fever) : Causes

Q Fever takes its origin from word “query” and is caused by bacteria Coxiella burnetii that infects some animals and is passed on to humans due to inhalation of infected air particles.

Q Fever is a worldwide zoonotic disease caused by, a bacterium called Coxiella burnetii. A zoonotic disease is an animal disease that can be transmitted to humans. Cattle, sheep, and goats are the primary reservoirs of C. burnetii. Pets (cats and dog) are common sources of infection.

Milk, birth products, urine, and faeces of infected animals contain the disease causing organisms that are resistant to heat, drying, and many common disinfectants. This resistance allow bacteria to survive for long periods in the environment. Humans are usually infected by inhalation of aerosols or infected air particles. Coxiella can be spread far through the air. Exposure to milk products is a less frequent source of infection.

Risk factors
Thirty to fifty percent of patients develop pneumonia. Hepatitis may occur in some. Majority of the people have abnormal liver function test results. Even without any treatment Q Fever resolves within several months. 1-2% people may die.

Chronic Q Fever, an uncommon entity is one that persists for more than 6 months. It is more severe. The chronic form may occur within a year after initial infection. The time lag to develop chronic disease may be as long as 20 years.

Chronic Q Fever may result in serious complications like involvement of cardiac valves (commonly the aortic valves and rarely the mitral valve), i.e. endocarditis and hepatitis.

People at risk of developing Q Fever are:

  • Those with pre-existing valvular heart disease
  • Ones with a history of vascular graft
  • Transplant recipients
  • Patients with cancer
  • Those with chronic kidney disease

Veterinary doctors, meat processing plant workers, sheep and dairy workers, livestock farmers, and researchers at facilities housing sheep are at increased risk of getting Q Fever.

Up to 65% of persons with chronic Q Fever may die of the disease. People who survive Q Fever will possess lifelong immunity against reinfection.

Q Fever compromises pregnancy. An infection during early pregnancy may lead to abortion. A later infection may cause fetal death, prematurity or at times result in an uneventful normal delivery. Patients infected during pregnancy develop chronic infection of the uterus and this leads to multiple abortions in the future.

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