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Q fever

Q fever

11 August 2017

Causative agent

Q fever (Query fever) is a zoonotic infection caused by bacteria Coxiella burnetii. The bacteria is found in farm animals (especially cattle, sheep and goats), domesticated pets, some wild animals and ticks. The infection exists worldwide. Livestock handlers, dairy workers and farmers are at higher risk of contracting the disease.

Clinical features

Acute infection of Q fever may present with fever, chills, headache, muscle pain, malaise and weight loss. Severe diseases include acute hepatitis and chest infection. Asymptomatic infection may also occur.

Some people may develop a chronic form of the disease, where symptoms persist for months to years after acute infection. A serious complication of chronic Q fever is infection of heart valves (endocarditis), particularly in persons with underlying heart diseases. Transplant recipients, cancer patients, those with chronic kidney disease, weakened immunity and pregnant women are at higher risk of developing chronic Q fever.

Mode of transmission

Q fever is mainly transmitted through inhalation of particles contaminated by placental tissues, birth fluids and excreta of infected animals. It can also be spread by direct contact with infected animals and their produce, or consuming unpasteurised dairy products. Transmission via a tick bite and person-to-person transmission are rare.

Incubation period

The incubation period is usually 2 – 3 weeks.


Q fever can be treated by antibiotics, but for acute Q fever, most cases will recover without antibiotic treatment. For chronic Q fever, however, the treatment generally takes at least several months.


At present, there is no vaccine against Q fever available in Hong Kong. The public should adopt the following measures to reduce the risk of infection:

  • Avoid contact with farm animals or wild animals;
  • Observe good personal and food hygiene;
  • Dairy products should be pasteurised before consumption.