Coxiella burnetii,
Q fever
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1-800-CDC-INFO (1-800-232-4636)
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Significance for Bioterrorism

Q fever is a zoonotic disease caused by Coxiella burnetii, a species of bacteria that is distributed globally.  In 1999, Q
fever became a notifiable disease in the United States but reporting is not required in many other countries. Because
the disease is underreported, scientists cannot reliably assess how many cases of Q fever have actually occurred
worldwide.  Many human infections are inapparent.

Cattle, sheep, and goats are the primary reservoirs of C. burnetii.  Infection has been noted in a wide variety of other
animals, including other species of livestock and in domesticated pets.  Coxiella burnetii does not usually cause clinical
disease in these animals, although abortion in goats and sheep has been linked to C. burnetii infection.  Organisms are
excreted in milk, urine, and feces of infected animals. Most importantly, during birthing the organisms are shed in high
numbers within the amniotic fluids and the placenta.  The organisms are resistant to heat, drying, and many common
disinfectants.  These features enable the bacteria to survive for long periods in the environment.  Infection of humans
usually occurs by inhalation of these organisms from air that contains airborne barnyard dust contaminated by dried
placental material, birth fluids, and excreta of infected herd animals.  Humans are often very susceptible to the disease,
and very few organisms may be required to cause infection.

Ingestion of contaminated milk, followed by regurgitation and inspiration of the contaminated food, is a less common
mode of transmission.  Other modes of transmission to humans, including tick bites and human to human transmission,
are rare.

Signs and Symptoms in Humans

Only about one-half of all people infected with C. burnetii show signs of clinical illness. Most acute cases of Q fever
begin with sudden onset of one or more of the following: high fevers (up to 104-105° F), severe headache, general
malaise, myalgia, confusion, sore throat, chills, sweats, non-productive cough, nausea, vomiting, diarrhea, abdominal
pain, and chest pain. Fever usually lasts for 1 to 2 weeks. Weight loss can occur and persist for some time. Thirty to fifty
percent of patients with a symptomatic infection will develop pneumonia. Additionally, a majority of patients have
abnormal results on liver function tests and some will develop hepatitis. In general, most patients will recover to good
health within several months without any treatment. Only 1%-2% of people with acute Q fever die of the disease.

Chronic Q fever, characterized by infection that persists for more than 6 months is uncommon but is a much more
serious disease. Patients who have had acute Q fever may develop the chronic form as soon as 1 year or as long as 20
years after initial infection. A serious complication of chronic Q fever is
endocarditis, generally involving the aortic heart
valves, less commonly the mitral valve. Most patients who develop chronic Q fever have pre-existing valvular heart
disease or have a history of vascular graft. Transplant recipients, patients with cancer, and those with chronic kidney
disease are also at risk of developing chronic Q fever. As many as 65% of persons with chronic Q fever may die of the

The incubation period for Q fever varies depending on the number of organisms that initially infect the patient. Infection
with greater numbers of organisms will result in shorter incubation periods.  Most patients become ill within 2-3 weeks
after exposure. Those who recover fully from infection may possess lifelong immunity against