Q fever is a worldwide disease caused by the bacteria Coxiella burnetii.
Although a variety of animal species may be infected, cattle, sheep, and goats are the primary reservoirs. Milk, urine, and feces of infected animals secrete the bacterial organisms.
This particular organism is very hardy and resistant to heat, drying, and many disinfectants. This resistance allows 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 animals.
Other modes of transmission to humans, including tick bites, ingestion of unpasteurized milk or dairy products, and human to human transmission, are rare. Humans are often very susceptible to the disease, and very few organisms may be required to cause infection.