Patients exposed to Q fever by aerosol do not present a risk for secondary contamination or re-aerosolization of the organism. The endemic form of Q fever is a zoonotic disease caused by a rickettsia, Coxiella burnetii . Its natural reservoirs are sheep, cattle and goats, and grows to especially high concentrations in placental tissues. Exposure to infected animals at parturition is an important risk factor for endemic disease. The organisms are also excreted in animal milk, urine, and feces.
Humans acquire the disease by inhalation of aerosols contaminated with the organisms.
Farmers and abattoir workers are at greatest risk occupationally. A biological warfare attack with Q fever would cause a disease similar to that occurring naturally. Q fever is also a significant hazard in laboratory personnel who are working with the organism. Coxiella burnetii , the causative agent, was discovered in 1937. This organism is a rickettsial agent that is resistant to heat and desiccation and highly infectious by the aerosol route.