Coxiella burnetii, the bacteria that causes Q Fever. A dry fracture of a Vero cell exposing the contents of a vacuole where Coxiella burnetii are busy growing. Q fever is a disease caused by infection with Coxiella burnetii, a bacterium that affects humans and other animals. This organism is uncommon, but may be found in cattle, sheep, goats and other domestic mammals, including cats and dogs. The infection results from inhalation of a spore-like small cell variant, and from contact with the milk, urine, feces, vaginal mucus, or semen of infected animals. The incubation period is 9-40 days. Humans are vulnerable to Q fever, and infection can result from even a few organisms. The bacterium is an obligate intracellular pathogen.