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. Rarely, the disease is
tick-borne. 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 pathogenic parasite.