In 1938, Gordon E. Davis and Herald R. Cox identified a new rickettsial disease, which they called Nine Mile Fever, now known as Rocky Mountain Spotted fever. Rolla E. Dyer first showed the relationship of the organism to that of Australian Q Fever, and its identify was subsequently confirmed by the compliment-fixation and vaccine studies of Ida E. Bengtson.

Q fever is a zoonosis with a worldwide distribution with the exception of New Zealand. The disease is caused by Coxiella burnetii, a strictly intracellular, gram-negative bacterium. Many species of mammals, birds, and ticks are reservoirs of C. burnetii in nature. C. burnetii infection is most often latent in animals, with persistent shedding of bacteria into the environment.