Observations on the epidemiology of Q fever in Northern California.

Q fever was described as a new clinical entity by Derrick 1 in 1937. The original description was based on febrile illnesses observed among abattoir workers in Queensland, Australia, 2 and for some years the disease was recognized only in that area. Since 1944, however, the disease has been identified in Mediterranean Europe and Africa, in France, Germany, Switzerland, Rumania and England; in the Western Hemisphere, Q fever has been reported from Panama and several parts of the United States. Prior to 1946 the only authenticated instance of naturally acquired Q fever in the United States was that reported by Hesdorffer and Duffalo 3 in 1941. In 1946 there occurred two large outbreaks of Q fever among workers in meat-packing houses; one outbreak, involving 55 persons, occurred in Amarillo, Texas, 4 the other, involving 33 persons, occurred in Chicago. 5 In May 1947, Q fever was identified in California in