Reports of cases of an acute febrile disease of unusual character were first received by the New York City Department of Health toward the end of June 1946. Sussman1reported a recent increase of cases of a peculiar " spotted fever"disease which appeared in the housing development in Kew Cardens, Queens. The clinical appearance resembled that of typhus. The failure to cause agglutination with the usual antigens distinguished the condition from known diseases. Shankman2 examined more than 60 patients presenting similar symptoms during the same period in the three block square area of Regency Park. The area involved was infested with mice and rats so that the possibility of a rickettsia or virus etiology was strongly suggested.
A joint study by the New York City Health Department and the United States Public Health Service of 144 nonfatal cases of this disease3 helped to establish the disease as a