Evidence of Rickettsia prowazekii infections in the United States.

From January 1976 through January 1979 serum specimens from 1,575 individuals were received at the Center for Disease Control and tested for antibodies to rickettsiae. Of these, sera from eight persons gave serological results indicative of recent infections with epidemic typhus rickettsiae (Rickettsia prowazekii). Five of the persons were from Georgia, and one each was from Tennessee, Pennsylvania and Massachusetts. The illnesses occurred during the winter, chiefly in persons living in a rural environment. The clinical picture was compatible with louse-borne epidemic typhus. There was no apparent contact with human body or head lice, and no cases occurred in patient contacts, indicating that infection was not associated with the classic man-louse-man cycle of epidemic typhus. Two of the eight patients had contact with flying squirrels suggesting that they became infected from this known extrahuman reservoir of R. prowazekii.