The History of Epidemic Typhus

Bacteria of the order Rickettsiales were first described as short Gram-negative bacillary microorganisms that retained basic fuchsin when stained by the method of Gimenez and grew in association with eukaryotic cells (1). In 1993, the order Rickettsiales was divided into three families—namely, Rickettsiaceae, Bartonellaceae, and Anaplasmataceae. Two distinct groups are found within the Rickettsia genus, including the spotted fever group and the typhus group. In the typhus group, the two species Rickettsia typhi and Rickettsia prowazekii are pathogenic in humans (Table 1). R. typhi causes murine typhus, which is a flea-transmitted disease that occurs in warm climates (2). R. prowazekii is responsible for epidemic typhus, a disease of the cold months, during which heavy clothing and poor sanitary conditions are conducive to lice proliferation (3).