Epidemic typhus in the United States associated with flying squirrels.

Between July 1977 and January 1980, seven cases of sporadic, nonepidemic "epidemic" typhus (Rickettsia prowazekii) were discovered in Virginia, West Virginia, and North Carolina. The reservoir seemed to be the southern flying squirrel (Glaucomys volans), an animal indigenous to the eastern United States; however, the vector or mode of acquisition was not evident. Diagnosis was established principally through complement fixation, indirect immunofluorescence, and toxin neutralization tests. Patients' ages were 11 to 81 years. Most were white women. Six had abrupt onset of illness. Headaches, fever, myalgias, and exanthems were among the presenting complaints. The disease seemed milder than classic louse-born epidemic typhus, but in some instances, it was life-threatening. All patients responded to tetracycline or chloramphenicol. This entity probably is more common than reported, is difficult to recognize, and is produced by an organism seemingly identical to that producing louse-born epidemic typhus.