Since 1970, reports of only 8 cases of Brill-Zinsser disease have been published (
9,10). In all cases, known risk factors were present (overcrowding, poor hygiene, or contact with flying squirrels). Brill and Zinsser described that stress or waning immunity could reactivate
R. prowazekii infection (
2). Corticosteroids can trigger recurrence of
R. prowazekii in mice (
2), but no such observations were made in humans. In the case presented here, we found no stress factor, no immunosuppression, and no medical history of epidemic typhus.
Brill-Zinsser disease can develop >40 years after acute infection. The mechanism of
R. prowazekiilatency has not been established.
A recently explored reservoir for silent forms of R. prowazekiiinfection is adipose tissue because it contains endothelial cells, which are the target cells for
R. prowazekii infection, and because of its wide distribution throughout the body (
2). Brill-Zinsser disease should be considered as a possible diagnosis for acute fever in any patient who has lived in an area where epidemic typhus is endemic.