Epidemic typhus is caused by Rickettsia prowazekii. Symptoms are prolonged high fever, intractable headache, and a maculopapular rash.
Humans are the natural reservoir for R. prowazekii, which is prevalent worldwide and transmitted by body lice when louse feces are scratched or rubbed into bite or other wounds (or sometimes the mucous membranes of the eyes or mouth). In the US, humans occasionally contract epidemic typhus after contact with flying squirrels.
Fatalities are rare in children < 10 yr, but mortality increases with age and may reach 60% in untreated patients > 50 yr.
Symptoms and Signs
After an incubation period of 7 to 14 days, fever, headache, and prostration suddenly occur. Temperature reaches 40° C in several days and remains high, with slight morning remission, for about 2 wk. Headache is generalized and intense. Small, pink macules, which appear on the 4th to 6th day, rapidly cover the body, usually in the axillae and on the upper trunk and not on the palms, soles, and face. Later, the rash becomes dark and maculopapular. In severe cases, the rash becomes petechial and hemorrhagic. Splenomegaly sometimes occurs. Hypotension occurs in most seriously ill patients. Vascular collapse, renal insufficiency, encephalitic signs, ecchymosis with gangrene, and pneumonia are poor prognostic signs.
Louse infestation is usually obvious and strongly suggests typhus if history (eg, living in or visiting an endemic area) suggests possible exposure. For details of diagnosis, see Rickettsiae and Related Organisms: Diagnosis.
Primary treatment is doxycycline 200 mg po once followed by 100 mg bid until the patient improves, has been afebrile for 24 to 48 h, and has received treatment for at least 7 days. Chloramphenicol 500 mg po or IV qid for 7 days is 2nd-line treatment.
Immunization and louse control are highly effective for prevention. However, vaccines are not available in the US. Lice may be eliminated by dusting infested people with malathion or lindane.
Brill-Zinsser disease is a recrudescence of epidemic typhus, occurring years after an initial attack.
Patients with Brill-Zinsser disease acquired epidemic typhus earlier or lived in an endemic area. Apparently, when host defenses falter, viable organisms retained in the body are activated, causing recurrent typhus; thus, disease is sporadic, occurring at any season and in the absence of infected lice. Lice that feed on patients may acquire and transmit the agent.
Symptoms and signs are almost always mild and resemble those of epidemic typhus, with similar circulatory disturbances and hepatic, renal, and CNS changes. The remittent febrile course lasts about 7 to 10 days. The rash is often evanescent or absent. Mortality is nil.
For diagnosis and treatment, see Rickettsiae and Related Organisms: Diagnosis.
Last full review/revision November 2012 by William A. Petri, Jr., MD, PhD
Content last modified December 2012