Endemic typhus (murine typhus) is caused by Rickettsia typhi, a gram-negative bacteria transmitted from rodents to humans by flea bites or aerosolized flea feces.

It is found worldwide in areas with rats and the vector flea. It is grossly underestimated as a significant cause of febrile human disease in many tropical and subtropical areas. Seasonal incidence of human infections correlates with periods of abundance of vector fleas, usually summer months in the United States.

Without treatment, the mortality rate of endemic typhus is 1%-2%, most commonly in elderly patients. Many cases are subclinical and resolve without therapy.

After the flea bite, there is a 7- to 14-day incubation period. Rapid onset of flu-like illness occurs (fever in almost all cases, chills, nausea, severe headache, and myalgias) and lasts about 2 weeks. A generalized macular, papular, and/or petechial eruption develops in 50% of cases. The rash can persist for up to 10 days or fade rapidly after 2-3 days. Mental status changes (eg, confusion, delirium, stupor, apathy, nervousness, meningismus, or coma) and renal dysfunction can occur in untreated patients, but in general, endemic typhus is associated with non-severe symptoms.

A risk factor for infection is employment in a granary or brewery. Sanitation workers (garbage collectors) are at an especially high risk. Transmission occurs in domestic settings in the developing world.

There is no vaccine for endemic typhus. Person-to-person transmission has not been documented, except through the flea vector.

Cases of endemic typhus have been increasing in the United States over the past decade; most cases occur in California (primarily areas of Los Angeles and Orange counties), Texas (primarily South Texas, although new areas of endemicity have emerged), and Hawaii (primarily Maui County, with sporadic cases on all other islands).