This type of typhus occurs when cold weather, poverty, war, and other disasters result in close living conditions which encourage the maintenance of a population of lice living among humans. Epidemic typhus is now found in the mountainous regions of Africa, South America, and Asia. Brill-Zinsser disease is a reactivation of an earlier infection with epidemic typhus. It affects people years after having completely recovered from epidemic typhus. This illness tends to be extremely mild.
Endemic typhus is carried by fleas.
When a flea lands on a human, it may defecate as it feeds. When the person scratches the itchy spot where the flea was feeding, the bacteria-laden feces are scratched into the skin, thus causing infection. The causative bacteria is called Rickettsia typhi . Endemic typhus occurs most commonly in warm, coastal regions. In the United States, southern Texas and southern California have the largest number of cases.