Several distinct rickettsiae (a parasite carried by ticks, fleas, and lice) cause a disease known as typhus in humans.All cause disease with similarities of fever, headache, and rash.

由几的发疹伤寒原体（可由壁虱，蚤，虱子等寄生虫传播）引起的人们称为斑疹伤寒。