Caused by R. typhi, endemic murine typhus has a rat reservoir and is transmitted by fleas.

• Humans become infected when Rickettsia-laden flea feces are scratched into pruritic bite lesions; less often, the flea bite itself transmits the organisms or aerosolized rickettsiae from flea feces are inhaled.
• In the United States, endemic typhus occurs mainly in southern Texas and southern California; globally, it occurs in warm (often coastal) areas throughout the tropics and subtropics.
• Flea bites often are not recalled by pts, but exposure to animals such as cats, opossums, raccoons, skunks, and rats is reported by ~40%.
• Risk factors for severe disease include older age, underlying disease, and treatment with a sulfonamide drug.