 Rickettsiae are transmitted to through saliva injected while a tick is feeding.Unlike Lyme disease and other tick-borne pathogens that require a prolonged attachment period to establish infection, a person can become infected with "R. rickettsii" in a feeding time as short as 2 hours.In general, about 1-3% of the tick population carries "R. rickettsii", even in areas where the majority of human cases are reported.