The body louse, Pediculus humanus corporis, is infected by feeding on the blood of a patient with acute typhus fever. Patients with Brill-Zinsser disease (see Identification, above) can infect lice, and may serve as foci for new outbreaks in louse-infested communities. Infected lice excrete rickettsiae in their feces, and usually defecate at the time of feeding. People are infected by rubbing feces or crushed lice into the bite or into superficial abrasions. Inhalation of infective louse feces in dust may account for some infections. Transmission from the flying squirrel is presumed to be through the bite of the squirrel flea, but this has not been documented.