Tick-borne relapsing fever in North America.

Relapsing fever is characterized by recurring episodes of fever and nonspecific symptoms (e.g., headache, myalgia, arthralgia, shaking chills, and abdominal complaints). The illness is caused by an infection from the Borrelia species (spirochetes) that may be acquired through the bite of an infected tick (Ornithodoros species) or contact with the hemolymph of an infected human body louse (Pediculus humanus). In North America, most cases have been acquired in the western United States, southern British Columbia, and few cases have been reported from Mexico. Most cases have been acquired from exposure to rustic tick-infested cabins and caves. This article reviews relapsing fever, especially tick-borne relapsing fever in North America.