Relapsing fever is an infection caused by several species of bacteria in the Borrelia family.
There are 2 major forms of relapsing fever:
- Tick-borne relapsing fever (TBRF) is transmitted by the Ornithodoros tick. It occurs in Africa, Spain, Saudi Arabia, Asia, and certain areas in the western United States and Canada. The bacteria species associated with TBRF are Borrelia duttoni, Borrelia hermsii, and Borrelia parkerii.
- Louse-borne relapsing fever (LBRF) is transmitted by body lice. It is most common in Asia, Africa, and Central and South America. The bacteria species associated with LBRF is Borrelia recurrentis.
Sudden fever occurs within 2 weeks of infection.
- In TRBF, multiple episodes of fever occur, and each may last up to 3 days. People may not have a fever for up to 2 weeks, and then it returns.
- In LBRF, the fever usually lasts 3 to 6 days. It is often followed by a single, milder episode of fever.
In both forms, the fever episode may end in "crisis." This consists of shaking chills, followed by intense sweating, falling body temperature, and low blood pressure. This stage may result in death.
In the United States, TBRF often occurs west of the Mississippi River, particularly in the mountains of the West and the high deserts and plains of the Southwest. In the mountains of California, Utah, Arizona, New Mexico, Colorado, Oregon, and Washington, infections are usually caused by Borrelia hermsii and are often picked up in cabins in forests. The risk may now extend into the southeastern United States.
LBRF is mainly a disease of the developing world. It is currently seen in Ethiopia and Sudan. Famine, war, and the movement of refugee groups often results in LBRF epidemics.