Relapsing Fever is a disease characterized by relapsing or recurring episodes of fever, often accompanied by headache, muscle and joint aches and nausea.  There are two forms of relapsing fever:

• Tick-borne relapsing fever (TBRF)

• Louse-borne relapsing fever (LBRF)

TBRF is caused by several species of spiral-shaped bacteria that are transmitted to humans through the bite of infected soft ticks.  Most cases occur in the summer months and are associated in particular with sleeping in rustic cabins in mountainous areas of the Western United States.  There are approximately 25 cases of TBRF in the United States each year.

LBRF is caused by another spiral-shaped bacteria, Borrelia recurrentis that is transmitted from human to human by the body louse.  LBRF still causes sporadic illness and outbreaks in Africa.  Illness can be severe, with mortality of 30 to 70% in outbreaks.  For more information on LBRF see Hayes and Dennis, Relapsing Fever. In Harrison's Principles of Internal Medicine. 16th edition. 2004. P991-995 or Rahlenbeck and Gebre-Yohannes 1995.