Definition:

Relapsing fever is a bacterial infectious disease caused by spirochaetes belonging to the genus Borrelia and is transmitted by ticks or lice. Louse-borne relapsing fever is now geographically limited, but tick-borne relapsing fever still causes major health problems in Africa. The symptoms are variable. Although relapsing fever is considered a transient disease, it persists as a residual infection in the brain, which can be reactivated on immunosuppression.