Louse-borne relapsing fever (RF) is caused by spiral-shaped bacteria called Borrelia recurrentis. RF is common in Ethiopia, Sudan and Rwanda. It is one of the epidemic-prone diseases that can cause small- or large-scale epidemics anywhere in Ethiopia, with an estimated 10,000 cases annually. RF is more common in the highlands, where it occurs mainly in the rainy seasons, but in south west Ethiopia it occurs in dry and rainy seasons equally. Epidemics of RF are often associated with epidemics of typhus, since both are transmitted by the body louse in similar conditions of overcrowding and lack of hygiene.