Relapsing fever is a vector-borne disease caused by infection with certain bacteria in the genus Borrelia, which is transmitted through the bites of lice or soft-bodied ticks (genus Ornithodoros). Signs and symptoms
Most people who are infected develop sickness between 5 and 15 days after they are bitten. The symptoms may include a sudden fever, chills, headaches, muscle or joint aches, and nausea. A rash may also occur. These symptoms usually continue for 2 to 9 days, then disappear. This cycle may continue for several weeks if the person is not treated. Causes
Louse-borne relapsing fever
Along with Rickettsia prowazekii and Bartonella quintana, Borrelia recurrentis is one of three pathogens of which the body louse (Pediculus humanus humanus) is a vector. Louse-borne relapsing fever is more severe than the tick-borne variety.Louse-borne relapsing fever occurs in epidemics amid poor living conditions, famine and war in the developing world. It is currently prevalent in Ethiopia and Sudan.Mortality rate is 1% with treatment and 30–70% without treatment. Poor prognostic signs include severe jaundice, severe change in mental status, severe bleeding and a prolonged QT interval on ECG.Lice that feed on infected humans acquire the Borrelia organisms that then multiply in the gut of the louse. When an infected louse feeds on an uninfected human, the organism gains access when the victim crushes the louse or scratches the area where the louse is feeding. B. recurrentis infects the person via mucous membranes and then invades the bloodstream. No non-human, animal reservoir exists.
In 1873, Otto Obermeier first described the disease-causing ability and mechanisms of spirochetes, but was unable to reproduce the disease in inoculated test subjects and thereby unable to fulfill Kochs postulates. The disease was not  successfully produced in an inoculated subject until 1874. In 1904 and 1905, a series of papers outlined the cause of relapsing fever and its relationship with ticks. Both Joseph Everett Dutton and John Lancelot Todd contracted relapsing fever by performing autopsies while working in the eastern region of the Congo Free State. Dutton died there on February 27, 1905. The cause of tick-borne relapsing fever across central Africa was named Spirillum duttoni. In 1984, it was renamed Borrelia duttoni. The first time relapsing fever was described in North America was in 1915 in Jefferson County, Colorado.Sir William MacArthur suggested that relapsing fever was the cause of the yellow plague, variously called pestis flava, pestis ictericia, buidhe chonaill, or cron chonnaill, which struck early Medieval Britain and Ireland, and of epidemics which struck modern Ireland in the famine. This is consistent with the description of the symptoms experienced by King Maelgwn of Gwynedd as recorded in words attributed to Taliesin and with the "great mortality in Britain" in 548 CE noted in the Annales Cambriae. See also
Lyme disease
Typhus
Continuous fever
Intermittent fever
Remittent fever

References
External links
CDC: Relapsing Fever