Relapsing Fever


Cases of tickborne relapsing fever—United States, 1990-2011*

There are a variety of spirochete species that may cause tick-borne relapsing fever, which are most commonly transmitted by soft-bodied ticks, Ornithodoros. Transmission can also be due to lice, transmitted from human to human by the body louse. This typically occurs during times of human crisis such as war, poverty, or overcrowding. Tick-borne relapsing fever is primarily found in Africa, Central Asia, the Mediterranean, and Central and South America with only 483 cases reported in the United States.

Signs and Symptoms

Symptoms arise abruptly, presenting with a high fever as well as rapid breathing and fast heart rate, then transitioning to decreased body temperature and sweating. This cycle comes up usually a week after infection and may repeat itself multiple times. Symptoms may include headache, myalgias, arthralgias, nausea, vomiting, loss of appetite, conjunctivitis, and dry cough. More severe complications, which are less common, may include liver and spleen enlargement, meningitis, seizures, facial palsy, myocarditis, and pregnancy complications. Therefore, relapsing fever is generally more severe and acute than the more common Borrelia Burgdorferi.


A patient who presents with recurrent fevers and history of being in an endemic area should be considered for a relapsing fever diagnosis. Conventional blood tests may be helpful, but are not diagnostic. What is most helpful is dark field microscopy, enabling the visualization of spirochetes in smears of peripheral blood or cerebrospinal fluid. As the illness course goes on, diagnosis becomes more and more difficult. Untreated tick-borne relapsing fever has a death rate of five to ten percent; louse-borne relapsing fever has a death rate of close to 70 percent. However when treated, these percentages go down to around one percent.