Relapsing fever is an infectious disease that occurs chiefly in the tropics, often as an epidemic. It is caused by bacteria called spirochetes. A person with relapsing fever develops chills, fever, headache, and muscular aches and pains. Vomiting also may occur. These symptoms may last for several days or a week. Then the patient seems to return to good health for about a week. Suddenly, however, the symptoms return, and if the patient is not treated, he or she may have as many as 10 relapses. Doctors advise bed rest and use antibiotics.
Lice and ticks transmit the bacteria to human beings. Like typhus, louse-borne relapsing fever is found in regions with poor living conditions (see Typhus ). The two diseases often occur together. Tick-borne relapsing fever is found in the Western United States as well as in other parts of the world.