Relapsing fever is caused by bacteria of certain Borrelia species and is spread by infected ticks or lice.
Other species of Borrelia cause Lyme disease.
Tick-borne relapsing fevers occur in the Americas, Africa, Asia, and Europe. In the United States, the disease occurs mainly in the Western states, particularly between May and September. Campers may be bitten by infected ticks that are usually carried by rats. However, because the ticks feed at night and do not remain attached for very long, people often do not recall a tick bite.
Louse-borne relapsing fevers are rare in the United States and occur mainly in the highlands of Central and East Africa and the Andes of South America. Louse-borne relapsing fever tends to occur in epidemics, particularly in regions affected by war, and in refugee camps. The louse infestation is usually obvious.
People have sudden chills followed by a high fever, severe headache, vomiting, and muscle and joint pain. Some people have a reddish rash on the trunk and limbs and red eyes, or they become delirious. After about 5 days, fever stops suddenly, and people feel better. However, the fever and usually the other symptoms return (relapse) and resolve at 1- to 2-week intervals for 2 to 10 episodes. The episodes become progressively less severe, and people eventually recover as they develop immunity to the disease.
Later in the illness, other symptoms may develop. They include jaundice (a yellowish discoloration of the skin and whites of the eyes), an enlarged liver and spleen, and an irregular heart rhythm or heart failure. Pregnant women may miscarry.
Antibiotics such as tetracycline, doxycycline, or erythromycin are usually effective.
Within 2 hours after the first dose of the antibiotic, an uncomfortable reaction (Jarisch-Herxheimer reaction) may occur, causing sweating, shaking chills, fever, and a fall in blood pressure. To reduce the severity of this reaction, doctors may give people acetaminophen before and after the first dose of the antibiotic.