This is a rather rare bacterial disease that is spread by ticks in the United States. The incubation period varies from three to twelve days, but is usu'ally around eight days. Relapsing fever is so named because it is characterized by short periods of fever lasting two to four days alternating with periods of three to ten days withou

t fever. There are usually only a few of the febrile periods but ten or more relapses can occur. The total duration of the disease is about two weeks.

 

Antibiotics are effective. The death rate is usually between 2 and 10 percent, but may be as high as 50 percent during epi­demics.