Rocky Mountain spotted fever

Alternative names:

spotted fever

Definition:

An infectious disease transmitted to humans by the bite of ticks.

Causes, incidence, and risk factors:

In the western U.S., the causative agent R rickettsii is transmitted by the wood tick, and in the eastern U.S., by the dog tick. Other ticks transmit the infection in the southern U.S. and in Central and South America.

Contrary to the name "Rocky Mountain" two-thirds of recent cases have been reported in the eastern United States: North and South Carolina, Virginia, Maryland, Georgia, Tennessee, and Oklahoma. The incidence of infection is 8 out of 100,000 people. Most cases occur in the spring and summer with about 1,000 cases reported per year. About 2/3 of the reported cases have been in children.

The incubation period of the illness is from 2 to 14 days after the tick bite. Symptoms usually start suddenly with a persistent fever. A rash will appear 2 to 5 days after the onset of the fever.

The risk factors include recent hiking or exposure to ticks in an endemic area.