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," most recent cases have been reported in the eastern United States: North and South Carolina, Virginia, Maryland, Georgia, Tennessee, and Oklahoma. Most cases occur in the spring and summer with about 1,000 cases reported per year. Most of the reported cases have been in children. The risk factors include recent hiking or exposure to ticks in an area where the disease is known to occur.
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