Rocky Mountain spotted fever is the most severe and most frequently reported rickettsial illness in the United States. The disease is caused by Rickettsia rickettsii, a species of bacteria that is spread to humans by ixodid (hard) ticks.

Rocky Mountain Spotted Fever Rocky Mountain spotted fever is a serious, generalized illness that is usually spread by the bite of an infected tick. Anyone who is exposed to areas where ticks live or to pets with ticks is at risk for Rocky Mountain spotted fever. Rocky Mountain spotted fever is treatable with antibiotics.

Communicable Disease Fact Sheet, Rocky Mountain spotted fever ...