Rocky Mountain spotted fever is a bacterial infection passed to humans by wood ticks and dog ticks that can lead to life-threatening complications, such as shock and kidney failure, if it is not treated promptly. Initial symptoms usually start about 2 to 14 days after the tick bite and may include a sudden fever, severe headache, muscle and joint aches, distinct rash, and nausea and vomiting.

The rash is usually made up of many tiny, flat, purple or red spots (petechial rash). It usually starts on the wrists and ankles, then spreads to the arms and legs and the rest of the body.

It is also called tick fever, spotted fever, or tick typhus. Rocky Mountain spotted fever is found in the southeastern, western, and south-central United States.