Rocky Mountain spotted fever

Rocky Mountain spotted fever is a bacterial disease transmitted by ticks and caused by the bacterium Rickettsia rickettsii, belonging to the group of spotted fever rickettsioses ^[1]. It is primarily spread to humans through the bites of American dog ticks, Rocky Mountain wood ticks, and brown dog ticks ^[1].

The illness typically starts with fever and headache, followed a few days later by a rash composed of small bleeding spots beginning on the wrists and ankles ^[1]. Additional manifestations may include muscle pains and vomiting ^[1]. The rash often first appears two to five days after fever onset as subtle flat pink spots on wrists, forearms, and ankles, with the classic petechial rash seen in only 35–60% of patients and involving palms or soles in up to 80% ^[1].

Fewer than 5,000 cases are reported each year in the United States, usually during June and July ^[1]. The disease has been diagnosed throughout the contiguous United States, western Canada, and parts of Central and South America, and was first identified in the 1800s in the Rocky Mountains ^[1]. Approximately 0.5% of infected individuals die, whereas prior to tetracycline discovery in the 1940s fatalities exceeded 10% ^[1].

The disease is principally spread to humans by bites of American dog ticks, Rocky Mountain wood ticks, and brown dog ticks ^[1]. Rare instances of transmission through blood transfusions have been documented ^[1].

Antibiotics are not recommended for preventive use against Rocky Mountain spotted fever ^[1]. Avoidance of tick bites through exposure reduction is the implied public-health measure, given the tick-borne transmission route ^[1].

1. 1 Wikipedia contributors. Rocky Mountain spotted fever - Wikipedia [Internet]. Wikipedia. cited 23 Oct 2026. Available from: https://en.wikipedia.org/wiki/Rocky_Mountain_spotted_fever