Final answer:
Rocky Mountain spotted fever is marked by a high fever, severe headache, and a petechial rash that spreads from the extremities to the trunk and is caused by the bacterium Rickettsia rickettsii transmitted through tick bites.
Step-by-step explanation:
Rocky Mountain spotted fever (RMSF) is an acute illness characterized by petechial rash, high fever, severe headache, and myalgias (muscle pain). The rash, which distinguishes RMSF, begins on the hands and wrists, and feet and ankles, before spreading to the trunk, face, and other extremities. RMSF is caused by the bacterium Rickettsia rickettsii and is transmitted by tick bites, specifically from species such as the American dog tick, Rocky Mountain wood tick, and brown dog tick.
Signs of RMSF typically occur within two weeks of the bite and can include initial symptoms like high fever and headache, soon followed by the characteristic rash. If untreated, RMSF can result in serious complications including hypotension, cardiac arrest, or ischemia due to increased vascular permeability, and can be fatal especially if treatment is not started quickly, generally before the rash appears.