Rocky Mountain spotted fever is an illness caused by a microorganism that infects humans through the bite of a tick. A severe headache, fever and rash typically appear within one week of infection. The disease gets its name from the Rocky Mountain area where it was first reported, but its occurrence is widespread in the United States; cases are most common in the southern Atlantic states.

The wood tick and dog tick are the primary carriers, and either can be found in both city and woodland locales. More than 90 percent of cases occur between April 1 and September 30—the time of year when ticks are most prevalent.

Children and adolescents account for nearly half of cases, primarily because of increased tick exposure through outdoor activity. Untreated—especially in older patients—Rocky Mountain spotted fever may result in heart failure, pneumonia, or coma, and is fatal in 20 to 30 percent of cases.

According to the National Institutes of Health (NIH) in June 2015, epidemics of Rocky Mountain spotted fever occurred on two American Indian reservations in Arizona, resulting in 300 cases of the disease and 20 deaths between 2002 and 2014. Health care agencies (federal, state, and tribal) have been working together to build effective community-based tick control/tick bite prevention programs.

What Causes Rocky Mountain Spotted Fever?

  • A bite from a tick infected with the microorganism Rickettsia rickettsii.
  • The organism invades and multiplies in cells lining the arteries and veins throughout the body, causing vasculitis.

Symptoms of Rocky Mountain Spotted Fever

  • Severe headache
  • Chills and a high fever that reaches 103°F to 104°F within the first two days.
  • A rash appears between the second and sixth day of illness. It begins at the wrists and ankles and within 24 hours spreads to the rest of the body and face. In about 10 percent of patients, the rash does not occur or is barely noticeable, particularly in males and persons with dark skin.
  • Nausea and vomiting
  • Diarrhea and abdominal pain
  • A dry cough
  • Muscle aches
  • Heightened sensitivity to light
  • Lack of appetite
  • Deep muscle pain
  • Significant tiredness
  • Mental confusion
  • Abnormal sensitivity to light
  • Excessive thirst
  • Hallucinations


  • Minimize contact with ticks and tick-infested areas.
  • Wear protective clothing and use an insect repellent with DEET on exposed skin and clothes.
  • Inspect your body several times a day for ticks when visiting a tick-infested area.
  • Check dogs for ticks; ticks may infect the animal and establish a host for further transmission.
  • Remove an attached tick with tweezers: grasp it as close to the skin as possible, being careful not to squeeze the body of the tick, which may spew infectious microorganisms into the bloodstream. Pull the tick steadily upward without twisting. Do not handle it after removal. Transmission is unlikely unless the tick has been attached for a number of hours.
  • Wash the bite area with soap and water or antiseptic to destroy any contaminants.

Diagnosis of Rocky Mountain Spotted Fever

  • A patient history should include any recent outdoor activities or travel in tick-infested areas.
  • Microscopic examination of a biopsy of skin or rash is the only way to make a conclusive diagnosis early in the disease.

How to Treat Rocky Mountain Spotted Fever

  • Antibiotic drug therapy (usually doxycycline, tetracycline or chloramphenicol) should be administered as early as possible in the course of illness. If treatment is delayed until the rash is widespread, therapy is less effective.
  • If untreated, the illness often abates after two weeks and convalescence is usually rapid.

When to Call a Doctor

  • Call a doctor when there are symptoms of rash, fever, headache and weakness, regardless of whether or not a tick bite is evident. Conclusive diagnosis and appropriate treatment are only available through a physician.


Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference

Simeon Margolis, M.D., Ph.D., Medical Editor

Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at

Published: 29 Aug 2011

Last Modified: 22 Jun 2015