Rocky Mountain Spotted Fever



Rocky Mountain spotted fever (RMSF) is a severe infection. It can be deadly. It is spread through the bite of a tick.

The ticks are most common in North, Central, and South America.


RMSF is caused by a specific bacteria. An infected tick can spread it through a bite.

Risk Factors

Factors that increase your chance of RMSF include:

  • Being outdoors in areas known to have RMSF especially from April to September
  • Exposure to tick-infested areas such as long grass, weeds, or low brush
  • Exposure to dogs
  • Not using preventive steps like bug spray or appropriate clothes


The first symptoms of RMSF often occur within 2 to 14 days after a tick bite. Symptoms may include:

  • Fever
  • Headache
  • Rash—begins as small, flat pink spots on wrists and ankles
  • Nausea and vomiting
  • Abdominal pain
  • Muscle or joint pain
  • Lack of appetite
  • Red eyes
  • Light hurting the eyes
  • Fatigue
  • Altered mental status
  • Severe bleeding
  • Difficulty breathing

If left untreated, RMSF can cause severe problems. Other symptoms will depend on which organs are involved.

See your doctor if you have a fever after:

  • Tick bite
  • Being in an area likely to have ticks

Immune System Including Spleen and Lymph Nodes

Immune system
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You will be asked about your symptoms and health history. A physical exam will be done. RMSF can be hard to diagnose. There are many conditions that cause similar symptoms. You may also be unaware of a tick bite. The rash may not be present yet.

The doctor may suspect RMSF based on your symptoms. A blood test may be done. They will help to find more signs of this infection.

A spinal tap may be done to look for infection around the brain.


Early treatment is important. Treatment may be started before all your tests come back.

RMSF is treated with antibiotics. Doxycycline is first choice. Make sure to take all of the medicine as advised.


Tick bites can cause a number of infections. If you are in an area that may have ticks:

  • Wear light-colored clothing. You will be better able to see ticks.
  • Tuck pant legs inside socks. This will stop ticks from crawling up under your pants.
  • Use insect repellents with DEET. Apply to exposed skin. Permethrin can be put on clothing.
    • DEET should be avoided or used sparingly for small children. Follow the directions on the label.
  • Carefully check your entire body for ticks after returning from outdoor areas.
  • Treat your pets for ticks. Check pets for ticks after being outdoors.


Centers for Disease Control and Prevention
Family Doctor—American Academy of Family Physicians


Public Health Agency of Canada
The College of Family Physicians of Canada


Rocky Mountain spotted fever. EBSCO DynaMed website. Available at: http://www.dynamed... . Accessed January 29, 2021.
Rocky Mountain spotted fever (RMSF). Centers for Disease Control and Prevention website. Available at:
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Accessed January 29, 2021.
Last reviewed March 2020 by EBSCO Medical Review Board David L. Horn, MD, FACP
Last Updated: 1/29/2021

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