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.
Factors that increase your chance of RMSF include:
The first symptoms of RMSF often occur within 2 to 14 days after a tick bite. Symptoms may include:
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:
Immune System Including Spleen and Lymph Nodes
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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:
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.com/topics/dmp~AN~T116078/Rocky-Mountain-spotted-fever . 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