Rocky Mountain spotted fever (RMSF) is a severe disease. It is potentially fatal. The disease is spread by ticks. It was first recognized in the Rocky Mountain states. RMSF is now found in practically all states in the US.


RMSF is caused by the bacterium Rickettsia rickettsii . It is carried by the American dog tick and the Rocky Mountain wood tick. When an infected tick bites a human, the disease is passed through the skin into the bloodstream.

The bacteria multiply inside cells of the inner lining of small arteries. This causes inflammation. The inflammation is known as vasculitis.

Risk Factors

Factors that increase your chance of RMSF include:

  • Sex: male
  • Age: children and young adults
  • Exposure to tick-infested areas
  • Contact with pets that roam in tick-infested areas
  • Being outdoors often during the months of April to September
  • Residence in or visits to states where RMSF occurs most commonly; these include, but are not limited, to:
    • Arkansas
    • Georgia
    • Kentucky
    • North and South Carolina
    • Oklahoma
    • Tennessee
    • Virginia


The first symptom of RMSF is a sudden high fever. It often occurs within 1-14 days after a tick bite. Other symptoms may include:

  • Nausea
  • Vomiting
  • Muscle pain
  • Lack of appetite
  • Severe headache

Later signs may include:

  • Rash
  • Abdominal pain
  • Joint pain
  • Diarrhea
  • Cough
  • Irritability
  • Insomnia
  • Lethargy
  • Confusion
  • Delirium or, in severe cases, coma
  • Enlarged liver, spleen, and lymph nodes
  • In severe cases, low blood pressure or shock

Immune System Including Spleen and Lymph Nodes

Immune system
© 2009 Nucleus Medical Art, Inc.


The doctor will ask about your symptoms and medical history. A physical exam will be done. RMSF can be difficult to diagnose. It can resemble other diseases. Three indicators that your doctor will look for are:

  • Fever
  • Rash (may not be present early)
  • History of a tick bite (sometimes you may not have noticed)

Blood tests may be done to confirm the diagnosis. Treatment is often started based on a best guess basis. Sometimes doctors forget to think of RMSF when adults or children have only high fever.

Especially if you have been outdoors around ticks, ask your doctor:

  • “Could I (or my child) have Rocky Mountain spotted fever?"
That simple question may save a life.


RMSF is treated with antibiotics. It is important to start this treatment early. The most commonly used antibiotics are:


The best way to prevent RMSF is to limit your exposure to ticks. If you live in an area that is prone to ticks, take the following precautions:

  • Wear light-colored clothing. This makes ticks are more visible.
  • Tuck pant legs inside socks. This stops ticks from crawling up under your pants.
  • Apply insect repellents containing DEET (applied to exposed skin). Apply permethrin to clothing.
    • For young children, DEET should be avoided or used sparingly. Carefully follow the directions on the label.
  • Carefully check your entire body for ticks after returning from outdoor areas.
  • Check pets for ticks.