by Scholten A


Colorado tick fever is a rare viral infection from a tick bite. For most, the infection is mild. Rarely, it can affect the nervous system.


Colorado tick fever is caused by the Colorado tick fever virus. People can get the virus from the bite of an infected tick. From there, the virus gets into the blood.

The virus is not passed from person to person. In rare cases, it has been passed from a transfusion of infected blood.

Tick Bite
Bug bites
Colorado tick fever is transmitted through the bite of an infected tick.
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Risk Factors

Colorado tick fever is found in the Rocky Mountains of North America. It is also found in the western U.S and parts of Canada. The risk of getting the virus is highest for those who live in or travel to these regions, especially:

  • In mountain forest areas with heights of 4,000 to 10,000 feet
  • Between April and July


Symptoms usually appear 3 to 5 days after a tick bite. They may last for 3 weeks.

Symptoms of Colorado tick fever may be:

  • High fever and chills
  • Severe headache
  • Eye redness, sensitivity to light, or pain behind the eyes
  • Muscle pain
  • Feeling tired or weak
  • Nausea, vomiting, or diarrhea
  • Rash


The doctor will ask about your symptoms and health history. A physical exam will be done. Blood tests may be done to detect the virus and look for other problems.


There is no specific treatment for Colorado tick fever. Most people recover in 1 week. The goal is to ease symptoms. Options are:

  • Pain medicines, such as acetaminophen—to ease pain and fever
  • Fluids—to stay hydrated

Serious problems are very rare. They may include aseptic meningitis, encephalitis, and hemorrhagic fever. Severe symptoms or problems need hospital care.


To reduce the risk of Colorado tick fever:

  • Avoid tick-infested areas.
  • Wear light-colored clothing, and pants tucked into socks.
  • Use tick repellents.
  • Check for ticks often and remove them properly.
  • Wash tick bites with soap and water.


Centers for Disease Control and Prevention 

National Institute of Allergy and Infectious Diseases 


Alberta Health 

Health Canada 


Colorado tick fever. EBSCO DynaMed website. Available at: Accessed March 31, 2021.

Eickhoff C, Blaylock J. Tickborne diseases other than Lyme in the United States. Cleve Clin J Med. 2017;84(7):555-567.

Tick avoidance and removal. EBSCO DynaMed website. Available at: . Accessed March 31, 2021.

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