Colorado tick fever is an infection that is spread to humans by the bite of an infected tick.
Colorado tick fever is caused by the Colorado tick fever virus. Humans can get the virus through the bite of an infected tick. The Rocky Mountain wood tick is the main carrier of the Colorado tick virus in the United States (US). This tick can be found in the western US states (not just in Colorado). It can be found in areas above 5,000 feet in elevation.
The virus is also carried by other small mammals, including ground squirrels, porcupines, and chipmunks. There have been reports of rare cases of Colorado tick fever caused by exposure in a laboratory setting and a blood transfusion.
Colorado tick fever is transmitted through the bite of an infected tick.
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Risk factors include:
- Living or traveling in mountain forest areas at altitudes above 5,000 feet in the western US states (such as Colorado, Utah, Wyoming, Idaho, Montana, Oregon)
- Being in these areas between April and July
If you have any of these symptoms, do not assume it is caused by Colorado tick fever. These symptoms may be caused by other, less serious health conditions. Symptoms usually appear 4-5 days after a tick bite occurs and may last for three weeks:
- High fever
- Severe headache
- Pain behind the eyes
- Sensitivity to light
- Muscle pain
- Abdominal pain
Your doctor will ask about your symptoms and medical history. A physical exam will be done.
Tests may include the following:
- Blood tests to identify the virus
- Blood tests to identify antibodies for the virus
- Other blood tests
There is no specific treatment for Colorado tick fever. Complications are extremely rare and include aseptic meningitis, encephalitis, and hemorrhagic fever. The fever and pain may be treated with acetaminophen (such as Tylenol) and other pain relief medications. It is important to stay hydrated by drinking enough fluids. After a person gets Colorado tick fever, it is believed that he or she will have immunity against re-infection.
To help reduce your chances of getting Colorado tick fever, take the following steps to limit your exposure to ticks:
- Avoid tick-infested areas, especially during warmer months.
- Wear light-colored clothing to better locate a crawling tick.
- Tuck pants into socks when in tick-infested habitats.
- Use tick repellents.
- Regularly inspect and remove ticks from your body and your child’s body when in tick-infested habitats.
- Remove ticks using fine-tipped tweezers by grasping the tick close to the skin’s surface and pulling upward steadily.
- Disinfect tick bites with soap and water.
Brackney MM, Marfin AA, et al. Epidemiology of Colorado tick fever in Montana, Utah, and Wyoming, 1995-2003.
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Colorado tick fever. EBSCO DynaMed website. Available at:
. Updated July 20, 2010. Accessed January 4, 2012.
Colorado tick fever. Utah Department of Health website. Available at:
. Updated August 2001. Accessed January 4, 2013.
Colorado tick fever fact sheet. Oregon.gov website. Available at:
. Accessed January 4, 2013.
Leiby DA, Gill JE. Transfusion-transmitted tick-borne infections: a cornucopia
Transfus Med Rev.
Last reviewed December 2013 by David L Horn, MD, FACP
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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