What is colorado tick fever?

Colorado Tick Fever
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Colorado tick fever: Overview

Colorado tick fever is caused by a virus that you get from a tick bite. Some people remember getting a bite. Others don't. The symptoms usually start about 1 to 14 days after you get the tick bite. Symptoms include muscle aches, fever, chills, and headache. Sometimes the fever goes away for a few days and then comes back. Some people also notice that they are sensitive to light.

The illness usually gets better in about a week. But some people may feel tired and weak for a month or two. Treatment can reduce the symptoms. Most people with the illness have mild symptoms and recover completely.

Colorado tick fever occurs in the mountain regions of the western United States and Canada. The tick that carries the virus is the Rocky Mountain wood tick (Dermacentor andersoni). It is found at an elevation of 4,000 to 10,000 feet.

Do not donate blood or bone marrow for 6 months after you have been diagnosed with Colorado tick fever. The virus may stay in your blood for several months. If you donate blood or marrow, you may pass the disease to other people.

Colorado tick fever

Colorado tick fever is an infectious viral disease that can be passed to humans by ticks. Colorado tick fever occurs in the mountain region of the western United States.

Symptoms usually start 1 to 14 days after you get the tick bite. Symptoms of Colorado tick fever include:

  • Fever and chills.
  • Headache, often severe.
  • Muscle aches (myalgias).
  • Sensitivity to light (photophobia).

Medical treatment can help relieve the symptoms of Colorado tick fever.

How can you care for yourself when you have Colorado tick fever?

Easing symptoms

  • Rest when you feel tired.
  • Ask your doctor if you can take an over-the-counter pain medicine, such as acetaminophen (Tylenol), ibuprofen (Advil, Motrin), or naproxen (Aleve). Read and follow all instructions on the label.
  • To prevent dehydration, drink plenty of fluids. Choose water and other clear liquids until you feel better. If you have kidney, heart, or liver disease and have to limit fluids, talk with your doctor before you increase the amount of fluids you drink.


  • When you come in from outdoors, check your body for ticks. Make sure to check your groin, head, and underarms.
  • Cover as much of your body as you can when you work or play in grassy or wooded areas. Wear a hat, a long-sleeved shirt, and long pants with the legs tucked into your socks. Keep in mind that it is easier to spot ticks on light-colored clothes.
  • Use insect repellents with DEET. Do not use these products on your hands, eyes, and mouth.
  • Use products that contain 0.5% permethrin on your clothing and outdoor gear, such as your tent. You can also buy clothing already treated with permethrin.

Colorado tick fever: When to call

Call your doctor now or seek immediate medical care if:

  • You are confused or can't think clearly.
  • You have a headache or stiff neck.
  • You have a new or worse rash.
  • You have symptoms of infection, such as:
    • Increased pain, swelling, warmth, or redness.
    • Red streaks leading from the area.
    • Pus draining from the area.
    • A fever.

Watch closely for changes in your health, and be sure to contact your doctor if:

  • You are not getting better as expected.

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The content above contains general health information provided by Healthwise, Incorporated, and reviewed by its medical experts. This content should not replace the advice of your healthcare provider. Not all treatments or services described are offered as services by us. For recommended treatments, please consult your healthcare provider.