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 within 14 days (average of 3 to 6 days) of 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.