Symptoms typically begin to develop 4 days following the tick bite, but may be as long as 20 days.

Initial symptoms of Colorado tick fever include:

• Fever
• Excessive sweating
• Muscle aches
• Joint pains
• Headache

The above symptoms are followed by a symptom-free period, after which additional symptoms begin.

Additional symptoms of Colorado tick fever include:

• Increased sensitivity to bright light
• Nausea
• Vomiting
• Weakness or fatigue
• Rash

Rare symptoms of Colorado tick fever include:

• Confusion
• Lethargy:
• A condition of excessive sleepiness or drowsiness.