Colorado Tick Fever
Pathogen
Colorado tick fever virus
Carried by
Rocky Mountain wood tick (Dermacentor andersoni)
Colorado Tick Fever is a viral infection carried by the Rocky Mountain wood tick at higher elevations in the Western US. It often produces a distinctive 'biphasic' fever — a fever that breaks and then returns a few days later.
Symptoms
- Fever (often in two phases)
- Headache, muscle aches
- Fatigue that can linger for weeks
Testing
Antibody testing and PCR.
Labs often used in the Lyme community:
See our Testing Guide to understand your options.
Geography
Rocky Mountain states at elevations of roughly 4,000–10,000 feet.
Explore the Where Ticks Live map to see what's carried in your region.
Treatment overview
No specific antiviral — supportive care. Most people recover, though fatigue can persist.
Frequently asked questions
Where do people catch it?
At higher elevations in the Rocky Mountain region, from the Rocky Mountain wood tick — often during spring and summer hikes or camping.