Key points
- Colorado tick fever is caused by a virus typically transmitted through the bite of an infected Rocky Mountain wood tick (Dermacentor andersoni).
- Colorado tick fever virus circulates in the environment between ticks and small rodents found in the Rocky Mountains.
- Colorado tick fever virus also is rarely transmitted through blood transfusion.
Primary cause
Colorado tick fever is caused by a virus that is found in the western United States and western Canada at 4,000–10,000 feet above sea level.
How it spreads
- People become infected with Colorado tick fever virus from the bite of an infected Rocky Mountain wood tick (Dermacentor andersoni).
- Ticks become infected with the virus when they feed on small rodents, such as squirrels, chipmunks, and mice, that have the virus in their blood.
- After the tick becomes infected, it can pass the virus to people or other animals while it feeds.
- The virus is not transmitted from person to person, except in rare instances by blood transfusion and from mother to baby around the time of birth (perinatal).
For Public Health
Transmission