The vector of Colorado tick fever is Dermacentor andersoni, the Rocky Mountain wood tick, which is found in small mammals. The virus is an RNA virus of the genus Coltivirus. This intraerythrocytic arbovirus is found in the Western United States at altitudes of 4,000 to 10,500 feet. 83 cases were reported between 2002-2012, but only six states require reporting. Reporting is voluntary in other states.