In the 19th Century, settlers and visitors to the Rocky Mountain region of North America mentioned "mountain fever" as a cause of morbidity and occasional mortality. "Mountain fever" likely was any of a number of febrile illnesses, including typhoid fever, Rocky Mountain spotted fever (RMSF) and Colorado tick fever.
< Landscapes where viral incidence is high occur in western USA and Canada; they typically have have open stands of ponderosa pine, and shrubs on dry, rocky surfaces. These specific ecologic characteristics comprised specific habitats for the small mammals on which the ticks depend for both blood meals and shelter, which include the golden mantled ground squirrel [Spermophilus lateralis], porcupine [Erethizon dorsatum], least chipmunk [Tamias minimus], deer mouse [Peromyscus maniculatus], and bushy-tailed woodrat [Neotoma cinerea].
The geographic distribution, principal arthropod vector, and vertebrate hosts of CTF virus have been well established for many years, yet this disease continues to be underrecognized and underreported to health departments.