The pathogen is a double-stranded RNA virus of the Orbivirus genus. Between 200 and 300 cases are reported each year in the mountain regions of Colorado, Wyoming, Montana, Idaho, Washington, Oregon, California, New Mexico, Nevada, Utah, and South Dakota. The illness begins 3 to 6 days after inoculation, with an abrupt onset of constitutional complaints. In the western forested mountains above 300 meters, Ornithodoros hermsii serves as the vector for Borrelia hermsii. The incubation period for relapsing fever is generally 7 days but ranges from 4 to 18 days.
Illness usually begins with an abrupt onset of systemic malaise.
Borrelia burgdorferi is the spirochete that causes this illness. Ixodes scapularis in eastern and upper midwestern states and Ixodes pacificus in western states serve as the vectors for human inoculation. Lyme disease may cause both an acute and chronic multisystem illness. Lyme disease is typically divided into three stages.9 Stage 1 is the early localized stage occurring 7 to 10 days after infection. This is the point at which the typical dermatitis, erythema migrans, develops at the site of the tick bite.