Tick-Borne Diseases — A Growing Risk

Ten tick-borne diseases are now recognized in the United States. Three of these have been discovered in the past three decades: Lyme disease in the 1970s, human ehrlichiosis (caused by Ehrlichia chaffeensis) in the 1980s, and a new human ehrlichial infection, human granulocytic ehrlichiosis, in the 1990s.1 Tick-borne diseases have challenged researchers and physicians since studies in the early 1900s established the wood tick (Dermacentor andersoni) as a vector of Rocky Mountain spotted fever. This disease, although uncommon, was widely feared because of its case fatality rate of 70 percent. Deaths decreased dramatically after the introduction of . . .