Colorado tick fever

noun

Col·​o·​ra·​do tick fever ˌkäl-ə-ˈrad-(ˌ)ō-, -ˈräd- 

: a mild disease of the western United States and western Canada that is characterized by intermittent fever, malaise, headaches, myalgia, and the absence of a rash and is caused by a reovirus (species Colorado tick fever virus of the genus Coltivirus) transmitted by the Rocky Mountain wood tick

Colorado tick fever is caused by a virus that replicates in blood-forming stem cells, prompting blood count to drop.

—Daniel C. Weaver, Discover