HGE and HME have been recognized as distinct clinical conditions for only 5 and 10 years, respectively, and much information regarding their ecology and epidemiology remains uncertain. The nonspecific character of the illness complicates this incomplete knowledge, as an unknown percentage of infections are likely misdiagnosed. Ehrlichiosis should be considered in any patient presenting with flu-like illness and history of a tick bite. Although expanding, diagnostic support for human ehrlichioses is currently limited to a few regional academic and public health laboratories. Healthcare providers should educate themselves regarding the clinical presentation of ehrlichioses and the availability of diagnostic resources in their area.