Human ehrlichiosis--Maryland, 1994.

Ehrlichiosis is an emerging tickborne infectious disease caused by obligate intracellular, gram-negative rickettsia that infect leukocytes. Human monocytic ehrlichiosis (HME) is caused by Ehrlichia chaffeensis and is believed to be transmitted by Amblyomma americanum (the Lone Star tick). Most HME cases have been reported in southeastern and south-central states. During May-July 1994, five cases of serologically confirmed HME were identified among residents of Maryland. All five persons lived near the Chesapeake Bay and had antecedent histories of tick exposure. This report summarizes the clinical and epidemiologic features of these cases and the results of serologic testing at CDC of specimens from Maryland residents with suspected tickborne infection.