Figure 1: Estimated geographic distribution of lone star ticks (above) and blacklegged ticks (below)

Map of the United States showing the approximate distribution of the Lone Star tick.  The area affected is the eatern half of the country.
Approximate distribution of the Blacklegged tick in the United States of America

Ehrlichiosis is the general name used to describe diseases caused by the bacteria Ehrlichia chaffeensis, E. ewingii, or E. muris eauclairensis in the United States. The majority of reported cases are due to infection with E. chaffeensis.

Ehrlichiosis caused by E. chaffeensis and E. ewingii is most frequently reported from the southeastern and south-central United States, from the East Coast extending westward to Texas.