University of Wisconsin–Madison

Ehrlichia chaffeensis

Echaff cases 2012

Figure 1.  Ehrlichia chaffeensis is a bacterial pathogen transmitted by the lone star tick, Amblyomma americanum.  The map above represents confirmed and probable cases by county.  Many of these cases are in people with travel history to areas of the southern US where lone star ticks are more abundant but there are a few cases that appear to have been contracted in Wisconsin.   Additional maps for all cases and historical data can be found at