Figure. Location of ticks, Rickettsia parkeri in ticks, and human cases of rickettsiosis in the United States. Green shading indicates approximate distribution of Amblyomma americanum ticks, which completely overlaps with the known or suspected distribution of A. maculatum. Yellow circles indicate locations where R. parkeri was detected in A. americanum ticks (this study). Red circles indicate locations of confirmed or suspected cases of R. parkeri infection in humans (11).