Prospective study of coinfection in patients with erythema migrans.

The frequency of coinfection with Borrelia burgdorferi and either Anaplasma phagocytophila or Babesia microti among patients with erythema migrans, the initial skin lesion of Lyme disease, was assessed in 2 mainland locations in Rhode Island and Connecticut in a 4-year prospective study. Of the 93 patients with culture-proven erythema migrans, 2 (2%) patients had coinfection with A. phagocytophila and 2 (2%) had coinfection with B. microti. We concluded that the frequency of coinfection with these agents was low among patients with erythema migrans in the study areas.