Lead author Dr. Maria A. Diuk-Wasser of the Yale School of Public Health and colleagues found high infection risk confined mainly to the Northeast, Middle-Atlantic and Upper Midwest, and low risk in the South.
"There has been a lot of discussion of whether Lyme disease exists outside of the Northeast and the upper Midwest, but our sampling of tick populations at hundreds of sites suggests that any diagnosis of Lyme disease in most of the South should be put in serious doubt, unless it involves someone who has traveled to an area where the disease is common," Diuk-Wasser said in a statement. "We can't completely rule out the existence of Lyme disease in the South, but it appears highly unlikely."
The study did not examine risk in the West where Lyme disease is believed to be confined to areas along the Pacific Coast.
Researchers at the Yale School of Public Health, Michigan State University, University of Illinois and University of California, Irvine, through a cooperative agreement with the Centers for Disease Control and Prevention assembled a field staff of more than 80 tick hunters.
From 2004 to 2007, they combed through 304 individual sites from Maine to Florida and across the Midwest. They used a square of corduroy cloth and counted the black-legged tick that is the main carrier of the Lyme disease pathogen.
The findings were published in the American Journal of Tropical Medicine and Hygiene.