Areas of Concentrated Risk of Lyme Disease
The eastern half of the United States contains 2 main foci with a high mean density of infected ticks that can cause Lyme disease. One focus is between southern Maine and northern Virginia, and the other is primarily in Wisconsin, northern Minnesota, and an area of northern Illinois.
Concerned that human tick reports are unreliable for determining areas where Lyme disease is endemic, researchers assembled a field staff of 80 tick hunters who meticulously worked at 304 sites from Maine to Florida in the most extensive mapping project of Lyme disease to date.
Armed with 1 m x 1 m pieces of corduroy, the workers set out to trap the black-legged tick Ixodes scapularis, which can carry the Lyme disease pathogen, Borrelia burgdorferi. Investigators led by Maria A. Diuk-Wasser, PhD, assistant professor of epidemiology from Yale School of Public Health, New Haven, Connecticut, determined the proportion of I. scapularis nymphs containing B. burgdorferi DNA.
Using that data, they generated a map showing the Northeast and upper-Midwest as the main endemic areas. Results from the study are published in the February American Journal of Tropical Medicine and Hygiene.
Lyme map. The map shows an elevated risk of Lyme disease from Maine south to Maryland, Northern Virginia, and the Washington DC area. Investigators found a separate region of increased risk in the upper Midwest. The 3 sites marked with red crosses indicate the only sites where investigators collected high numbers of infected tics, but where the statistical model did not accurately predict them as high risk.
