Lyme disease is a debilitating, sometimes fatal infection passed to humans by infected blacklegged ticks. According to the Centers for Disease Control and Prevention, there are more than 30,000 cases of the disease each year nationwide. Due to underreporting, the actual incidence may be as high as 10 times the reported figure.
Lyme disease has been reported in every state except Hawaii at least once since 2005. However, the disease tends to be heavily concentrated in certain parts of the country. About 86% of confirmed cases of Lyme disease in the United States were reported in the 12 states on this list — which are largely concentrated in the Northeast and mid-Atlantic regions.