The Centers for Disease Control and Prevention (CDC) has developed this national Lyme disease risk map identifying areas of the U.S. as minimal or no risk, low risk, moderate risk, or high risk for predicted Lyme disease.
Areas at high or moderate risk include many counties in the Northeast U.S. (including Connecticut, Maryland,
Massachusetts, New Jersey, New York, Pennsylvania and Rhode Island), some areas around the Great Lakes (including Wisconsin, Illinois and Minnesota) and an area in Northern California.
The CDC notes that, of course, the true relative risk in any given county compared with other counties might differ from that shown here and might change from year to year.
Lyme disease is caused by Borrelia burgdorferi, a bacterium carried in the gut of certain ticks. When these infected ticks attach to the human body (often in armpits, groin, scalp, or other hairy, hidden body areas), they slowly feed, and within 36-48 hours they may transmit B. burgdorferi to their human host. Young ticks are especially abundant, and are seeking hosts in late spring and early summer, although adult ticks can transmit infection as well.