Incidence and Distribution of Lyme Disease in the United States

Lyme disease has a wide distribution in northern temperate regions of the world. In the United States, the highest incidence occurs in the Northeast, from Massachusetts to Maryland and the North-central states, especially Wisconsin and Minnesota.

In 2002, more than 23,000 cases of Lyme disease were reported in the U.S., the highest number ever reported. This increase could be caused by an increase in human contact with infected ticks and enhanced reporting of cases.

Ten states have consistently reported an incidence of Lyme disease higher than the national average:  Connecticut, Delaware, Maryland, Massachusetts, Minnesota, New Jersey, New York, Pennsylvania, Rhode Island and Wisconsin. During 2003-2005, 64,382 Lyme disease cases were reported to CDC, of which 59,770 cases (93%) were reported from these 10 states. Similar data was reported in 2006 (see map below).

Lyme disease cases by state, 2006. CDC.