Lyme Disease Tick Spreading Rapidly in US

The geographic areas where Lyme disease is a bigger danger have grown dramatically, according to a new government study published Wednesday

U.S. cases remain concentrated in the Northeast and upper Midwest. But now more areas in those regions are considered high risk.

"The risk is expanding, in all directions," said the lead author, Kiersten Kugeler of the Centers for Disease Control and Prevention.

There are now 260 counties where the risk of catching Lyme disease is at least twice the national average, up from 130 a decade earlier, the report shows.

Lyme disease is most common in wooded suburban and far suburban counties. Scientists aren't sure why high-risk areas are expanding, but it likely has something to do with development and other changes that cause the mice, deer and ticks that carry the bacteria to move, Kugeler said.

Overall, 17 states have high-risk counties. The entire state of Connecticut, where the illness was first identified in 1975, has been high-risk for decades. Now, high-risk zones encompass nearly all of Massachusetts and New Hampshire and more than half of Maine and Vermont.

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