NEW YORK, NY (AP)-- Health officials say the geographic areas where Lyme disease is a bigger danger have grown dramatically.
U.S. cases remain concentrated in the Northeast and upper Midwest. But now more areas in those regions are considered high risk.
A new report shows 260 counties where the risk of catching Lyme disease from tick bites is at least twice the national average, up from 130 a decade earlier.
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.
The article was published online Wednesday in a journal, Emerging Infectious Diseases.