Once found mostly on Cape Cod and surrounding islands, the bacterial disease is showing up in areas across the state, The Boston Globe reported Monday.
Previously, cases were largely restricted to people who had visited Cape Cod and suffered tick bites, the newspaper said.
"Now they're living in Charlton, they're living in Northborough, they're living in Westborough," Dr. Richard Ellison, hospital epidemiologist at UMass Memorial Medical Center in Worcester, said. "And they're not traveling to the Cape.''
The state Department of Public Health says cases have increased fourfold in Middlesex, Norfolk and Worcester counties since 2000.
The disease is spreading, experts said, as deer populations grow and human developments encroach on natural habitats. Hundreds of ticks can hitch a ride on a single deer, and one female tick can lay 2,000 or more eggs.
"This has been an accident waiting to happen,'' said Dr. Thomas Treadwell, director of an infectious disease clinic in Framingham, Mass. "If you don't have the deer, you don't have the tick. And if you don't have the tick, you don't have the disease. But we now have the perfect habitat here.''
Lyme disease causes flu-like symptoms although serious cardiac and neurological complications can occur in some patients, the Globe reported.