Public health officials say more Massachusetts residents are being diagnosed with Lyme disease, and many of them are picking up the tick-borne ailment in areas of the state where it was relatively rare a decade ago.
State Department of Public Health figures show that the disease, once most common on Cape Cod and the Islands, is now seen more in Middlesex, Norfolk, and Worcester counties.
There were 4,042 Lyme disease cases statewide last year, compared with 1,194 in 2000.
People get the disease from bacteria passed on by ticks that attach themselves to the skin.
Specialists tell The Boston Globe that the disease is spreading as the tick-carrying deer population explodes and housing developments encroach on natural habitats.
The disease causes flulike symptoms and can be treated by antibiotics.