In the grand scheme of things, Lyme disease is a fairly new scientific discovery. First traced back to ticks in the late 70s and early 80s, the tick-borne illness – which can cause a rash, fever, muscle and joint pain, neurological complications, and even face paralysis – is spread by only two of the nearly 50 species of ticks in the United States. Historically, most Lyme cases were limited to a small region, including the Great Lakes area and northeastern US. But thanks to changing temperatures, animal migration, and shifts in land usescientists say tick territory is expanding. So what does that mean for Lyme disease risk… and do you have to be worried about it in your own backyard?