Around 20,000 new cases of Lyme disease are reported in the USA every year, usually during May and June when the infected ticks are most active, and in the North-Eastern states.
There's no vaccine on the market - mysteriously, the only one available was pulled in 2002 - but there are a few things you can do to help reduce your risk of infection, especially if you live in one of the 10 states where the problem is endemic. (And, in case you're not sure, they are: Connecticut, Delaware, Maryland, Massachusetts, Minnesota, New Jersey, New York, Pennsylvania, Rhode Island and Wisconsin).
Aside from avoiding wooded areas where the ticks live, do a thorough daily self-examination for any ticks that are on your skin - a tick that's on the skin for less than 24 hours is unlikely to infect you - and landscape your yard with a 'buffer zone' of wooden chips between your home and surrounding woodland.
(Source: Journal of the American Medical Association, 2007; 298: 278-9).