Visit The CDC Site For Health Warnings

The Center for Disease Control has a great site for travelers: CDC's Travelers' Health. Take a look at the list under Travel Notices to see if there is something about a country you will be visiting. New alerts show up there. Also click on Destinations to read medication and vaccination recommendations for the area you'll be in.

The CDC also publishes The Yellow Book every two years. A reference book with advice for international travelers about possible health risks, it meant for professionals but can be a great resource for anyone. It can be purchased at online stores like Amazon. A Kindle version is even available.