Did you swim in a parasite-laden river or lake?

[CNN reports](http://www.cnn.com/2006/TRAVEL/01/12/exotic.diseases.ap/index.html?section=cnn_travel) on a new study of Third World diseases and what doctors have learned. The tip is to tell doctors where you’ve travelled, if you come back sick, and tell them about this study. The most prevalent diseases are [Legionnaires' disease](http://en.wikipedia.org/wiki/Legionnaires%27_disease), [dengue fever](http://en.wikipedia.org/wiki/Dengue), and infections from tick bites.