Traveling to Africa or Southeast Asia? Malaria and dengue fever are the big worries. In the Caribbean and South America, it’s infections from worms and other parasites. In south-central Asia, respiratory illness.

Visitors to exotic locales have long been warned not to drink the water. But tourists also face plenty of other health dangers – including food, mosquitoes and bugs on the ground. Now, the records of ill travelers treated at a network of 30 travel-medicine clinics on six continents, called GeoSentinel, have yielded the most comprehensive picture yet of the illnesses most likely to strike visitors to particular regions of the Third World.

“This is a real blueprint” for doctors, said Dr. David Freedman, lead researcher of a study reported in today’s New England Journal of Medicine. “Where the traveler has returned from really determines … what diagnoses you should worry about and what you should test for.”

Each year, about 8 percent of the more than 50 million travelers to developing countries become sick enough to seek care during their trip or when they return home. Depending on the destination, up to two-thirds become sick, most with short-lived diarrhea, skin problems and respiratory infections.

GeoSentinel collected records on 17,353 ill tourists treated from 1996 through 2004, after their return home from 230 developing nations. The records showed many had lingering diarrhea from infections by parasites, now more common than bacterial diarrhea; dengue fever has become more prevalent than malaria in most regions; and infections from tick bites are now a big problem in sub-Saharan Africa.

GeoSentinel shares its findings with health agencies; information for specific locations may be found at www.cdc.gov/travel.

Dr. Bradley Connor, president of the International Society of Travel Medicine, said data from the study can help remind travelers to take precautions before departure.

“People spend a lot of time researching hotels and airfares, and they don’t give much thought to the health issues that could potentially ruin the trip,” he said.