EVEN FROZEN AND DUNKED IN ALCOHOL, LURKING BACTERIA MENACE TRAVELERS
By ERIK ECKHOLM
Published: July 2, 1985
AFTER a sweltering morning of traipsing through temples in Yucatan, or a parched afternoon of gazing at pyramids in Giza, a lukewarm soda just won't do.
''Ice?'' queries the bartender, disingenuously ignoring the psychic turmoil his question triggers.
Does freezing kill those invisible bugs in the water? If not, alcohol surely will, won't it? The uncertainty could well require a scotch.
The safety of ice in the third world, a question that has long nagged even intrepid travelers, has finally been addressed by modern science.
Three medical researchers, Herbert L. DuPont, D. Lynn Dickens and Philip C. Johnson of the University of Texas, have studied the extent to which four common bacterial enteropathogens - the agents that cause intestinal distress - survive in an ice cube. They also determined, in rigorous tests, how icebound bacteria fare when the cube is submerged in various liquids, including water, cola, scotch and soda, straight scotch and 86-proof tequila.
Their report, in a recent issue of The Journal of the American Medical Association, found that although ice is safer than tap water, it can still cause gastric chaos. About 10 percent of the bacteria in contaminated water can withstand weeks of freezing.
But when ice is a must, the risk of diarrhea can be cut further by immersing the ice in undiluted liquor. A stiff dose of alcohol will finish off many of the remaining harmful microbes, the report indicated.
In laboratory tests, cola and soda water did not faze the iceborne bacteria, which multiplied as the ice melted. A scotch and soda only ''slightly inhibited'' the recovery of the pathogen populations. Undiluted 80-proof scotch did better, and in 86-proof tequila ''there was marked inhibition of all the organisms.''
Lest travelers start packing extra flasks, however, Dr. DuPont warned that in his opinion ''the concentration of alcohol has to be so high'' to suppress pathogens adequately that drinking for gastric safety is ''not really a practical recommendation.''
For the alcohol-shy, too, the study's message is a mixed one. The prolonged freezing of contaminated water does kill 90 percent of the dangerous agents, but whether this makes the ice safe depends on which particular pathogens inhabit it.
The most common cause of traveler's diarrhea, accounting for some 40 percent of cases, is the bacterial species Escherichia coli. This microbe tends to cause illness only when ingested in high numbers, so the sharply reduced population in an ice cube does not pose much of a threat. Likewise, unless the original water was extremely contaminated, freezing kills off Salmonella bacteria to below the danger point.
But Shigella bacteria, which cause dysentery and were found in a study to be responsible for 15 percent of traveler's afflictions in Mexico, are much more potent. Studies have shown that as few as 200 of the microscopic Shigella organisms are capable of making a person acutely ill. Far more than that can survive in ice; viable Shigella bacteria have been recovered from ice that had been frozen solid for two months.
For that matter, hazardous numbers of this hardy microbe can survive a bath in straight tequila.
''You are running a risk when you put ice in a drink,'' Dr. DuPont concluded. ''I don't do it myself.''
In any case, he noted, contaminated food rather than water is the major source of traveler's intestinal infections. ''Anything sitting out buffet style - things like salads, cold chicken, desserts, leafy vegetables and the sauces sitting on the table -should be avoided,'' he said. Even cooked foods are unsafe unless they are served right off the fire.
The safest foods are steaming hot items, citrus fruits, dry foods like bread and tortillas and sugary substances like jelly.
A greatly underappreciated hazard for travelers in third world countries, Dr. DuPont said, is airplane food, even the fare on major Western airlines. ''I see people being careful in a place like Egypt, then they get on a Pan Am or T.W.A. plane and they think they're safe,'' he said. Often, people develop diarrhea on their return home because of something they ate on the airplane, Dr. DuPont said.
Food poisoning on planes is common enough in the United States and Europe, he noted, and the formidable impediments to sanitary food preparation and serving on an airplane are multiplied in less developed countries, where harmful bacteria are more prevalent.
What about airplane ice? ''I'd never take ice in my drink on a plane leaving from Latin America, Africa or southern Asia,'' Dr. DuPont said.
Overall, do the Texas findings mean that health-conscious wanderers in exotic lands are duty-bound to imbibe straight liquor?
''We don't want to encourage people to drink a lot of booze,'' Dr. DuPont said. ''They'll walk out of the bar and fall into a manhole.''