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Most cases of diarrhea can be traced to food or water tainted by 100 or so intestinal bugs, most commonly rotavirus, E. coli, shigella, campylobacter and salmonella. Thumb sucking doesn't help; it can lead to what doctors call fecal-oral contamination. "Toddlers will always pick up things and put them into their mouths and, if you don't have a clean environment, that can lead to diarrhea," says Therese Dooley, until recently a unicef project officer in Ethiopia. Infection triggers a cascade of events that can cause diarrhea, if left untreated, to escalate from an unpleasant experience to a life-threatening condition. Normally, 50-75% of the human body is water. The small intestine serves as its key pumping station, absorbing water and nutrients through its walls. There, nutrient-rich fluids enter the bloodstream, which transports them to other parts of the body. But when the intestine detects a pathogen in its midst, it stops soaking up fluids and disgorges its contents in a watery rush of stools. The consequence is what we know as dehydration.
Oral rehydration treatment can reverse dehydration in more than 90% of patients, even in cases of the severe diarrhea caused by bugs like rotavirus and cholera. When the solution reaches the small intestine, the sugar is moved from the hollow part of the intestine into its mucosal lining through the villi, small fingerlike projections on the intestinal wall. "It's like having a chemical needle in the intestinal tract," says William Greenough, a professor of medicine at Johns Hopkins School of Medicine in Baltimore, Maryland, and a former director of ICDDR. Sugar's chemical properties allow salt to be absorbed more efficiently. The salt then promotes the absorption of water into the capillaries within the intestinal wall, which carry the water and electrolytes to other parts of the body and restore fluid balance.
The connection between diarrhea and fluid loss was first noted in 1830 by a surgeon working for the British East India Company in Calcutta. But interest in treating diarrhea didn't gain ground until devastating cholera epidemics swept the subcontinent in the middle of the last century. Fluid loss from cholera-related diarrhea occurs so rapidly that its victims can die within four to eight hours or, as lore has it, before they can dig their own graves. Cholera is still a leading cause of diarrhea in Bangladesh's southern Ganges River basin. Vaccines preventing cholera have never been completely effective or long-lasting, so when ICDDR was established as the Cholera Research Laboratory in 1960, its mission was to evaluate such treatments. By the late 1960s, the facility had begun experimenting with oral rehydration and, within a few years, fatalities among its diarrhea patients had dropped from 50% to zero. Across the Bangladeshi delta, oral rehydration was also gaining ground at the Johns Hopkins Center for Medical Research and Training in Calcutta. Teams at both centers knew they had an effective treatment but they faced resistance from a profession that dismissed such a basic remedy as inferior to costlier IV saline fluids.
The opportunity to prove oral rehydration's worth came in the form of a disaster. When Bangladesh's war for independence from Pakistan broke out in 1971, 9 million refugees poured into India, bringing cholera with them. Dilip Mahalanabis, an Indian doctor who had participated in the oral rehydration trials at the Johns Hopkins Center in Calcutta, began using IV saline treatment at a border camp, but within weeks his supplies were exhausted. Amid awful scenes in which people walked for days only to die, Mahalanabis and his team drew on their experiences in Calcutta. They formed an assembly line to weigh out correct proportions of rehydration ingredients in plastic bags, sealed the bags with an iron, and mixed the powder with water so patients' friends and relatives could collect it in mugs. "We converted the library at Johns Hopkins into a factory," Mahalanabis, now 79, recalls. "We brought in drums with side-taps, filled them up and sent them to the field. We were essentially using people to experiment on. But we were pushed to the wall. We had no choice." Using lay people to administer the treatment while health workers replenished supplies was controversial. Doctors had long assumed that, in untrained hands, rehydration solution might be prepared in the wrong concentration and kill more patients than it saved.