Oral Rehydration Therapy for cholera and diarrheal disease

Cholera killed by dehydration, and before oral rehydration therapy, the only effective treatment was intravenous fluid replacement. In epidemic conditions in South and Southeast Asia, Africa, and Latin America, that constraint was lethal: IV fluids required sterile equipment, trained staff, and a functioning supply chain, none of which reliably existed where cholera killed the most people. Case fatality rates in untreated or poorly resourced settings routinely exceeded 20 to 30 percent.

The scientific basis for a different approach had been accumulating through the 1960s. Researchers including Robert Phillips had shown that glucose administration accelerated sodium absorption in the small intestine, and work at the Cholera Research Laboratory in Dhaka was clarifying the mechanism: cholera toxin causes massive secretion of sodium and water into the gut lumen by constitutively activating adenylate cyclase in enterocytes, but it does not disable the glucose-sodium cotransporter on the brush border. That transporter could still pull sodium, and water with it, across the epithelium if glucose was present in the lumen.

David Nalin and Richard Cash, working at the Cholera Research Laboratory in Dhaka in 1968, conducted a controlled trial that put this physiology directly to clinical test. They gave adult cholera patients an oral glucose-electrolyte solution and measured IV fluid requirements against controls. The oral solution cut IV fluid needs by approximately 80 percent. Patients who would otherwise have required continuous intravenous infusion were kept in fluid balance with a drink that could be prepared from sugar, salt, and clean water.

The simplicity of the solution was not incidental to its impact. Norbert Hirschhorn and colleagues working in parallel with cholera patients in the same period contributed supporting evidence, and the global health implications became clear quickly. Cholera struck hardest in places where hospitals were overwhelmed or absent. A therapy that community health workers could mix and administer without needles or electricity was a qualitatively different tool from anything previously available.

WHO and UNICEF standardized an oral rehydration salt formulation in 1975, and mass production and distribution followed over the next two decades. The WHO later introduced a reduced-osmolarity formulation in 2002 after trials showed it further reduced stool output and the need for supplemental IV fluids. A 1978 Lancet editorial called the discovery behind oral rehydration therapy potentially the most important medical advance of the century, and later estimates credited the therapy with preventing millions of child deaths a year from all-cause diarrheal disease, not cholera alone.