Oral rehydration solutions (ORS) are indeed the most cost-effective medical treatment known, costing only a few pennies worth of sugar, salt, and clean water, which can reduce the mortality of toxigenic secretory diarrhea 50-fold or more. 

In 1849, Italian scientist Filippo Pacini identified comma-shaped organisms termed vibrios in the gastrointestinal contents of corpses of cholera victims, hypothesizing these organisms to be responsible for the copious intestinal fluid secretion characteristic of the disease, and proposed intravenous NaCl as a remedy. His theory was 30 years later confirmed by the eminent microbiologist Robert Koch. 

William B. O′Shaughnessy first published a description of fluid resuscitation for cholera in 1831 and proposed intravenous salt solutions, however not for their volume-expanding effects but for their oxygen content, recommending KNO3 or KClO3 as opposed to NaCl. 

Dr. Thomas Latta and his collaborators refined this practice a year later and initiated the practice of infusing massive amounts of saline solution, which caused immediate recovery of intravascular volume and symptom improvement.

In the 1940s, a deeper understanding of blood electrolyte composition and whole-body fluid and electrolyte dynamics allowed the safe and effective delivery of scientifically based intravenous fluid and electrolyte therapy, eventuating in the development of modern intravenous solutions. Oral fluids, regarded mostly as palliative, were not the first-line therapy then.

Robert Crane, in 1960 showed that luminal sodium ions increased the glucose transport rate in rat ileum work, which made the foundation study for ion co-transport mechanisms. As a result, 1968 witnessed numerous studies conducted in India and Pakistan reporting that glucose-containing solutions perfused in the intestine can substantially decrease stool volume, confirming the efficacy of ORS in epidemic cholera. Since then, there have been many publications documenting refinements of the original sodium-glucose-containing solution by adding organic components.

These studies further facilitated many more advancements in the Treatment of Toxigenic Diarrhea and cholera, including cholera toxin-induced adenylate cyclase to generate cAMP, adenylate cyclase 6 specifically induced by cholera toxin, development of small molecule inhibitors of the cystic fibrosis transmembrane regulator (CFTR) anion channel for toxigenic diarrhea and much more, which are still serving to reduce child mortality globally.

Kaunitz JD. Oral Defense: How Oral Rehydration Solutions Revolutionized the Treatment of Toxigenic Diarrhea. Dig Dis Sci. 2020 Feb;65(2):345-348. doi: 10.1007/s10620-019-06023-5. PMID: 31900719; PMCID: PMC7193728