The British Medical Journal is launching a competition to decided the greatest medical breakthrough.
Present-day medical experts are championing discoveries from the last 166 years.
Olivier Fontaine, medical officer at the World Health Organisation (WHO), Paul Garner, professor of community health at the Liverpool School of Tropical Medicine and MK Bhan, Ministry of Science and Technology, Government of India are championing oral rehydration therapy.
The influx of 6,000 refugees from the India-Pakistan war in the early 1970s led to the development of the treatment.
Children's lives have been saved by rehydration therapy
Cholera took hold, and nothing seemed able to contain it until a US doctor, Dilip Mahalanabis, decided to use his new oral rehydration solution to replace the water and electrolytes which were being lost through vomiting and diarrhoea.
It was a success, and over the next eight weeks, deaths fell to less than 1%.
There was scepticism over the treatment, but a WHO expert visited the camps and was stunned by its success realised it could be used to treat childhood diarrhoea in any setting.
Children in developing countries can be infected with diarrhoea as often as every four months, and it can kill.
In the 1980s, nearly five million children died each year from diarrhoea. In 2000, that figure had fallen to 1.8 million.
Over the last 25 years, an estimated 50 million children's lives have been saved by the therapy.
But Dr Fontaine, Professor Garner and Mr Bahn say: "It is a tragedy that 1.8m preventable deaths from diarrhoea still occur each year because children do not have access to this cheap, easily prepared solution."