Diarrhoea, which can be corrected through inexpensive and simple means, kills an estimated 1.5 million children each year, a UN study released on Wednesday showed.
The number of children in the developing world dying of diarrhoea outpaces the combined youth fatalities from AIDS, malaria and measles, according to research done by the World Health Organisation (WHO) and the UN Children's Fund (Unicef).
Ann Veneman, the head of Unicef said this was a "tragedy."
"Inexpensive and effective treatments for diarrhoea exist, but in developing countries only 39 percent of children with diarrhoea receive the recommended treatment," Veneman said.
A new vaccine was developed for Rotavirus, an organism responsible for more than 40 percent of all diarrhoea, but it remains out of reach in most of the developing world, the UN said.
Well over two billion people globally do not have adequate sanitation facilities, UN figures have shown, while 88 percent of diarrhoeal deaths are attributable to unsafe water, inadequate sanitation and poor hygiene.
"Access to clean water and good hygiene practices are extremely effective in preventing childhood diarrhoea," WHO and Unicef said jointly.
Meanwhile, the UN was pushing forward Thursday a Global Hand-washing Day, the second time the international body was supporting such an initiative.
The day "shines a spotlight on the importance of hand-washing with soap and water as one of the most effective and affordable health interventions," Unicef said ahead of the event, which is running under the slogan "clean hands save lives."
In one example, the UN estimated that hand washing with soap can reduce the incidence of diarrhoeal disease by over 40 percent, though many in the world remained without access to the basic products required for this simple and inexpensive act.