By Alastair Lawson BBC correspondent in Dhaka

The biggest hospital for diarrhoea patients in the Bangladeshi capital, Dhaka, was celebrating on Saturday.

In the beginning 5 million children were dying from diarrhoea, but now it's down to a bit more than 1 million

Professor LA Persson, Dhaka

The internationally funded Centre for Health and Population Research says that its Oral Rehydration Solution (ORS) has now saved 40 million lives in Bangladesh and other developing countries.

The centre's researchers developed ORS in the late 1970s, and its use has been successfully expanded across the world.

ORS is a simple mixture of drinking water, mineral salts and sometimes sugar.

It is today credited with ensuring that diarrhoea is no longer the most common killer of children in the world.

Lives saved

It is estimated by the centre that ORS, which is relatively cheap and easy-to-use, still saves 3 million children annually.

Diarrhoea was the biggest killer of children

The British medical publication, The Lancet, described ORS as the most important medical advance in the 20th century.

The figures released by the centre seem to bear that out.

"This has been a world-wide effort and from the very beginning estimates have been made of the number of lives that were saved," said Professor Lars Ake Persson of the Centre for Health and Population Research.

"In the beginning 5 million children were dying from diarrhoea, but now it's down to a bit more than 1 million."

Further development

The centre's figures show that over the past two decades, ORS has saved millions of lives in Bangladesh alone.

Poverty makes children especially vulnerable

They show that Bangladeshis use 100 million packets of ORS each year.

It is relatively cheap and easy-to-use. A mother can administer treatment to her children without contacting doctors.

Scientists at the centre say that every year there are still 1.5 million people throughout the world who die of diarrhoea.

They say that their aim now is to improve ORS treatment so that the formula works even quicker on diarrhoea sufferers.