By Alastair Lawson
BBC News, Sunderbans
Clean water is vital in stopping the spread of disease
One week after a devastating cyclone hit Bangladesh, thousands of people remain homeless and much needed aid is slow to arrive.
One of the key problems facing the authorities now is distributing clean drinking water.
Some aid agencies warn that unless that and other vital supplies arrive soon, the number of people who will die in the days after the cyclone could exceed the number who perished last Thursday night when the storm struck.
The problem is vividly illustrated by a visit to the village of Tafalbari on the fringes of the world's largest mangrove forest, the Sunderbans, in the south-west of the country.
There are relatively few tube wells here.
One major advantage of tube wells, where water is pumped to the surface through a narrow tube, is that they are not prone to being contaminated.
But much of the surface water people are relying on has been contaminated, either by the bodies of dead livestock or - in coastal areas - by high salinity caused by the tidal surge that accompanied the storm.
The villagers in Tafalbari warn that many of them are suffering from diarrhoea.
"We need clean drinking water urgently. There is none here and we are having to drink dirty water from the river.
"It is very difficult for our children. They are really suffering," said distraught grandmother Zohanara through her tears.
These children are being looked after at a cyclone shelter
"We have nothing here, no home, hardly any food and no clean water. We are desperate."
The main fear among aid workers is that of water-borne diseases, chief of which is cholera.
However, in other recent natural disasters experienced by the people of Bangladesh - such as widespread flooding earlier this year - a cholera outbreak was not forthcoming.
A diarrhoea outbreak did happen, but then this is a country that is well used to tackling that problem. It pioneered oral rehydration therapy as a means of treating it.
Aid agencies and foreign donors say that they are addressing the water issue. Foreign countries and international donors have pledged around $500m so far for the relief effort.
"Support is being strengthened in nutrition, water, sanitation, hygiene and essential medicines," a UN spokesman in Dhaka told the BBC.
"These have been identified as the most vital needs according to assessment teams reporting back from the five main UN agencies in Bangladesh - including the World Food Programme and the UN Development Programme - from the worst affected areas."
The UN says that it has issued 7.3m water purification tablets (WPTs) and 110,000 jerry cans for carrying safe water in conjunction with the Bangladeshi Department of Public Health and Engineering.
"We have also ensured that an adequate stock of essential medicines is being delivered at districts and sub-districts in the worst affected areas," the spokesman said.
Evidence of this huge aid effort can now be seen on the ground, as can efforts by local NGOs to provide supplies.
But with winter on its way, there are also concerns that homeless people will also be vulnerable to cold weather.
According to the government, over a million houses were damaged by the cyclone, with at least 350,000 completely destroyed. Aid agencies say the real figure could be much more than that.
At last it looks as if the huge aid community that exists in Bangladesh is finally getting into full swing - but the big question now is whether or not its efforts will be in time.