Cholera is the biggest worry - without treatment you can die in several hours. If cholera does not occur, it will be good luck, not good management.

"Digging a latrine for every 20 people and providing 20lts of water a day per person saves more lives than any of our fancy medical programmes. It's up there with measles vaccinations in terms of a priority but just has not been done", said Greg Elder who heads MSF's aid work in the region.

Well construction

"We have built about 20 wells in Darfur in the villages where the refuges have settled," according to Jan Heeger, Water and Sanitation advisor at the Holland office of MSF.

"In this emergency, the local people dig the hole about 3meters across the dig down until they reach the water table and then stop. That might be a few meters. Then we hire a local bricklayer to come in and he goes in the hole and builds a ring around the hole using locally fired bricks. This ring is about one meter high.

"When he finishes, the villages start digging again, deeper into the well and at some point the ring drops down under its own weight to the new, deeper level.

"At this stage we may return with a pump and empty the hole so they can dig further. This continues until the water fills the hole faster than the pump can empty it. By now the first ring has dropped to its lowest possible point.

"Then the bricklayer comes in a builds up the walls all the way to the top. There is a well head, about half a meter above the ground and an apron around it, 1.5 meters wide. In addition, there is drainage installed to waster water will not return to the well.

"The wells we are building in Darfur right now are open mouth versus pumps. With pumps, you can serve about 500 people. An open mouth means many people can access the water at the same time so you can serve about 1,000 people. It is about availability of water right now."

Around 1.2 million people are affected by the conflict between government troops and rebels in Darfur. Hundreds of thousands have been displaced - tens of thousands have fled to Mukjar, which used to have a population of 5,000. Workers from Medécins sans Frontierès (MSF) are digging wells and latrines to guard against the danger of epidemics that can break out when there are sudden concentrations of displaced people.

With the rainy season developing in Sudan, it will soon not be possible to build any more wells. The rain may fill wells and add to the water table, but can also bring unclean water supplies to areas relying on shallow water holes. Although there are heavy rains in some areas of Sudaan, it has not been everywhere. So there are still areas in Sudan where limited rains has allowed some well construction to continue. This will not last much longer.

This well, under construction at the end of July, measures just three metres across. Eight metres below, three men are working in the mud. One of them is Lucas Beck, logistics expert from MSF. With every well and latrine that he and his team complete, the danger of an epidemic among the refugees of Mukjar decreases slightly. In a few days, the new well will supply around a thousand people with clean drinking water - one thousand of the twenty thousand that are estimated to have found refuge in the small town.

Just a year ago, their home villages were attacked, looted and burnt down by militias loyal to the government. Nobody knows how many were killed in the raid, nor how many were injured or raped.

"Many have already moved on to larger towns like Zalingei or Nyala. The refugees feel safer there," explains Lucas Beck. "We look after the unhappy rest."

And they live in miserable conditions: up to ten people share one of the squalid bamboo shacks on the outskirts of Mukjar. Some have gotten plastic sheeting to put over the tent-like construction. The others are left with practically no shelter against the wind and sand, nor against the rains that started a few weeks ago.

A race against time

More and more patients are presenting symptoms of lung disease at the health centre set up by MSF in one of the empty buildings. Cases of malaria are also becoming more frequent - the puddles have become farms for the midges that carry the disease.

And the rainy season will bring a growth in the danger of diarrhoeal diseases. The rain washes mud and excrement into open wells and bore holes which people drink, unfiltered.

"It’s full of bacteria and pathogens," explains Lucas Beck, a water and sanitation expert. "In these conditions, the outbreak of diarrhoeal diseases such as cholera is only a matter of time."

Lucas Beck and his Sudanese colleagues hope to prevent this. They have already built so many wells and latrines that bricks have become scarce in Mukjar. At first, there were no spades in the village, which is 150 kilometres from the nearest tarmacked road.

"I got hold of a few old oil barrels and showed the village blacksmith how to make spades from them," recalled Beck, the Swiss logistics expert.

Construction kits for the crisis

The fight against the outbreak of diarrhoeal diseases is not yet won. But if cholera should break out - a highly infectious disease - treatment can begin within hours, as MSF have brought cholera kits to the neighbouring village: emergency construction kits that contain all the components of a fully-functioning cholera treatment centre. The tent with the isolation ward has already been put up.

The danger of epidemics is just one of many problems - but perhaps not the greatest.

"We can guard against diseases and treat them if necessary, and the people are less undernourished than in other areas of Darfur," explains the 30-year-old logistics expert. "But we are powerless against the unrestrained violence. That is very depressing."