KOUREMALE, Mali - At a Mali border post in Kouremale about 130 km (80 miles) south of the capital Bamako, five health workers stand under a thatched roof, directing passengers arriving from Guinea to wash their hands.

Their temperatures are then taken with digital guns to check for fever, one of the early symptoms of the deadly Ebola virus that originated in Guinea and has spread to its southern neighbors Sierra Leone and Liberia.

Mali is the only country that has not closed its border with Guinea. For regional health officials, this has narrowed the risk of potentially infected people slipping through in to Mali. So far, no case of Ebola has been recorded in Mali.

But the operation at the border post to keep Ebola out poses logistical challenges at this remote point in the West African scrubland. The hand-washing water has to be trucked in from a village 15 km (nine miles) away in steel barrels and there is a lack of chairs in the waiting area.

The main difficulty for Mali to keep the disease out, however, is that is that many travellers simply avoid the official border crossing - the lone paved road connecting the two West African countries - altogether.

"There are many cars that pass by clandestine roads because they are scared of the controls," said Djibril Bassole, a public transport driver plying the route from Conakry to the Malian capital Bamako.

One kilometre north of the Kouremale crossing is a depot for cars coming from the Guinean capital that have sneaked in through a side road and avoided the Ebola control checkpoint.

GOLD MINING HUB

Mali has deployed gendarmes along the border to track people's movements, but the border's porosity means that it is impossible to trace everyone.

"There are the official borders but of course people live and travel from one side to another," said Xavier Crespin, director of the West African Health Organization who led a delegation checking on Mali's border preparations.

The region is an artisanal gold mining hub that attracts workers from throughout northern Guinea and southern Mali. Guinean workers often enter Mali in the day and go home to Guinea at night.

"If Ebola comes to Mali it won't be by the road, it will come through the mining areas," said Kone Diahara Traore, the border region's health officer.

Mali's health ministry has relied thus far on effective controls at the official borders and strong community networks elsewhere, telling villagers to stay vigilant and report any suspected Ebola cases immediately.

Besides gendarmes, the local governments have also set up community anti-Ebola brigades, Traore said. "They say that they are more scared than we are because Guineans eat with them every day," she said.

But ensuring the border is Ebola-free remains a major challenge.

"The people who pass without going through the checkpoints are poorly educated. If they were aware that you are fighting this virus, they would go and get checked," said Moussa Keita, a Malian gold miner who walks across the border to Guinea every morning to go to work.

"I saw someone getting into a fight when someone tried to check (his temperature). Not everyone understands," Keita said.

The Ebola outbreak, the worst on record, has killed 3,439 people and infected some 7,492, with cases reported in Nigeria, Senegal and the United States.

To keep the disease out, several countries have banned travel and flights to and from Ebola-affected countries, while some neighbours have shut their borders.