The failure of Sierra Leone's strategy for fighting Ebola may be down to a missing ingredient: a big shock that could change people's behaviour and finally prevent further infection.

Bruce Aylward, the head of Ebola response at the World Health Organisation, said Sierra Leone was well placed to contain the disease — its worst outbreak on record — with infrastructure, organization and aid.

The problem is that its people have yet to be shocked out of behaviour that is helping the disease to spread, still keeping infected loved ones close and touching the bodies of the dead.

"Every new place that gets infected goes through that same terrible learning curve where a lot of people have to die … before those behaviours start to change," Aylward told Reuters.

While neighbouring Liberia has turned the tide of Ebola, and both Mali and Nigeria quickly smothered outbreaks, Sierra Leone has more than 70 per cent of cases reported in the past three weeks and more than half the 18,000 confirmed cases in the nine-month-old outbreak.

The WHO's death toll from outbreak has climbed to 6,583 but the actual figure is likely to be far higher due to under-reporting of cases.

The flare-up in Sierra Leone's capital Freetown and the country's more heavily populated western areas resemble the massive infections suffered in August by Liberia's capital Monrovia.

That country got its infection rates under control after panic in quarantined areas led to a riot and the shooting of a young boy by security forces. Scenes of people dying in the street raised alarm across the country and prompted a military deployment by the United States to build treatment centres.

"In Monrovia you had bodies on the streets, you had a riot, you had someone shot — awareness went through the roof in a very, very short time as a result," said Aylward.

"You don't want to see that kind of thing drive public awareness but it has an impact very, very fast. People changed behaviours in Monrovia — bang! Like that."

Mali also learned through a shock. Just as it seemed nobody had been infected by its first Ebola patient in October, another cluster of deaths sprang up the following month. Aylward said he told Malian officials that the only way to stop the outbreak was to trace anyone who may be at risk.

"That's when the contact tracing... took a jump from around 60-70 percent completion to 98 percent," he said.

Learning curve to change behaviour

Denial and ignorance are part of the problem but a weak healthcare system and logistics also play a part. Officials in Kono — where an explosion of infections was discovered this week — said the eastern district of 350,000 inhabitants had only one ambulance and no Ebola treatment centre.

WHO staff are visiting neighbouring West African countries to try to get people to change their ways in case Ebola strikes, but worry there has been little change in remote border areas, Aylward said.

"The forest area of these three countries has got some really special and concerning practices, where they share meals with the corpse, where they sleep with the corpse," he said.

"You know these are high, high risk behaviours."

In Sierra Leone, where as many as 365 Ebola deaths may have been linked to a single traditional funeral early in the epidemic, Sierra Leone's Health Minister Abu Bakarr Fofanah said the government was considering banning some unsafe practices.

He recognized however that it would be difficult to police such a law.

Fofanah noted that some areas of eastern Sierra Leone that were hit hardest early in the epidemic — around the towns of Kenema and Kailahun — have seen a massive reduction in case numbers as people change behaviour.

"The areas that are now doing badly are the areas that were affected last. They are still on the learning curve."