The death toll from the Ebola epidemic has risen to 4,922 out of 10,141 recorded infections, with three West African countries accounting for most of the cases through October 23, the World Health Organization (WHO) said.
Guinea, Liberia and Sierra Leone have reported 4,912 deaths out of 10,114 cases, the WHO said in its update on Saturday.
The virus, which reached Mali through a two-year-old girl who died on Friday, now also threatens Ivory Coast, having infected people virtually all along its borders with Guinea and Liberia, the United Nations agency said.
Ivory Coast is the world's biggest cocoa producer, and the outbreak has hurt the economic growth that has been raising living standards in the region.
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The overall figures include outbreaks in Nigeria and Senegal, deemed by the WHO to be now over, as well as isolated cases in Spain, the United States and a single case in Mali.
But the true toll may be three times as much: by a factor of 1.5 in Guinea, 2 in Sierra Leone and 2.5 in Liberia, while the death rate is thought to be about 70 percent of all cases.
The WHO has said that many families are keeping infected people at home rather than putting them into isolation in treatment centres, some of which have refused patients due to a lack of beds and basic supplies.
The UN agency, sounding an ominous note, said that out of the eight districts of Liberia and Guinea sharing a border with Ivory Coast, only two have yet to report confirmed or probable Ebola cases.
The WHO said 15 African states including Ivory Coast are at highest risk of the deadly virus being imported.
In an interview with Al Jazeera, Dr. Celine Gounder, an infection diseases specialist in New York said, Ebola cases continue to rise exponentially.
"Unfortunately, the world's response has been too little, too slow, too late," she said, calling for more doctors and treatment facilities to West Africa to help control the spread of the infection.
No border closure in Mali
On Saturday, Mali's President Ibrahim Boubacar Keita said his country will not close its border with Guinea, even after the first reported Ebola death in the land-locked country.
"Guinea is Mali's neighbour. We have a shared border that we did not close and we will not close," he said.
Keita said that health workers have already traced the journey of the infected two-year-old girl and her grandmother, who travelled on public transport from Guinea.
The girl travelled hundreds of kilometres through Mali by bus - including a stop in the capital Bamako - potentially exposing many people to the virus, before she died in the western town of Kayes on Friday.
Keita said that the girl's grandmother had made a mistake by going to a funeral in Guinea, where more than 900 people have died of Ebola, and bringing her back.
"We are paying dearly for this," he said. "But I think this will cause more fear than anything else. The case was quickly contained. We will do everything we can to avoid panic," he told France's RFI radio station.
Mali relies on the ports of neighbouring Senegal, Guinea and Ivory Coast as gateways for much of its import needs.
Local and international Ebola experts are sending teams to Mali to try to contain the outbreak in the sixth West African nation to record Ebola this year.
The World Health Organization said 43 people who came into contact with the child, including 10 health workers, were being monitored for symptoms and held in isolation.