At least 4,877 people have died in the world's worst recorded outbreak of Ebola, and at least 9,936 cases of the disease had been recorded as of 19 October.
However, the World Health Organization has said the true toll may be three times as much.
The WHO has said real numbers of cases are believed to be much higher than reported, while the death rate is thought to be about 70% of all cases.
That would suggest a toll of almost 15,000.
Liberia has been worst hit, with 4,665 recorded cases and 2,705 deaths, followed by Sierra Leone with 3,706 cases and 1,259 deaths.
Guinea, where the outbreak originated, has had 1,540 cases and 904 deaths.
In the past week, transmission of the disease was most intense in the capital cities of Monrovia and Freetown, while Guinea's capital Conakry reported 18 confirmed cases, its second highest weekly total since the outbreak began.
Although Ebola has been contained in Nigeria and Senegal, the disease is spreading towards Ivory Coast in both Liberia and Guinea, including in Guinea's Kankan district on a major trade route with Mali.
However, the WHO said the Liberian district of Lofa had seen a third consecutive week of decline in the number of cases, which reports from observers suggested was a result of disease control measures.
Among the thousands of cases are 443 health care workers, 244 of whom have died.
The WHO said it was undertaking extensive investigations to determine why so many had caught the disease.
"Early indications are that a substantial proportion of infections occurred outside the context of Ebola treatment and care," it said.
A UN plan to stop the epidemic involves isolating at least 70% of cases and safely burying at least 70% of those who die by 1 December, a 60-day deadline from the start of the plan.
That is supposed to rise to 100% by the 90-day deadline on 1 January.
The WHO estimates 28 laboratories are needed in the three worst-hit countries, with 12 now in place, and 20,000 staff will be needed to keep track of people who have had contact with Ebola patients and may be at risk.
The three worst-hit countries will also need 230 dead-body-management teams by 1 December, it said. They have 140.
The Ebola epidemic will take at least four months to contain even if all necessary steps are taken, the global head of the Red Cross said this morning, warning of "the price for inaction".
There is no licensed vaccine or cure for Ebola, which has also spread in several isolated cases among health workers in Spain and the United States.
Chronology - Worst Ebola outbreak on record
Meanwhile, a Liberian passenger who flew into New Jersey yesterday was taken to hospital over fears he had been exposed to Ebola, media reported.
The man, who had flown from Liberia to Brussels and then caught a connecting flight to Newark, had a fever, NBC New York reported, citing unnamed officials.
The passenger was "identified as reporting symptoms or having a potential exposure to Ebola," a spokeswoman for the US Centers for Disease Control and Prevention (CDC) told the network.
Three Ebola cases have been confirmed in the US: Liberian Thomas Eric Duncan, who died on 8 October at Texas Health Presbyterian Hospital in Dallas, and two nurses who treated him.
New measures were rolled out in the US this morning, which will see passengers arriving in the country from Ebola-hit Liberia, Sierra Leone and Guinea funnelled into five airports with extra health checks.
But experts writing in The Lancet yesterday said that screening air travellers on departure was a better option than monitoring them when they arrive abroad.
A plane carrying 51 Cuban doctors and nurses has arrived in Liberia to help treat victims of Ebola.
Another group of around 40 doctors from the communist-led Caribbean island were due to arrive in neighbouring Guinea today.
Cuba is sending the largest medical contingent to west Africa from any country in the world.
The US is sending 3,000 military engineers, medical personnel and other troops to the region to build Ebola Treatment Units and help train local medical staff to use them.
