Geneva - The rate of new Ebola infections appears to be slowing in hard-hit Liberia, but the crisis is far from over, the World Health Organisation said on Wednesday.
"It appears that the trend is real in Liberia and there may indeed be a slowing of the epidemic there," WHO assistant director-general Bruce Aylward told reporters in Geneva.
"There is increasing evidence that these countries can get on top of this," he said.
Aylward added, though, that he was "terrified that the information will be misinterpreted and that people will begin to think Ebola is under control".
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"That is like thinking your pet tiger is under control," he warned, pointing out that the deadly outbreak had seemed to slow previously only to come back with more virulence.
The Ebola outbreak that has been ravaging west Africa has claimed 4 922 lives, according to the latest update from the WHO. The vast majority of the deaths were in Liberia, Guinea and Sierra Leone.
Controversy over quarantine measures
Washington meanwhile ordered a 21-day quarantine for all US troops returning from west Africa, as controversy raged over the US government's attempts to prevent the spread of Ebola.
The move exposed a split between the US military and other government agencies, with civilian health workers subjected to less strict measures than American soldiers.
President Barack Obama hailed "heroic" US health workers battling Ebola, seeking to reassure the public amid the controversy over quarantine measures imposed by some authorities including the Pentagon.
Speaking at the White House after meeting with returned health workers including Kent Brantly, an American doctor infected with the often-deadly disease in Liberia, Obama said those who volunteer on the front lines "deserve our gratitude, and they deserve to be treated with dignity and with respect. "
He defended the "sensible, scientific" guidelines set out by the US Centres for Disease Control and Prevention on Monday.
The CDC has urged active monitoring of those at risk, meaning they must be checked for fever daily for 21 days and must restrict their travel and public activities for the duration of the virus's incubation period.
13 703 Ebola cases
Aylward said that the number of Ebola cases had soared to 13 703 - up from just over 10 000 the WHO reported on Saturday - but he stressed that the increase was mainly due to previously unreported cases being added to the statistics.
Liberia counted 6 535 cases, Sierra Leone had 5 235 and Guinea, where the outbreak began late last year, counted 1 906, he said.
Neighbouring Mali, where a two-year-old girl died from Ebola following a long bus ride from Guinea, had not yet detected any new infections, he added.
Aylward said data from a range of different sources - including from funeral directors and from treatment centres reporting lower Ebola patient admission rates - indicated a "downward trend" across much of Liberia.
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A number of beds at Ebola treatment centres in the country were now empty, he said.
A rapid scaling up of information to the community about the deadly virus, contact tracing and implementation of safe burial practices had likely contributed to the positive trend seen in Liberia, Aylward said.
His cautious optimism on the situation in Liberia came a day after Obama and the Red Cross offered hope that progress was being made in the battle against the killer virus.
Obama insisted the disease "will be defeated". He also stressed that science, not fear, should guide the response to the virus.
US quarantines troops
There has been growing condemnation of Washington's rush to quarantine people who have come into contact with those suffering from Ebola, amid fears such strict measures could dissuade much-needed healthcare workers and others from travelling to the affected region.
Only two people have been infected with the virus on US soil, and both have been declared cured.
Nonetheless, California announced a new 21-day quarantine for anyone travelling from Ebola-afflicted countries who has had contact with someone infected with the disease. The move comes after similar measures were adopted in New Jersey and New York.
Also on Wednesday, Pentagon chief Chuck Hagel ordered a three-week quarantine for all US troops returning from west Africa, calling it a "prudent" measure to prevent the spread of the virus.
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Hagel said the measure was adopted partly because military families urged the quarantine.
There are now about 1 100 US troops in Liberia and Senegal, with plans to boost the force to as many as 4 000 soldiers.
Meanwhile, the WHO said its main priority was still to increase the number of treatment centres in west Africa.
Anthony Banbury, the head of the United Nations Mission for Ebola Emergency Response (UNMEER), said more than 50 treatment centres were needed but only 33 had been set up.
The mission also faces challenges in deciding where to deploy its limited resources, he said at the office's Accra headquarters.
"We have to make sure though that the beds are placed at the right locations and that depends on good information on exactly where the disease is," Banbury said.