Geneva - The UN's Ebola czar on Tuesday hailed widespread progress in the fight against the deadly virus, but warned the outbreak was still surging in western Sierra Leone and northern Guinea.
"We know the outbreak is still flaming strongly in western Sierra Leone and some parts of the interior of Guinea," David Nabarro, the UN coordinator on Ebola, told reporters in Geneva.
He said more foreign health workers and specialists were needed in the areas where the disease was still spreading quickly, as were more treatment units and beds.
"We can't rest," he said, insisting on the need to "maintain global attention and vigilance".
The worst ever Ebola outbreak has left more than 6,300 people dead worldwide, nearly all in Sierra Leone, Guinea and Liberia.
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On Monday, the World Health Organization published new figures showing that the number of cases in Sierra Leone for the first time had overtaken the number in Liberia, long the hardest-hit country.
Sierra Leone now counts 7,798 cases, 1,742 of them fatal, compared with 7,719 in Liberia, including 3,177 deaths.
In Guinea, where the outbreak started in December last year, 1,412 people have died out of 2,283 cases, according to the latest tally.
WHO set a 60-day goal on October 1 to isolate 70 percent of Ebola patients in Liberia, Guinea and Sierra Leone and ensure safe burials for 70 percent of bodies, which are highly infectious.
The UN health agency said last week that Liberia and Guinea had met both targets, while Sierra Leone had met the target on safe burials.
"We're moving towards the treatment target in Sierra Leone," Nabarro said, adding that several hundred more beds were set to become available within the next few weeks.
The surge in transmission rates in the west of the country, including in the capital Freetown, was linked to the fact that the community there had not been as quick to embrace recommended behaviour changes needed to slow the spread of the virus, Nabarro said.
Especially in the more urban areas, it was more difficult for those infected to isolate themselves.
Nabarro hailed both the global and national responses to the outbreak, highlighting a the sharp drop in transmission rates in Liberia.
But he warned: "We can't sit back and say the job is even partially done because... as long as there is infection in a part of an area that could easily spread, it could even spread to places where current infections levels are zero.
"Every day we wake up and we realise the enormity of the job that still lies ahead."