FREETOWN - High numbers of new cases of the Ebola virus are being reported in Sierra Leone and Liberia, with 19 deaths over three days this week, the UN's World Health Organization (WHO) says.
Such figures showed that it was a race against time to control the epidemic in Sierra Leone, medical charity MSF said.
In total there have been 539 deaths in West Africa since the outbreak began in neighbouring Guinea in February.
Regional leaders have now agreed to set up a fund to combat its spread.
At a summit of the regional body Ecowas in Ghana on Thursday, Nigeria's President Goodluck Jonathan agreed to contribute $3m (£1.8m) to the fund.
Ebola spreads through contact with an infected person's bodily fluids and there is no vaccine or cure.
It kills up to 90% of those infected but if patients receive early treatment, they have a better chance of survival.
'Precarious'
The WHO statement said that Sierra Leone had accounted for 32 new cases and 15 deaths, while Liberia reported 11 new cases and four deaths.