The World Health Organization (WHO) has reported 21 new deaths of Ebola in West African countries in just three days this week.
"The epidemic trend in Liberia and Sierra Leone remains precarious with high numbers of new cases and deaths being reported between July 6 and 8,” the WHO said in a statement issued on Thursday.
Regional leaders believe it is now a race against time to control the epidemic and prevent it from spreading to other countries.
They have agreed to set up a fund to contain the outbreak. At a summit of the Economic Community of West African States (ECOWAS) in Ghana on Thursday, Nigerian President Goodluck Jonathan pledged to contribute $3 million to the fund.
Earlier, the WHO had stated that neighboring countries should take the necessary precautions to protect their citizens from the deadly disease.
So far, the UN health agency has put the death toll from Ebola at 539 in West Africa since the outbreak began in Guinea in February.
Guinea is the worst-hit country with 409 cases and 309 deaths.
Liberia has so far reported 142 cases and 88 deaths, while 142 have lost their lives in Sierra Leone among 337 reported cases.
There is currently no known cure for Ebola, a form of hemorrhagic fever whose symptoms are diarrhea, vomiting and bleeding.
The virus spreads through direct contact with infected blood, feces or sweat. It can also be spread through sexual contact or the unprotected handling of contaminated corpses.
Ebola was first discovered in the Democratic Republic of Congo in 1976 in an outbreak that killed 280 people.
It remains one of the world’s most virulent diseases, which kills between 25 to 90 percent of those who fall sick.