The Ebola outbreak in West Africa is out of control and health-care workers should focus their efforts on stopping the spread of the virus, a senior director of Doctors Without Borders said Thursday.

"The situation is out of hand. The epidemic is not under control. And we don’t have enough response to fight it," Meinie Nicolai told CTV News in a Skype call from her home in Brussels.

Nicolai’s comments came the same day the World Health Organization raised the official Ebola death toll to over 1,500. The organization said there have been about 3,000 confirmed cases, but that the actual number of infections may be up to four times higher than the official tally.

At that rate, the WHO said the outbreak could reach up to 20,000 cases.

The most important step in addressing the outbreak should be stopping the spread of the disease, Nicolai said, rather than focusing on experimental treatments or cancelling international flights.

"To contain this epidemic will be the major, major challenge," Nicolai said. "It’s out of control. It’s still spreading to new areas."

The virus hasn’t even been controlled in the Guinnea town where Ebola first emerged, Nicolai said.

"Even that site is not under control. There’s still new infections happening there. So that’s six months, seven, eight months into the epidemic. That’s extremely worrying," she said.

Nicolai also said that Ebola’s presence in capital cities like Monrovia, Liberia, makes the spread of infection difficult to halt. Many capitals are difficult places to contain disease, as the cities have large populations that are highly mobile and live in close quarters.

In Monrovia, officials have tried to enforce curfews and quarantines to slow the spread of the disease. A Liberian slum with hundreds of residents was sealed off in an attempt halt infections, leading to food shortages and clashes with police.

On Thursday, the World Health Organization released a plan aimed at stopping transmission within six to nine months. The plan calls for more support for treatment and management centres, social mobilization, and safe burials.

Nicolai said the plan looks good on paper, but that its success relies on support from people and governments.

"Call on your government also to step up the response. We cannot sit and watch West Africa die. We have to do something," Nicolai said. "We should not just sit and wait cynically and wait until it comes to our countries. We have to help and step in."