The Ebola outbreak in West Africa is an international public health emergency that demands an extraordinary response, the World Health Organization declared Friday.

The outbreak has killed at least 961 people as of Aug. 6 and "is moving faster than we can control it," WHO’s director general Margaret Chan told reporters from Geneva.

"The possible consequences of further international spread are particularly serious in view of the virulence of the virus," the UN health agency said in a statement.

The affected countries of Guinea, Liberia, Sierra Leone and Nigeria don’t have the capacity to manage an outbreak of this size and complexity they are facing, Chan said in urging the international community to provide support.

The decision by WHO’s emergency committee, which includes Dr. Theresa Tam from the Public Health Agency of Canada, was unanimous.

The declaration shows WHO is taking the outbreak seriously, but more means needs to be done, said the aid group Doctors Without Borders — known by its French initials, MSF.

"We welcome today's declaration by the WHO," said Jonathan Jennings, deputy director of MSF Canada in Toronto. "We very much think, though, that it needs to be translated into action on the ground."

More medical teams, epidemiologists, case detection and infection-control specialists need to deployed immediately in the field to halt the spread of the disease, Jennings said.

The UN health agency said all states with Ebola transmission should declare a national emergency, as Nigeria did Friday.

The declaration of a global health emergency means travel restrictions can be imposed, but Chan said that for now, there shouldn’t be a general ban on international travel or trade. Countries should still be prepared to detect, investigate and manage Ebola cases, she said.

"The likelihood is that things will get worse before they get better," added WHO’s head of health security, Keiji Fukuda.

The WHO said that efforts to contain the outbreak have been hampered by inexperience and misconceptions about the threat, such as how it spreads.

'Drop everything and get a handle on this'

Jonathan Epstein is a veterinary epidemiologist based in New York and associate vice-president of the EcoHealth Alliance, a group of scientists researching the relationships between wildlife, ecosystems and human health to limit the spread of diseases from animals to people.

Epstein said that coupled with moves by governments in West Africa to set up quarantine areas and to continue to provide hospital services, there needs to be more effective educational outreach.

"I think something that could be effective is having people who survive infection become ambassadors to help communicate that supportive care is really important," Epstein said.

Since there are no licensed drugs or vaccines for the viral disease, patients are offered supportive care for symptoms such as vomiting and diarrhea that can lead to severe dehydration.

Dr. Michael Gardam, director of infection prevention and control at Toronto's University Health Network, appreciated WHO's recommendations to the affected countries.

"Usually, Ebola virus outbreaks burn themselves out fairly quickly and they're done. This has not burned itself out. It keeps expanding and at some point, what you would have done in the past is not enough. You have to do more and that's where this declaration is very helpful in really pushing people to now drop everything and get a handle on this."

There are a number of challenges in the affected countries, said Dr. Kamran Khan of the infectious disease division at St. Michael's Hospital in Toronto. In a hospital video, Khan said these include:

Cultural practices around cleansing bodies before burial that put people into contact with the virus.

Lack of health-care resources to trace contacts of Ebola patients and monitor them for the full 21-day incubation period.

Public distrust of health authorities in some circumstances.

Earlier this week, Liberia and Sierra Leone brought in troops to enforce quarantines and to bar infected people from travelling and spreading the infection.