The West Africa Ebola outbreak is an international public health emergency, the World Health Organization said.

After 2 days of teleconference, an emergency committee of experts agreed unanimously that the outbreak is an "extraordinary event" that poses a public health risk to states other than those already affected.

The consequences of further international spread would be "particularly serious" because of the virulence of the virus, the way it is spreading in communities and health facilities, and the "weak health systems in the currently affected and most at-risk countries," the agency said in a statement.

"The outbreak is moving faster than we can control it," WHO Director-General Margaret Chan, MD, said in a telephone media briefing.

She said the declaration of a public health emergency of international concern, as it's called under the International Health Regulations, "will galvanize the attention of leaders of all countries at the top level."

It will also "alert the world to the need for high vigilance," she said, "but by no means implies that all countries or even most countries will see Ebola cases."

A strong, coordinated international response is essential to stop the outbreak, Chan said, because "the countries affected simply do not have the ability to manage an outbreak of this size and complexity on their own."

The committee stopped short of calling for a general ban on travel to and from the affected region. But it emphasized that people with the disease and their contacts should not travel.

The outbreak started last December in Guinea and spread to neighboring Liberia and Sierra Leone. Nigeria is also reporting a handful of possible cases after a man flew from Liberia to Lagos in late July and died, apparently of Ebola.

The latest WHO figures show 1,779 cases and 961 deaths since the outbreak started.

At a congressional hearing Thursday, an official of a relief group that has been working in the region said the WHO figures probably only represent between 25% and 50% of the actual cases.

"This disease is uncontained and out of control in West Africa," according to Ken Isaacs of the Christian aid organization group Samaritan's Purse. A "broader international response is the only thing" that will slow it down, he said.

The governments of the affected countries, he said, "do not have the capacity" to handle the crisis.

At the same hearing, CDC Director Tom Frieden, MD, said tried and true containment measures will work to control the outbreak.

"We can stop Ebola," he said. "We know how to do it ... through tried and true means, the core public health interventions that work."

The interventions, he said, come down to three things -- finding active cases, treating them appropriately, and tracing their contacts.

"We have a difficult road ahead which will take many months," Frieden said, "but we must redouble our efforts to bring this terrible outbreak under control."

The extra efforts involved, the WHO committee said, include:

The affected countries should declare a national emergency, with the head of state addressing the nation to provide information.

They should also begin a "large-scale and sustained effort" to get local, religious, and traditional leaders and healers on their side.

They should ensure that "sufficient medical commodities, especially personal protective equipment," are available.

In some area of intense transmission, quarantine measures can be used to prevent movement.

So-called exit screening at airports, seaports, and major land crossings -- with at least a questionnaire and a temperature measurement -- should be used to find possible Ebola infections. People with an illness consistent with Ebola should only be allowed to travel if it is part of an appropriate medical evacuation.

Nearby countries that don't have Ebola transmission should begin to watch carefully for clusters of unexplained fever or deaths due to febrile illness, the committee urged. Finding such cases should be treated as a health emergency.

Additionally, they need to establish access to a diagnostic lab, make sure that health workers know how to employ infection prevention and control measures, and set up rapid response teams with the capacity to investigate and manage Ebola and contacts.

In the rest of the world, the WHO said, countries should provide travelers with relevant information on Ebola risks including ways to reduce risk and manage a potential exposure. They should also be prepared to detect, investigate, and manage Ebola cases.

Chan noted that the WHO is "extremely stretched" as it deals with four humanitarian crises, such as the war in Syria, and disease outbreaks including Ebola, and the Middle East coronavirus. Other international agencies, such as Doctors without Borders, are also under stress, she added.