The Ebola crisis in West Africa is a wide-ranging emergency that threatens to extend beyond the current regions of the outbreak, says the World Health Organization.

"This is a social crisis, a humanitarian crisis, an economic crisis, and a threat to national security well beyond the outbreak zones," WHO director general Margaret Chan told an emergency meeting of the UN Security Council on Thursday.

In some areas, such as Liberia's breadbasket region, hunger has become an even greater concern than the virus, Chan said.

The UN Security Council is meeting to decide if the Ebola outbreak is a global threat. Such a declaration could help push a co-ordinated strategy to handle the spread of the disease.

Elsewhere on Thursday, people in Sierra Leone were being told to stay inside for three days as part of a lockdown to control the Ebola outbreak, but a medical aid agency has warned the move could exacerbate the spread of the disease.

The World Health Organization said Thursday that more than 700 more Ebola cases emerged in West Africa in one week, which suggests the outbreak is accelerating. The Ebola virus has made more than 5,300 sick, mainly in Guinea, Sierra Leone and Liberia, and killed more than 2,600.

Liberian Red Cross health workers arrive to carry away the body of an Ebola victim at the JFK Ebola Treatment Center in Monrovia, Liberia, where about 1,000 more beds are needed, the World Health Organization says. (Zoom Dosso/AFP/Getty)

Sierra Leone’s government announced residents must stay home starting Thursday at midnight.

During the three-day measure, volunteers will go house to house to look for cases of Ebola with the aim of halting new infections and deliver information on the virus along with bars of soap.

"They will be going from house to house basically to be able to provide very clear message about Ebola and to be able to tell people what they should do within their family circle if they find that a particular member within the family is suffering from Ebola," said Steven Gaogia, co-ordinator of the emergency operation centre in Freetown.

Doctors Without Borders has warned that expertise is needed to conduct door-to-door screening and there’s a lack of Ebola treatment centres to manage potential patients who are identified.

"It has been our experience that lockdowns and quarantines do not help control Ebola as they end up driving people underground and jeopardizing the trust between people and health providers," the medical aid group said in a statement when the lockdown was proposed.

"This leads to the concealment of potential cases and ends up spreading the disease further."

Barry Andrews, chief executive of Irish aid agency Goal, also criticized the move.

"I'm not sure a public information campaign requires the draconian measure of three days locking six million people into

their homes," he said. "It puts terrible pressure on vulnerable people. People who live hand to mouth will find it difficult."

Last month in the West Point area of Liberia’s capital Monrovia, a riot erupted after the army arrived to enforce a quarantine.

Monrovia alone needs about 1,000 more beds, WHO said in noting that Liberia remains the worst affected country.

"Increases in demand for Ebola Treatment Centre (ETC) beds and referral unit places are continuing to outstrip capacity in Guinea, Liberia, and Sierra Leone," the UN health agency said in its update on Thursday.

Infected health-care workers

WHO called infections among health-care workers a "particularly alarming feature of this outbreak." So far, 318 health workers have developed Ebola virus disease and almost half have died. The workers focus on isolating and treating the sick and tracking the contacts of those who are infected to prevent further spread.

Elsewhere, Doctors Without Borders said it took two days to repatriate a female health-care worker to France from Liberia in a specially adapted U.S. aircraft. She's the aid group’s first international staff member to be infected.

"For a doctor, it's not acceptable to have people dying in front of you, to be unable to admit patients into quarantine centres because of a lack of international involvement, to ask bystanders to go back to their houses and risk them infecting those close to them, their families, their community," the group’s director for Belgium, Dr. Bertrand Degruez, told reporters in French.

"It's no longer acceptable to not have an airplane to reduce the time taken for medical evacuations."

The group’s operations director, Brice de la Vigne, said Doctors Without Borders has asked governments for a Medevac plane located in West Africa for such emergencies.

Earlier this week, U.S. President Barack Obama labelled Ebola a national security priority that demands fast action.