FREETOWN, Sierra Leone (AP) — Shoppers crowded streets and markets in Sierra Leone's capital on Thursday stocking up for a three-day shutdown that authorities will hope will slow the spread of the Ebola outbreak that is accelerating across West Africa.

The Ebola outbreak sweeping West Africa has also touched Liberia, Guinea, Nigeria and Senegal, and is believed to have sickened more than 5,300, according to figures released by the World Health Organization on Thursday. In a sign that the outbreak is picking up steam, more than 700 of those cases were recorded in the last week for which data is available.

The disease is now estimated to have killed more than 2,600 people; most deaths have been in Liberia. But the World Health Organization has said that the official toll is probably a gross underestimate and that most patients are at home — and infecting others in the community — not in treatment centers.

The U.N. Security Council will discuss the Ebola threat later Thursday.

Starting Thursday at midnight, Sierra Leone's 6 million people must stay home, except for thousands of volunteers who will go house-to-house delivering bars of soap and information about how to prevent Ebola. Authorities have said they also expect to discover hundreds of new cases during the Friday, Saturday and Sunday exercise.

Many people during this outbreak have not sought treatment for Ebola out of fear that hospitals are merely places people go to die. Still others have been turned away by centers overwhelmed by the increasing number of patients.

Sierra Leone's government says it has prepared screening and treatment centers to accept the expected influx of patients after the shutdown.

As shoppers rushed to buy last-minute items, some merchants worried about how they would feed their own families after losing three days' worth of income. Much of Sierra Leone's population lives on $2 a day or less, and making ends meet is a day-to-day struggle.

"If we do not sell here we cannot eat," said Isatu Sesay, a vegetable seller in a market in the capital's central business district. "We do not know how we will survive during the three-day shutdown."

The spiraling outbreak is overwhelming the resources deployed to fight it. Sierra Leone and Liberia have only about 20 percent of the beds they need to treat patients. The Liberian capital of Monrovia alone needs about 1,000 more beds, the World Health Organization said Thursday.

In recent weeks, several countries have promised to build treatment centers, send health care workers and deliver supplies. In one of the largest offers of aid so far, the United States plans to send 3,000 military personnel to the region and build more than a dozen treatment centers in Liberia. Maj. Gen. Darryl Williams has already arrived in Monrovia to set up a command center for the operation and survey sites for the clinics, defense officials said.

Ebola is spread through the bodily fluids of those who have symptoms or of the dead. That puts health workers at a particularly high risk, and they have paid a heavy price in this outbreak. Some 318 have become infected, with about half of them dying.

A French nurse for Doctors Without Borders who became infected in Liberia was being flown to Paris on Thursday. The woman, who first showed symptoms on Tuesday, was conscious and being taken to a hospital prepared to treat Ebola patients.

With no licensed treatment for Ebola, public health experts have kept the focus on isolating the sick and tracking down anyone those infected have come into contact with. In past outbreaks, stopping the chain of transmission has been crucial to defeating the disease, but the current outbreak has ballooned out of control, leading to more stringent measures including travel restrictions, the cordoning off of entire communities and now Sierra Leone's nation-wide lockdown.

Confusion and fear about the disease and anger over some of these measures has occasionally sparked unrest. In Guinea this week, a team that was doing disinfection and education on prevention methods was attacked. A group of young people set upon the team in a village in the country's southeast, the epicenter of the disease, and they have been missing since, a local government official said.

Though there is no recognized treatment for Ebola, doctors have been testing out experimental ones in this outbreak. For instance, some patients have been given the blood of Ebola survivors, a measure some scientists think can help patients fight off the virus.

British nurse William Pooley, who was infected while working in Sierra Leone and has since recovered, has flown to the United States to donate his blood to an American patient, according to the Foreign Office. It was not disclosed which American patient would be receiving blood from Pooley. Two Americans are currently being treated for Ebola in the U.S.

Doctors said Wednesday that one of them, aid worker Rick Sacra, who is being treated in Nebraska, is now expected to make a full recovery. The other, a WHO doctor, has not been identified.

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Cheng reported from London. Associated Press writers Lolita Baldor in Washington, Sarah DiLorenzo in Dakar, Senegal, Nicolas Garriga in Paris and Boubacar Diallo in Conakry, Guinea, contributed to this report.