Doug Stanglin

USA TODAY

The U.S. Centers for Disease Control and Prevention has issued its highest-level alert for a response to the Ebola crisis in West Africa.

"Ops Center moved to Level 1 response to given the extension to Nigeria & potential to affect many lives," CDC chief Tom Frieden said Wednesday on Twitter.

Level 1 means that increased staff and resources will be devoted to the outbreak, officials said. It is the first time the agency has invoked its highest level alert since 2009, over a flu outbreak.

Meantime, a Nigerian nurse who had treated the country's first fatality from Ebola two weeks ago has died from the virus that has now claimed more than 900 lives in the latest outbreak, Nigerian health officials said.

The World Health Organization, which convened a two-day emergency meeting of global health workers to discuss the crisis in Guinea, Liberia, Nigeria and Sierra Leone, said Wednesday that the death toll had jumped to 932, an increase of 45 fatalities in just four days.

Next week, the WHO will convene a panel of medical ethicists to explore the use of experimental treatment in the latest outbreak in West Africa.

In a statement on Wednesday, the WHO noted that the recent use of experimental drugs to treat two American medical missionaries has raised questions on whether drugs that have never been tested on humans should be used and, if so, who should receive it when there is only an extremely limited amount.

The two Americans, Kent Brantly and Nancy Writebol, have been repatriated from Liberia and are being treated for Ebola at the Emory University Hospital in Atlanta.

In New York, Mount Sinai Hospital said a patient placed in isolation since Monday does not have an Ebola infection, as feared. The patient is in stable condition and "improving," a statement from the hospital said.

In Nigeria, health officials said five other Nigerian health workers who also had treated American Patrick Sawyer have been diagnosed with the disease. Sawyer, a financial expert of Liberian descent who lives in Minnesota, died July 25 after arriving in Lagos on a flight from Liberia.

Meanwhile, a Saudi man being tested for the disease has died in Jeddah after returning from Sierra Leone on Sunday, according to Saudi health authorities.

If the Saudi death is found to be linked to the Ebola virus, it would be the first fatality outside the four West African countries during the latest outbreak, the Saudi Health Ministry says.

In Liberia late Wednesday, President Ellen Johnson Sirleaf declared a state of emergency because of the Ebola outbreak, saying some civil rights may have to be suspended as a result of the crisis. At least 282 people in Liberia have died from the disease.

In her televised speech, Sirleaf said that "ignorance and poverty, as well as entrenched religious and cultural practices, continue to exacerbate the spread of the disease."

Earlier, Nigerian health minister, Onyebuchi Chukwu, speaking to reporters in the capital, Abuja, confirmed the death of the Nigerian nurse on Tuesday and said the five newly diagnosed cases are being treated at an isolation ward in Lagos, The Guardian reports.

Lagos health officials also acknowledged that Sawyer was not initially isolated after becoming ill because authorities did not know immediately that he had contracted the Ebola virus.

There is no known cure for Ebola. Experts say people infected with the virus can spread the disease only through their bodily fluids and after they show symptoms. Since the incubation period can last up to three weeks, some of the Nigerians who treated Sawyer are only now showing signs of illness that can mimic many common tropical illnesses — fever, muscle aches and vomiting.

In April, Saudi Arabia said it would not issue visas this year to Muslim pilgrims from Sierra Leone, Liberia and Guinea during the hajj pilgrimage to Mecca.

Saudi Ambassador in Guinea Amjad Bedaiwi was quoted in the Saudi Arab News Wednesday as saying the decision affects a total of 7,400 pilgrims from those three countries.

Meanwhile, Spain was sending a specially equipped plane to Liberia to pick up a 75-year-old Spanish missionary priest, Miguel Pajares, and two nuns who have tested positive for the virus.

The three had worked at St. Joseph's Catholic hospital, which was shut down following the death last week from Ebola of Patrick Nshamdze, the hospital's director. Three other hospital staff members have been diagnosed with the disease.

In Washington, President Obama pledged international support for the countries affected by the Ebola outbreak in remarks at the U.S.-Africa summit.

"The United States and our international partners will continue to do whatever we can to help our African partners respond to this crisis and stand with the people of Guinea, Liberia and Sierra Leone," he said.

Contributing: Associated Press

Following Doug Stanglin on Twitter: @dstanglin