The deadly Ebola epidemic engulfing three West African countries is "out of control," health experts at the Council on Foreign Relations said Tuesday.

The virus, which has claimed almost 900 lives since March, hasn't "ever been in control" since Ebola was first discovered in 1976, said Laurie Garrett, CFR's senior fellow for global health. 

Garrett spoke on a conference call with reporters as the second American infected with Ebola in Africa arrived in Atlanta for treatment under strict quarantine, and a day after a patient in New York City was tested for the disease. City health authorities concluded the patient is unlikely to have Ebola.

“There is no strategic plan of how we’re going to bring this under control,” Garrett said. “What will be the global strategy if this disease shows up elsewhere?”

The Centers for Disease Control and Prevention are sending 50 medical professionals to Guinea, Liberia and Sierra Leone in the next few days to relieve and assist people working on the crisis, Garrett said.

The World Bank on Monday pledged $200 million in emergency funding to help the West African nations contain the spread of infections and help their communities fight the deadly disease, which has historically reached fatality rates of 90%.

The money will help pay for medical supplies, salaries for medical staff and materials needed to stabilize health systems, the bank said in a statement. The financing comes after requests from the World Health Organization and officials from Guinea, Liberia and Sierra Leone.

There is no vaccine or cure for Ebola, which is spread only by direct contact with bodily fluids. The virus causes high fever and bleeding from all orifices. Many patients die from dehydration.

More than 550 healthcare workers are struggling to stem the epidemic in West Africa, including some from nonprofit groups in the U.S. and Europe. In many areas, local authorities distrust the aid workers, and have accused them of spreading the disease.

Some aid workers have issued pleas, saying they’re exhausted and terrified, and they’re living in a state of fear, even of siege. More than 60 healthcare workers have died fighting the outbreak.

If the outbreak is marked as a global health crisis, African countries would have to strengthen border checks and other measures to stop the spread of the disease. Vaccine development probably would increase.

WHO has been running on a budget deficit, Garrett said, and such emergency responses have been cut or limited to smaller groups, such as Samaritan’s Purse, SIM and Catholic Relief Services.

John Campbell, CFR senior fellow for Africa policy studies and former U.S. ambassador to Nigeria, said Ebola has already had an impact on the economies in the West African nations. Sierra Leone’s growth rate has been cut by 1%, Campbell said, and more dramatic economic and political consequences are possible.

The three countries affected are going through an extremely rapid period of urbanization, Campbell said. Liberia and Sierra Leone are emerging from lengthy civil wars, and rural villagers are packing into urban slums, making quarantine difficult.

If the epidemic spreads into Lagos, Nigeria’s largest city and the second-fastest growing city in Africa, it will have “destabilizing consequences,” Campbell said.

The city of 22 million has recorded two cases of Ebola so far, and eight people have been put in quarantine since the cases were confirmed, a Nigerian health minister said Tuesday.

While taking simple precautions can prevent Ebola, the outbreak has reignited fear of a global pandemic. Many other diseases, though not as deadly, can spread quickly if international systems aren’t put in place now.

“When Ebola burns out, it could be replaced by something else,” Campbell said.