New York, N.Y. -- A man who visited West Africa last month and is at a New York City hospital being tested for possible Ebola likely doesn't have it, according to a report from The Associated Press.
A doctor at Mount Sinai Medical Center in Manhattan says "odds are" it's not Ebola. Dr. Jeremy Boal says he hopes for a definitive answer in the next day or two.
The hospital says the patient had a high fever and gastrointestinal symptoms when he went in Monday. It placed him in isolation.
The Ebola virus causes a hemorrhagic fever that has sickened more than 1,600 people, killing nearly 900 mostly in Liberia, Guinea and Sierra Leone.
A spokesman for the Centers for Disease Control and Prevention says at least three Americans have been tested in the U.S and all tested negative.
The World Health Organization announced Monday that the death toll has increased from 729 to 887 deaths in Guinea, Sierra Leone, Liberia and Nigeria, CBS News reported. Most of the newly reported deaths occurred in Liberia.
Officials in Liberia have ordered the remains of victims to be cremated to prevent further infection.
As CBS News' Omar Villafranca reported, the WHO reported there are now as many as 1,600 cases of Ebola in West Africa in total.
A group of Americans was set to head to Africa Monday to fight the deadly disease.
"I think of it this way — I think that if we have a dangerous war going on at a distant shore, our soldiers don't say, 'Hey, we're scared, we're not going to go,'" said Dr. Nahid Bhadelia of Boston University Medical School, one of the Americans going.
American doctor Kent Brantly, who contracted the virus in Liberia, was said to be making progress Monday. He arrived at Emory University Hospital in Atlanta on Saturday, and wearing a full protective suit, he surprised doctors walking into his specially-designed isolated treatment room.
PHOTOS: American doctor with Ebola taken to Atlanta hospital
"The fact that he's able to walk into the hospital is a very, very good sign," said Dr. Anthony Fauci of the National Institute of Health.
Brantly's fellow infected aid worker, Nancy Writebol, was expected to leave Liberia and arrive at Emory's isolation unit Tuesday.
"The room is really designed to provide ICU-level care for critically ill patients, as well as have a surrounding infrastructure that really contains any potential pathogens," said Dr. Jay Varkey of Emory University Hospital.
Both Writebol and Brantly have received doses of an experimental serum, but doctors have not said if the serum is helping.
Meanwhile, the Centers for Disease Control and Prevention said last week that it will evaluate any travelers with signs of dangerous infectious diseases and isolate them when necessary.
U.S. health officials last week also warned Americans not to travel to the three West African countries hit by the outbreak of Ebola.
The purpose of the travel warning is to not only protect U.S. travelers, but limit their use of overburdened clinics and hospitals for injuries or other illnesses, he said.
The current outbreak is the largest since the disease first emerged in Africa nearly 40 years ago.
The virus is contagious and is spread by direct contact with blood or bodily fluids from a sick person. Ebola can't be spread like flu through casual contact or breathing in the same air.
There is no cure or vaccine for Ebola, but a vaccine is set to begin human trials next month. So far, the vaccine has shown success in monkeys.
For more information on Ebola from the CDC, click here.
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