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Ebola worries are growing in the United States, but there are reasons people should feel safe.ThinkStock

A doctor who cared for the first Ebola patients in the United States says the virus is unlikely to spread. In fact, hospital officials can't even find the Ebola virus on surfaces in the patients' rooms.

"We have rather intense nursing, which is critical," said Bruce Ribner, professor of medicine at Emory University Hospital in Atlanta, which has already taken two American Ebola patients who were infected in West Africa. "We found no virus on surfaces in the room, even in the bathroom or around the bed. Contrast that with West Africa, where there is gross pollution of the entire patient environment."

How Ebola and Other Viruses Mutate

Ribner made his remarks Thursday to reporters from a meeting of the Infectious Disease Society of America in Philadelphia. He said that there are several reasons why Ebola won't spread here.

1. The virus is not airborne, and there's no evidence that it will get that way. While the current epidemic in West Africa is the most widespread since Ebola was identified in the 1970s, the route of transmission is still through bodily fluids like blood, sweat, urine or vomit. That means you have to have very close contact with an infected person to get the virus. While some people may fear a mutation that will turn it airborne, that scenario would likely happen first in West Africa, Ribner said.

2. Patients who become infected are not contagious until they are seriously ill, making it much more difficult to spread while traveling, for example.

Officials at the CDC are monitoring people who traveled on the same plane as Thomas Eric Duncan, the Liberian man who contracted Ebola and died Wednesday at a Dallas hospital. So far, none of the other passengers have shown any symptoms.

3. U.S. health officials say they are making a huge effort at tracing down everyone who had contact with Duncan and any of the other Ebola patients, such as the freelance NBC cameraman who tested positive for Ebola in Liberia and was brought to a Nebraska hospital last week.

4. All the U.S. patients and members of Duncan's family have been isolated from the rest of the community for 21 days, the time that it takes Ebola to make a person ill.

How Can Ebola Be Stopped?

"You may have one generation of spread," said Jeff Duchin, chief epidemiologist for Seattle and King County, Wash., "but once they are under observation, it shouldn't spread to anyone else at that point."

Duchin said he understands the fear that many people, and some healthcare workers, are feeling right now. It's because Ebola is new to the United States and everyone is learning how to deal with it.

"It's a scary disease with a high fatality rate," Duchin told Discovery News. "But the good news is the spread can be contained with simple measures: early identification, contact tracing, isolation and good infectious disease control measures."

Duchin noted that several Ebola patients traveled from the infected nations into neighboring Nigeria in recent months, sparking fears of a widening of the outbreak. But that nation's public health system was able to shut down the disease before it spread.