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Three cases of Ebola have been confirmed in the U.S., but fear is spreading at a much faster pace, experts said.

Stevan Hobfall, a clinical psychologist at Chicago’s Rush University Medical Center, said that despite reassurances that a mass outbreak — like the one in West Africa — could not happen here, he is being peppered with questions about the deadly virus.

“A certain amount of anxiety is normal because this undermines our safety,” he said. “To seek information is rational; to be shutting oneself off at home is not.”

While he hasn’t had any patients on a self-imposed quarantine, there are some who have said they are avoiding public transportation and the movies.

He has tried to quell those fears by directing people to credible online sources, such as hospital websites, and recommending that they listen to science. For example, people cannot contract the disease from a sneeze 10 feet away or, as Centers for Disease Control and Prevention Director Tom Frieden explained at a media briefing this week, by sitting next to someone on a bus.

Ebola is spread through direct contact with bodily fluids of a sick person or exposure to objects such as needles that have been contaminated. The illness has an average eight- to 10-day incubation period, but it can be as many as 21 days, which is why the CDC recommends monitoring exposed people for symptoms for a full three weeks. People are not contagious during the incubation period, meaning before symptoms develop, such as a fever or vomiting.

Hobfall compared Ebola concerns to terrorism fears after 9/11. “At no time during the height of the (militancy) did it equal the death rate of traffic fatalities … but that’s not how fear works.”

The CDC is receiving up to 800 calls a day, the agency said.

On top of false alarms, Hobfall expected to see a spike of misinformation and conspiracy theorists claiming the government “knew about it or is hiding something,” he said.

Singer Chris Brown has already tweeted to his 13.7 million Twitter followers that the virus is intentional. “I think this Ebola epidemic is a form of population control,” he wrote.

Allison Ackerman, a clinical psychologist in Deerfield, said she also is fielding more questions from patients.

“They have all asked me about it and have done some reality testing by asking me if I am worried,” Ackerman said. “However, no one has admitted to an increase in compulsions designed to control the anxiety … but it is too soon to tell. I expect that more will come up in the coming week.”

About 3 million adults in the U.S. have obsessive-compulsive disorder, according to the International OCD Foundation, based in Boston. Some of the most common obsessions include contamination fears and are managed by excessive washing, cleaning and other such activities.

Gary Safron, 60, of Flossmoor, identifies as obsessive-compulsive and said he has struggled with irrational fears of illness since he was 18. He uses paper towels on bathroom doorknobs and never takes samples at the grocery store because “too many people with grubby hands” were there before him.

Still, he is not in panic mode about Ebola, he said. “But if I had been on a plane, I think this would be hitting me more. It would be causing more tension and racing thoughts.”

Patrick McGrath, a clinical psychologist and director of the Center for Anxiety and Obsessive Compulsive Disorders at Alexian Brothers Behavioral Health Hospital in Hoffman Estates, said calls started inching up with reports of the first case overseas — long before the first case surfaced in the U.S. last month. He is hearing about people canceling flights to Dallas and Atlanta and thinks that “it’s only a matter of time” that conventions will investigate moving to other cities.

“Anxious people live on maybes and what-ifs — not on truth and facts. We saw it with SARS … and we can expect to see it with Ebola too.”

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