"It could happen," said Dr. Susan Gerber, a medical epidemiologist in the CDC's Division of Viral Diseases.

"That's why the CDC is working closely with the World Health Organization and other international partners."

Spread

WHO has asked member states to keep an eye out for severe acute respiratory infections and review them for unusual patterns.

It did not recommend travel or trade restrictions for countries where the virus has been found.

Dr. Susan Gerber, a medical epidemiologist in the CDC's Division of Viral Diseases, agrees.

There's no evidence of sustained human-to-human transmission, she said, "where you see a chain of many cases going person to person to person."

"People shouldn't freak out," she added. "There's no evidence that this virus is easily spread, say, across a room."