CHICAGO (Reuters) - A common virus caused human adult stem cells to turn into fat cells and could explain why some people become obese, U.S. researchers said on Monday. The research builds on prior studies of adenovirus-36 -- a common cause of respiratory and eye infections -- and it may lead to an obesity vaccine, they said. "We're not talking about preventing all types of obesity, but if it is caused by this virus in humans, we want a vaccine to prevent this," said Nikhil Dhurandhar, an associate professor at Pennington Biomedical Research Center at Louisiana State University System. The...