A common virus that is harmless to people can destroy cancerous cells in the body and might be developed into a new cancer therapy, U.S. researchers said on Tuesday. The virus, called adeno-associated virus type 2, or AAV-2, infects an estimated 80 percent of the population. "Our results suggest that adeno-associated virus type 2, which infects the majority of the population but has no known ill effects, kills multiple types of cancer cells yet has no effect on healthy cells," said Craig Meyers, a professor of microbiology and immunology at the Penn State College of Medicine in Pennsylvania. "We believe...