Viral culprits may explain a host of tumors with as-yet unknown triggers- Science News

As of now, the official figure for the percentage of human cancers caused by viruses is around 20 percent — but most experts concede that number is largely an educated guess, accounting for known viruses behaving in predictable ways. “Thirty years ago, that number would have been 5 percent,” says Robert Garry, a virologist at Tulane University School of Medicine in New Orleans. “It’s a moving target. How high is it going to go? We don’t know.”