'Living Drug' That Fights Cancer by Harnessing Immune System Clears Key Hurdle
From the article:   "Scientists use a virus to make the genetic changes in the T cells, raising fears about possible long-term side effects"

Is this a real risk? Is 'using a virus' in this way, still risky at all? or is it just the word 'virus' that makes writers put this line in every article about gene therapy?{edit: real risk}