This has been known for a while and been discussed in depth in my genetics, cancer bio and cell culture classes. The problem with using a virus to kill cancer is that it needs to be genetically engineered to be highly lethal upon infection and have a very high transfer rate. This is because cancer cells divide very quickly and the virus need to be able to keep up.
The problem arises in that viruses are prone to mutations. If such a deadly virus was to mutate so that it no longer only targeted cancer cells, then you would have a highly contagious and deadly virus out in the wild. It could lead to the greatest plague mankind has ever known.
The definitive evidence that video games turn people into mass murderers
