Dr. Ian Mohr, a virologist at New York University, altered the herpes virus so that it isn't attacked by the immune system and kills cancer cells more efficiently.
Another virus that is proving effective for liver cancer is Vaccinia. Vaccinia is used to protect against smallpox and so far the results have been promising. Several groups of patients have had an increase in survival times. Meanwhile other viruses are being used for things like melanoma, bladder cancer, and head and neck cancer.