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Virotherapy, the use of oncolytic viruses for cancer therapy, is an old con-cept currently making substantial clinical progress. Oncolytic viruses, whose tumor selectivity is genetically engineered or naturally occurring, replicate in and kill cancer cells but not normal tissue, and thus have the potential to amplify them-selves in situ and spread throughout the tumor (Fig. 1). Immunovirotherapy takes advantage of the natural inflammatory responses to virus infection and immune responses to oncolytic virus-induced cancer cell death to drive therapeutic anti-tumor immunity and thus act as i