Coxsackievirus A21 (CVA21) is a naturally occurring virus, that is known to cause self limiting upper respiratory infections. CVA21 has been shown in cell culture to infect and kill human melanoma cancer cell lines. This property of CVA21 is due to the specific receptors CVA21 uses in order to attach to, and infect a cell. The 2 receptors CVA21 uses to infect a cell are Intracellular Adhesion Molecule 1 (ICAM-1) and Decay Accelerating Factor. Both of these surface proteins are expressed on melanoma cell lines as well as human melanoma tumours. Animal models of human melanoma tumours have demonstrated that CVA21 injection either intratumour or intravenous causes infection in the tumours, resulting in reduction of tumour size and growth.