A host double-stranded RNA-specific adenosine deaminase ADAR1 is induced by MeV infection, and U-to-C transition substitutions are introduced exclusively within the M gene, resulting in emergence of defective viruses, which cause subacute sclerosing panencephalitis (SSPE) [39]–[41]. The gene discussed is ADAR; the disease is subacute sclerosing panencephalitis.