Hyperthermia increases expression of the antiviral cellular factors APOBEC3A and APOBEC3G and induces G-to-A or C-to-T mutations in human papilloma virus cervical cell lines and genital warts. This unexpected effect of heat treatment correlated with regression of genital warts in a subset of patients, including at distant sites, suggesting that this effect may be mediated in part by antiviral as well as immunological mechanisms.