A compound or a pharmaceutically acceptable salt or composition thereof for the treatment of a host infected with or exposed to a virus of theParamyxoviridaeorOrthomyxoviridaefamily, or other disorders, in particular respiratory syncytial virus, more fully described herein.本文提供一種用於治療宿主之化合物或其醫藥學上可接受之鹽或組合物,該宿主係感染或暴露於副黏液病毒科或正黏液病毒科或其他病症之病毒、尤其是本文中更充分描述的呼吸道融合細胞病毒。