Methods and compositions are provided for modulating, e.g., reducing, viral coding sequence expression in mammals and mammalian cells. In the subject methods, an effective amount of an RNAi agent, e.g., an interfering ribonucleic acid (such as an siRNA or shRNA) or a transcription template thereof, e.g., a DNA encoding an shRNA, is introduced into a target cell, e.g., by being administered to a mammal that includes the target cell, e.g., via a hydrodynamic administration protocol. Also provided are RNAi agent pharmaceutical preparations for use in the subject methods. The subject methods and compositions find use in a variety of different applications, including academic and therapeutic applications.