The present invention is directed to compounds, compositions and methods for treating or preventing cancer and viral infections, in particular, HIV, HCV, Norovirus, Saporovirus, cytomegalovirus (CMV), herpes viruses (HSV-1, HSV-2), Dengue virus, Yellow fever, or HBV in human patients or other animal hosts. The compounds are certain N4-hydroxycytidine nucleosides derivatives, modified monophosphate and phosphonates prodrugs analogs, and pharmaceutically acceptable, salts, prodrugs, and other derivatives thereof. In particular, the compounds show potent antiviral activity against HIV-1, HIV-2, HCV, Norovirus, Saporovirus, cytomegalovirus (CMV), herpes viruses (HSV-1, HSV-2), Dengue virus, Yellow fever, and HBV.
