A ribonucleoside with broad-spectrum antiviral activity; reduces the number of viral plaques in BHK-21 cells infected with dengue type 2, reovirus type 1, West Nile, and yellow fever RNA viruses (EC50s = 95, 26, 80, and 75 μM, respectively); inhibits HCV replication (EC50 = 2.2 μM in a replicon assay); protects MDBK cells from BVDV and HCoV infection (EC50s = 2.2 and 90 μM, respectively); reduces infectious virus yield in BHK-21 cells infected with FMDV and SVDV (EC50s = 6.4 and 45.2 μM, respectively); reduces viral shedding to undetectable levels in a mouse model of persistent norovirus infection