Compounds, compositions and methods for preventing, treating or curing a coronavirus, picornavirus, and/or hepeviridae virus infection in human subjects or other animal hosts. Specific viruses that can be treated include enteroviruses. In one embodiment, the compounds can be used to treat an infection with a severe acute respiratory syndrome virus, such as human coronavirus 229E, SARS, MERS, SARS-CoV-1 (OC43), and SARS-CoV-2. In another embodiment, the methods are used to treat a patient co-infected with two or more of these viruses, or a combination of one or more of these viruses and norovirus.