Avigan (favipiravir) has been developed as an anti-influenza drug and is attracting attention as an anti-COVID-19 drug, because Avigan has exhibited therapeutic efficacy against new coronavirus (COVID-19) infections. This article reviews the development of Avigan as an anti-influenza drug, its mode of action as an anti-RNA-dependent RNA polymerase drug, toxicity to embryogenesis and teratogenicity, and its activity to COVID-19. The epidemic of the new coronavirus infection began, and masks, hand washing, and self-restraint were continued to prevent it. As a result, infection control measures have had the effect of reducing the epidemics of various infectious diseases except for some. This seems to be important information for implementing transplantation medicine.
