Coronaviruses are a group of common, ancient, and diverse viruses. They infect many mammalian and avian species and cause respiratory, gastrointestinal and central nervous system diseases. Coronavirus virions contain an envelope, a helical capsid, and single-stranded and positive-sense RNA genome. The length of their genomes, which are the largest among all RNA viruses, typically ranges between 27 and 32 kb.  They were named “coronaviruses” because the protruding spike proteins on their envelope that give the virions a crown-like shape (“corona” in Latin means crown).