Coronaviruses were recognized as a group of enveloped, RNA viruses in 1968 and accepted by the International Committee on the Taxonomy of Viruses as a separate family, the Coronaviridae, in 1975. By 1978, it had become evident that the coronavirus genomic RNA was infectious (i. e., positive strand), and by 1983, at least the framework of the coronavirus replication strategy had been per- ceived. Subsequently, with the application of recombinant DNA techniques, there have been remarkable advances in our understanding of the molecular biology of coronaviruses, and a mass of structural data...