Volume 5, Issue 2, December 2010
WOO, Patrick CY
Professor, Department of Microbiology, The University of Hong Kong
Coronavirus study group, International Committee for Taxonomy of Viruses
The Coronaviridae family is classified into two subfamilies, Coronavirinae and Torovirinae. Members of the Coronavirinae subfamily are in general referred to as coronaviruses. Phenotypically, coronaviruses are enveloped viruses of 120-160 nm in diameter. Under electronmicroscopy, coronaviruses have a crown-like appearance and the name “coronavirus” is derived from the Greek word κορώνα, which means crown. Genotypically, coronaviruses are positive-sense, single-stranded RNA viruses with genome sizes of about 30 kb, the largest genome size among all RNA viruses. Traditionally, coronaviruses were classified into three groups based on their antigenic relationships. Groups 1 and 2 are madeup of mammalian coronaviruses and group 3 aviancoronaviruses. Recently, the Coronavirus Study Group of the International Committee for Taxonomy of Viruses (ICTV) has proposed three genera, Alphacoronavirus, Betacoronavirus and Gammacoronavirus, to replace these threetraditional groups of coronaviruses. Before 2003, there were less than 10 coronaviruses with complete genomes available, with only two human coronaviruses, namely human coronavirus 229E (HCoV-229E) and human coronavirus OC43 (HCoV-OC43), which were discovered in the 1960s. The SARS epidemic in 2003 has boosted interest in coronavirus research globally; and most notably, in the discovery of novel coronaviruses and their genomics. In the past six years, our group has discovered 13 novel coronaviruses, including one novel human coronavirus [human coronavirus HKU1 (HCoV-HKU1)], SARS-related Rhinolophus batcoronavirus (SARSr-Rh-BatCoV), eight other bat coronaviruses and three avian coronaviruses, and has sequenced the genomes of nine of them(1-5). Others have also discovered additional coronaviruses, the most notable being human coronavirus NL63 (HCoV-NL63), discovered by a group in the Netherlands (6).