Coronaviruses are species in the genera of
virus belonging to one of two subfamilies
Coronavirinae and
Torovirinae in the family
Coronaviridae, in the order
Nidovirales. Coronaviruses are
enveloped viruses with a
positive-sense single-stranded
RNA genome and with a nucleocapsid of helical symmetry. The
genomic size of coronaviruses ranges from approximately 26 to 32 kilobases, the largest for an RNA virus.