|Group:||Group IV ((+)ssRNA)| Coronaviruses are a family of
enveloped, positive-stranded RNA viruses. The viral genome is
26–32 kb in length. Virions are spherical, 120–160 nm across
(Coronavirinae), bacilliform, 170–200 by 75–88 nm (Bafinivirus)
or found as a mixture of both, with bacilliform particles
characteristically bent into crescents (Torovirus). The
particles are typically decorated with large (~20 nm), club- or
petal-shaped surface projections (the “peplomers” or “spikes”),
which in electron micrographs of spherical particles create an
image reminiscent of the solar corona. The 5' and 3' ends of the
genome have a cap and poly (A) tract, respectively. The viral
envelope, obtained by budding through membranes of the ER and/or
Golgi apparatus, invariably contains two virus-specified
(glyco)protein species, S and M. Glycoprotein S comprises the
large surface projections, while the M protein is a triple-
spanning transmembrane protein. Toroviruses and a select subset
of coronaviruses (in particular the me