Coronavirus - coronaviridae

Coronaviridae is a family of enveloped, positive-sense, single-stranded RNA viruses. The viral genome is 2632 kilobases in length. 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. Members of this family are thus referred to as coronaviruses. The newest addition is the 2019-nCoV, showing so far a lower mortality rate than the MERS- and SARS-coronavirus members.

Virology
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 endoplasmic reticulum (ER) and/or Golgi apparatus, invariably contains two virus-specified (glyco)protein species, S and M. Glycoprotein S comprises the large surface projections, while M is a triple-spanning transmembrane protein. Toroviruses and a select subset of coronaviruses (in particular the members of subgroup A in the genus Betacoronavirus) possess, in addition to the peplomers composed of S, a second type of surface projections composed of the hemagglutinin-esterase protein. Another important structural protein is the phosphoprotein N, which is responsible for the helical symmetry of the nucleocapsid that encloses the genomic RNA.