Biology and evolution of the coronavirus that causes COVID-19

ABSTRACT

The new coronavirus that causes COVID-19 is called SARS-CoV-2 and belongs to the subgenus Sarbecovirus, like its predecessor SARS-CoV. Bats appear to be the hosts of the ancestral viruses that originated these viruses, through recombination with the virus of an intermediate animal, which might be the pangolin. The virus interacts with the ACE2 receptor (angiotensin converting enzyme 2) and enters the cell by the endocytic pathway, through an early or late endosome. Viral RNA serves as messenger RNA for the translation of the first reading frame and the rest of the messenger RNAs are produced by discontinuous transcription. This peculiarity confers to this viral family a high frequency of recombination, which is associated to the high frequency of species jumping. Viruses belonging to the order Nidovirales are the only known RNA viruses with a polymerase with proof correction capacity;therefore their mutation rate is reduced. However, these genomes appear to be susceptible to be deaminated by cellular enzymes. All these mechanisms of generation of diversity leads to the existence of lineages, including those with the D614G mutation in the spike associated with a higher transmissibility. However, mutations associated with greater severity are not known to date. Just as there are different viral variants, the clinical manifestation of the disease is also highly variable. Some genetic, physiological and metabolic factors are being known that could be determining a more severe clinical presentations, often associated with the immunopathology of this disease.