Abstract In 2019, a new human pandemic coronavirus (SARS-CoV-2) emerged in Wuhan, China. We present the knowledge about SARS-CoV-2 compared to SARS-CoV and MERS-CoV. The SARS-CoV-2 is similar to other coronaviruses, nevertheless, differences were observed. Cell entry of SARS-CoV-2 is facilitated by cleavage of spike protein by furin. The receptor-binding motif of SARS-CoV-2 spike protein forms a larger binding interface and more contacts with host receptor ACE2 compared those of in SARS-CoV. Unlike other coronaviruses, the SARS-CoV-2 spike protein has a motif, known to bind integrins. Nucleocapsid protein and RNA-dependent RNA polymerase of SARS-CoV-2 display some structural differences compared to those of SARS-CoV as well. These features may increase the efficiency of the spread of SARS-CoV-2 and indicate the putative targets for specific antiviral therapy. 1. Taxonomy of Coronaviridae. 2. Structure of Betacoronavirus virion. 3. Genome of Betacoronavirus. 4. Proteins of Betacoronavirus. 5. Betacoronavirus replication cycle. 6. Pathogenesis of SARS-CoV-2. 6.1. Tissue and cellular pathogenesis. 6.2. Molecular basis of pathogenesis. 6.3. Immunopathological changes in COVID-19. 7. Conclusions