SARS-CoV-2 infection mechanism. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19). The virus spike proteins (blue), attach to receptors for angiotensin converting enzyme 2 (ACE2, brown) on human cells. Initial spike protein priming by transmembrane protease, serine 2 (TMPRSS2, pink) allows the fusion of the viral membrane with the cell membrane. Alternatively, the virus enters the cell through endocytosis. The virion then releases its genetic material, ribonucleic acid (RNA, red), and hijacks the cell's machinery to produce copies of viral RNA and viral proteins. These are assembled into new virions in the Golgi apparatus, and released from the host cell, ready to infect further cells.