evidence: On 31 December 2019, the Wuhan Municipal Health Commission reported an outbreak of pneumonia on its official website. Subsequently, scientists reported the discovery of a previously undescribed coronavirus obtained from samples of the respiratory system of some of these patients. This virus differed from all known coronaviruses including severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) and Middle East respiratory syndrome (MERS) coronavirus (MERS-CoV)1,2,3,4,5. The World Health Organization (WHO) named the disease coronavirus disease 2019 (COVID-19) and the International Committee on Taxonomy of Viruses named this new infectious agent SARS-CoV-2 (ref. 6); the seventh coronavirus that can infect humans. SARS-CoV-2 rapidly spread through the globally, producing several variants of concern (VOCs) and developing into a major and devastating pandemic. Here we summarize our current understanding of the emergence, global spread and genetic diversity of SARS-CoV-2.