page_title: Severe acute respiratory syndrome coronavirus 2
section_title: Phylogenetics and taxonomy
hierarchical_section_title: Severe acute respiratory syndrome coronavirus 2 / Virology / Phylogenetics and taxonomy
context_page_description: Severe acute respiratory syndrome coronavirus 2 is the strain of coronavirus that causes coronavirus disease 2019, the respiratory illness responsible for the COVID-19 pandemic. Colloquially known as simply the coronavirus, it was previously referred to by its provisional name, 2019 novel coronavirus, and has also been called human coronavirus 2019. The World Health Organization declared the outbreak a Public Health Emergency of International Concern on 30 January 2020, and a pandemic on 11 March 2020.
  SARS-CoV-2 is a Baltimore class IV positive-sense single-stranded RNA virus that is contagious in humans. As described by the U.S. National Institutes of Health, it is the successor to SARS-CoV-1, the strain that caused the 2002–2004 SARS outbreak.
  Taxonomically, SARS-CoV-2 is a strain of severe acute respiratory syndrome-related coronavirus. It is believed to have zoonotic origins and has close genetic similarity to bat coronaviruses, suggesting it emerged from a bat-borne virus. There is no evidence yet to link an intermediate animal reservoir, such as a pangolin, to its introduction to humans.
context_section_description: SARS-CoV-2 belongs to the broad family of viruses known as coronaviruses. It is a positive-sense single-stranded RNA (+ssRNA) virus, with a single linear RNA segment. Other coronaviruses are capable of causing illnesses ranging from the common cold to more severe diseases such as Middle East respiratory syndrome (MERS, fatality rate ~34%). It is the seventh known coronavirus to infect people, after 229E, NL63, OC43, HKU1, MERS-CoV, and the original SARS-CoV.
  Like the SARS-related coronavirus strain implicated in the 2003 SARS outbreak, SARS-CoV-2 is a member of the subgenus Sarbecovirus (beta-CoV lineage B). Its RNA sequence is approximately 30,000 bases in length. SARS-CoV-2 is unique among known betacoronaviruses in its incorporation of a polybasic cleavage site, a characteristic known to increase pathogenicity and transmissibility in other viruses.
  With a sufficient number of sequenced genomes, it is possible to reconstruct a phylogenetic tree of the mutation history of a family of viruses. By 12 January 2020, five genomes of SARS-CoV-2 had been isolated from Wuhan and reported by the Chinese Center for Disease Control and Prevention (CCDC) and other institutions; the number of genomes increased to 42 by 30 January 2020. A phylogenetic analysis of those samples showed they were "highly related with at most seven mutations relative to a common ancestor", implying that the first human infection occurred in November or December 2019. As of 7 May 2020, 4,690 SARS-CoV-2 genomes sampled on six continents were publicly available.
  On 11 February 2020, the International Committee on Taxonomy of Viruses announced that according to existing rules that compute hierarchical relationships among coronaviruses on the basis of five conserved sequences of nucleic acids, the differences between what was then called 2019-nCoV and the virus strain from the 2003 SARS outbreak were insufficient to make them separate viral species. Therefore, they identified 2019-nCoV as a strain of Severe acute respiratory syndrome-related coronavirus.
  In July 2020, scientists report that a more infectious SARS-CoV-2 variant with spike protein variant G614 has replaced D614 as the dominant form in the pandemic.
caption: Genomic organisation of isolate Wuhan-Hu-1, the earliest sequenced sample of SARS-CoV-2