section_path: Epidemiology/Background
section_name: Background
paragraph_text: Background
  
  SARS-CoV-2 is a virus closely related to bat coronaviruses, pangolin coronaviruses, and SARS-CoV. The first known outbreak (the 2019–2020 COVID-19 outbreak in mainland China) started in Wuhan, Hubei, China, in December 2019. Many early cases were linked to people who had visited the Huanan Seafood Wholesale Market there, but it is possible that human-to-human transmission began earlier. Molecular clock analysis suggests that the first cases were likely to have been between October and November 2019.
  
  The scientific consensus is that the virus is most likely of a zoonotic origin, from bats or another closely related mammal. While other explanations such as speculations that SARS-CoV-2 was accidentally released from a laboratory have been proposed, as of 2021 these were not supported by evidence.