COVID-19 lab leak theory

The COVID-19 lab leak theory, or lab leak hypothesis, is the idea that SARS-CoV-2, the virus that caused the COVID-19 pandemic, came from a laboratory. This claim is highly controversial; most scientists believe the virus spilled into human populations through natural zoonosis (transfer directly from an infected non-human animal), similar to the SARS-CoV-1 and MERS-CoV outbreaks, and consistent with other pandemics in human history.^[1] Available evidence suggests that the SARS-CoV-2 virus was originally harbored by bats, and spread to humans from infected wild animals, functioning as an intermediate host, at the Huanan Seafood Market in Wuhan, Hubei, China, in December 2019.^[5][6] Several candidate animal species have been identified as potential intermediate hosts.^[13] There is no evidence SARS-CoV-2 existed in any laboratory prior to the pandemic,^[14][15][16] or that any suspicious biosecurity incidents happened in any laboratory.^[17]

Many scenarios proposed for a lab leak are characteristic of conspiracy theories.^[18] Central to many is the misplaced suspicion about the proximity of the outbreak to a virology institute that studies coronaviruses, the Wuhan Institute of Virology (WIV). Most large Chinese cities have laboratories that study coronaviruses,^[14][19] and virus outbreaks typically begin in rural areas, but are first noticed in large cities.^[20] If a coronavirus outbreak occurs in China, there is a high likelihood it will occur near a large city, and therefore near a laboratory studying coronaviruses.^[20][21] The idea of a leak at the WIV also gained support due to secrecy during the Chinese government's response.^[14][22] The lab leak theory and its weaponization by politicians have both leveraged and increased anti-Chinese racism.^[23] Scientists from WIV had previously collected virus samples from bats in the wild, and allegations that they also performed undisclosed work on such viruses are central to some versions of the idea.^[24] Some versions, particularly those alleging genome engineering, are based on misinformation or misrepresentations of scientific evidence.^[25][26][27]

The idea that the virus was released from a laboratory (accidentally or deliberately) appeared early in the pandemic.^[28][29] It gained popularity in the United States through promotion by conservative personalities in early 2020,^[30] fomenting tensions between the U.S. and China.^[31] Scientists and media outlets widely dismissed it as a conspiracy theory.^[32][33] The accidental leak idea had a resurgence in 2021.^[34] In March, the World Health Organization (WHO) published a report which deemed the possibility "extremely unlikely", though the WHO's director-general said the report's conclusions were not definitive.^[35] Subsequent plans for laboratory audits were rejected by China.^[22][36]

Most scientists remain skeptical of the possibility of a laboratory origin, citing a lack of any supporting evidence for a lab leak and the abundant evidence supporting zoonosis.^[15][37] Though some scientists agree a lab leak should be examined as part of ongoing investigations,^[38][39] politicization remains a concern.^[40][41] In July 2022, two papers published in Science described novel epidemiological and genetic evidence that suggested the pandemic likely began at the Huanan Seafood Wholesale Market and did not come from a laboratory.^[16][42][5]