![]() The most direct pathway of introduction is direct zoonotic transmission (also known as spillover) from the reservoir species to humans. These scenarios continue to be investigated to identify the definitive origin of the virus.ĭirect zoonotic transmission in a natural setting Each origin hypothesis attempts to explain this gap in virus evolution and location a different way. RaTG13 was sampled from bats in a mine in Mojiang County, Yunnan, located roughly 1,500 km (930 mi) away from Wuhan, and there are relatively few bat coronaviruses from Hubei province, where Wuhan is located. The earliest human cases of SARS-CoV-2 were identified in Wuhan, but the index case remains unknown. The evolutionary distance between SARS-CoV-2 and RaTG13 is estimated to be about 50 years (between 38 and 72 years). There is significant evidence and agreement that the most likely original viral reservoir for SARS-CoV-2 is horseshoe bats, with the closest known viral relatives being RaTG13 and BANAL-52, sampled from horseshoe bat droppings in Yunnan province in China and Feuang, Laos, respectively. There are multiple proposed explanations for how SARS-CoV-2 was introduced into, and evolved adaptations suited to, the human population. The origin of SARS-CoV-2 has been the subject of debate. In July 2023, a review article in The New York Times details information to date about the origins of the Covid-19 virus. 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. In response to the WHO's June 2022 report, Chinese Foreign Ministry spokesperson Zhao Lijian called the lab leak theory "a lie concocted by anti-China forces for political purposes, which has nothing to do with science". In July 2021, Zeng Yixin, Vice Health Minister of the Chinese National Health Commission, said that China would not participate in a second phase of investigation, denouncing the decision to proceed as "shocking" and "arrogant". In June 2022, a second round of investigations concluded that more investigations in the various possible pathways of emergence were necessary. WHO director-general Tedros Adhanom Ghebreyesus, in concert with various governments including the US and the EU, responded to the 2021 study report saying the matter still "requires further investigation". It also stated that a laboratory origin for the virus was "extremely unlikely". Echoing the assessment of most virologists, the study concluded that the virus most likely had a zoonotic origin in bats, possibly via an intermediate host. In 2021, the World Health Assembly (on behalf of the WHO) commissioned a study conducted jointly between WHO experts and Chinese scientists. As with the 2002–2004 SARS-CoV-1 outbreak, efforts to trace the specific geographic and taxonomic origins of SARS-CoV-2 could take years, and results may be inconclusive. Genomic sequence evidence indicates the spillover event introducing SARS-CoV-2 to humans likely occurred in late 2019. ![]() Research is ongoing as to whether SARS-CoV-2 came directly from bats or indirectly through an intermediate host, such as pangolins, civets, treeshrews, or raccoon dogs. ![]() SARS-CoV-2 has close genetic similarity to multiple previously identified bat coronaviruses, suggesting it crossed over into humans from bats. This theory is not supported by evidence. ![]() Some scientists and politicians have speculated that SARS-CoV-2 was accidentally released from a laboratory. Many other explanations, including several conspiracy theories, have been proposed. Most scientists agree that, as with many other pandemics in human history, the virus is likely derived from a bat-borne virus transmitted to humans via another animal in nature or during wildlife trade such at that in food markets. Since the beginning of the COVID-19 pandemic, there have been efforts by scientists, governments, and others to determine the origin of the SARS-CoV-2 virus.
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