We’re 23 of the 27 authentic members of the Scientific Advisory Group for the Origins of Novel Pathogens (SAGO) for the World Well being Group (WHO). After almost 3.5 years of deliberations, we concluded our unbiased evaluation of the origin of the coronavirus SARS-CoV-2, and supplied our report1 in June 2025 to the WHO director-general.
Meet the scientists investigating the origins of the COVID pandemic
Within the 78-page doc, we decided that a lot of the peer-reviewed scientific proof helps the speculation that SARS-CoV-2 has a zoonotic origin, which means that it got here from an animal. However till requests for extra data are met or extra knowledge develop into obtainable, there could be no certainty about when, the place and the way SARS-CoV-2 entered the human inhabitants.
Though the time period of the primary SAGO group led to October final yr, which means we’re not members, the WHO has proposed a second time period for SAGO and issued a name for brand spanking new members. Our 2025 report1 supplies suggestions for subsequent investigations looking for to ascertain the origin of the COVID-19 pandemic. Within the meantime, with the politicization and hypothesis across the origin of the pandemic displaying no indicators of abating, 23 of us mark the shut of SAGO’s first chapter by clarifying our place on the origin of SARS-CoV-2 and the science behind it in a extra accessible approach.
Of the 4 authentic members of SAGO who usually are not co-authors of this text, one resigned earlier than the 2025 report was finalized. Three others dissented from our choice to guage the likelihood that SARS-CoV-2 had leaked from a laboratory on the premise of there being no proof for this (see hypotheses three and 4 beneath). We’re grateful to all 4 for his or her contributions to our investigation. Certainly one of us (M.G.G.), whose identify is on the 2025 report, requests that her dissent concerning the analysis of the lab-leak hypotheses be famous.
We stress that we’re solely accountable for the views expressed on this article, and that such views don’t essentially characterize the views, choices or insurance policies of the WHO, or of any establishments that we’re affiliated with.
Mission-driven
The WHO’s director-general, Tedros Adhanom Ghebreyesus, established SAGO in November 2021 and tasked it with designing a guiding framework to steer two issues: an ongoing effort to attempt to decide the origins of SARS-CoV-2, and investigations of how rising and re-emerging pathogens originate extra broadly2.
The 27 unbiased scientific specialists from 27 international locations who made up SAGO investigated all cheap prospects — not with the purpose of blaming anybody nation for the emergence of SARS-CoV-2, however to find out what occurred in order that the world is healthier in a position to forestall epidemics and pandemics sooner or later.
To analyze the origin of SARS-CoV-2 within the human inhabitants, we assessed experiences of early circumstances and medical research. We investigated potential sources of an infection, together with animal reservoirs, intermediate hosts, insect vectors and environmental sources. We additionally assessed the genomics and evolutionary biology of the virus, in addition to the potential for the virus having escaped by means of a lab or research-associated incident. These key ‘checkpoints’ are listed within the world framework doc that we revealed in 20243.
A nurse and affected person at a short lived COVID-19 ward exterior a hospital in Los Angeles, California, in 2021.Credit score: Francine Orr/Los Angeles Instances by way of Getty
Our deliberations on the origins of SARS-CoV-2 have been based mostly on the obtainable scientific proof. We used the work of worldwide groups4 that in 2020 and 2021 had visited Wuhan, China, the place the primary evidence-backed circumstances of the virus circulating in people have been found5. We used revealed scientific research related to all of the areas we have been investigating; preprints and displays by scientists who had labored on related analysis, both in China or elsewhere; and discussions involving worldwide specialists and SAGO members held between November 2021 and June 2025. We additionally consulted opinions performed by numerous scientific our bodies, together with a 2022 Lancet Fee6. And we reviewed publicly obtainable intelligence experiences from oversight committees and authorities companies, as summarized in our 2025 publication1.
4 scientifically credible hypotheses had been proposed earlier than November 2021 by the Joint WHO–China Research, an effort to quickly inform China and the world on subsequent steps within the response to the outbreak. Right here, we summarize our conclusions following our investigations into the plausibility of every.
Speculation one: animals contaminated with SARS-CoV-2 handed the virus to people
Many of the peer-reviewed scientific proof helps this speculation.
Though they’re too distantly associated to SARS-CoV-2 to have been its direct progenitors, intently associated ancestral strains have been present in horseshoe bats (Rhinolophus spp.) in southeast Asia. A Betacoronavirus known as RaTG13, which shares 96.1% of its genetic code with SARS-CoV-2, was recognized in 2013 in China7. (Betacoronavirus is the genus to which SARS-CoV-2 belongs.) One other pressure known as BANAL-52, which shares 96.8% of its genetic code with SARS-CoV-2, was recognized in 2020 in Laos8. This implies that comparable strains circulating in bats in China or southeast Asia may need spilled over to intermediate animal hosts or on to people.
Why the world wants extra transparency on the origins of novel pathogens
We additionally know that the Huanan Seafood Market in Wuhan had a major position within the early transmission and preliminary unfold of the virus.
Greater than 60% of the identified earliest human circumstances in December 2019 concerned individuals who labored on the market, made purchases there, lived close to it or had another epidemiological hyperlink with it9. (At the least 175 folks have been recognized with the illness, both by means of lab testing or on the premise of medical signs earlier than 1 January 2020.)
Two distinct genetic lineages of SARS-CoV-2 have been recognized in samples from early circumstances related to the Huanan market, in addition to from the environmental sampling of stalls and run-off water in drains on the market in January 2020. This helps the concept the virus had already been evolving in animals earlier than it reached the market10.
Raccoon canines (Nyctereutes procyonoides) are vulnerable to early strains of SARS-CoV-2.Credit score: Getty
Metagenomic sequencing of environmental samples collected on the market has indicated that a number of wildlife species had been there earlier than it was cleaned and sterilized on 1 January 2020 by the Chinese language authorities in response to the outbreak. These embody raccoon canines (Nyctereutes procyonoides), hoary bamboo rats (Rhizomys pruinosus) and palm civets (Paguma larvata), all of that are identified to be vulnerable to the early strains of SARS-CoV-211,12. These animals may have been the intermediate hosts that introduced the virus to the market, resulting in the early circumstances in people11,12 — though it stays unclear whether or not the virus first contaminated people at Huanan, or whether or not the spillover occasion occurred earlier, with the virus subsequently being carried to the market by contaminated people or animals.
Including to all this, there is no such thing as a verified proof of the existence of human or animal circumstances of SARS-CoV-2 an infection anyplace else earlier than December 2019. There have been retrospective experiences of 1 or two doable circumstances occurring in November 2019 in Italy and France, and of the virus being detected in a wastewater pattern (additionally in November that yr) in Brazil. However in all situations, the optimistic take a look at outcomes couldn’t be confirmed by unbiased labs.
Speculation two: SARS-CoV-2 was launched into China’s animal markets from abroad by means of imported items
The 2021 WHO–China Joint Research and SAGO’s 2022 report each decided that additional knowledge could be required to assist this concept4,5.
In April final yr, the Chinese language authorities endorsed this route because the almost definitely supply of SARS-CoV-2. However nearly six years on from the beginning of the pandemic, we conclude that the obtainable scientific proof doesn’t assist this speculation1.
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SARS-CoV-2 was detected on frozen items, however solely a number of months into the pandemic when the virus was already widespread in people. By this level, contaminated folks may have contaminated surfaces. Additionally, no additional proof has develop into obtainable to counsel that the transmission of SARS-CoV-2 to people from frozen merchandise occurred at Huanan Seafood Market, at every other market in Wuhan or elsewhere initially of the pandemic.
Speculation three: SARS-CoV-2 originated from an unintended lab-related occasion
A lot of the data wanted to evaluate this speculation has not been made obtainable to the WHO or SAGO.
Repeated requests have been made to the Chinese language authorities by the WHO to launch the well being data of research-lab workers, biosafety and biosecurity protocols, and audits or unbiased inspections performed to confirm the protection procedures of labs in Wuhan. These embody these of the Chinese language Middle for Illness Management and Prevention in Wuhan and the Wuhan Institute of Virology, a number one analysis centre for bat coronaviruses. In our view, the federal government has not supplied the required data that we’ve requested for the reason that launch of SAGO in November 2021 to analyze a possible biosafety breach. The Nationwide Well being Fee of China states that the nation has shared all related knowledge and data, and proposes that investigations be undertaken as an alternative in labs in different international locations the place coronavirus analysis has been performed13.
A chicken market in Hong Kong in 2025.Credit score: Yau Ming Low/Shutterstock
Many of the scientific opinions we assessed assist the zoonotic-origins speculation and discover no conclusive proof for a lab leak. Many of the revealed government-agency and intelligence experiences that we assessed (that are listed in our 2025 publication1) assign ranges of confidence, equivalent to ‘low’ or ‘average’, to the lab-leak or zoonotic-origins hypotheses. However such experiences ship totally different conclusions, seemingly on the premise of political slightly than scientific arguments.
In brief, revealed intelligence experiences, which focus primarily on biosafety and biosecurity insurance policies and practices on the Wuhan Institute of Virology, are speculative. None supplies concrete proof of a breach.
Collectively, these experiences spotlight the continued want for an intensive, unbiased investigation into the origins of SARS-CoV-2 to boost world well being safety. SAGO and the WHO have requested further intelligence experiences, together with those who have been labeled or unpublished on the time, which a number of international locations have produced in current months — together with China, Germany and the US. This data has not but been supplied to SAGO or to the general public.
Speculation 4: SARS-CoV-2 originated from the deliberate manipulation of a virus in a lab
We analysed experiences on the genome construction of SARS-CoV-2, in addition to publications addressing the chance that it had been manipulated by means of reverse genetics. This entails making alterations to a virus’s identified genes or regulatory parts to analyze how focused mutations change its properties. Such modifications could be launched to make a virus much less pathogenic, as an illustration, or simpler to check.
We didn’t discover proof to counsel that SARS-CoV-2 ensuing from experimental manipulation was a extra possible state of affairs than it rising from naturally occurring mutations or recombination occasions. (Recombination entails the alternate of genetic materials between genetically distinct, however normally intently associated, viruses that infect the identical host cell.)
Members of Sarbecovirus, the viral subgenus of the Betacoronavirus genus to which SARS-CoV-2, SARS-CoV-1 and different SARS-related coronaviruses (primarily from bats) belong, have mosaic genomes. Items of the viruses’ genomes originate from distinct evolutionary lineages owing to a number of recombination occasions in bats, or in different hosts14.