The lab leak hypothesis postulates that researchers constructed or simply cultured SARS-CoV-2 during research on bat-origin coronaviruses and that an accident allowed the virus to escape the lab and infect humans. However, early isolates of SARS-CoV-2 show the furin cleavage site to be intact, arguing against introduction into humans after laboratory cell culture. Since hypotheses 1 and 2 support the lab leak theory and hypotheses 3 and 4 are consistent with a zoonotic origin, the lab leak- and zoonotic-origin explanations are not equally probable, and the available evidence favors the latter.

In its report, SAGO considered available evidence for the main hypotheses for the origins of COVID-19 and concluded that "the weight of available evidence…suggests zoonotic spillover…either directly from bats or through an intermediate host."[6] WHO requested that China share hundreds of genetic sequences from individuals with COVID-19 early in the pandemic, more detailed information on stored samples and laboratory practices, and access to data from wildlife and animal farming.[6] The report notes that, based on currently available data, both natural spillover and a laboratory-associated incident remain scientifically possible, but evidence is stronger for zoonotic origin and no direct proof of a lab origin has been found.[6]

To evaluate hypothesis #4, of a deliberate manipulation of the virus in a laboratory and subsequent biosafety breach, SAGO analysed the genome structure of the virus and publications and reports addressing the likelihood of manipulation through reverse-genetics but did not find scientific evidence supporting this hypothesis. Without information to fully assess the nature of the work on coronaviruses in Wuhan laboratories, nor information about the conditions under which this work was done, it is not possible for SAGO to assess whether the first human infection(s) may have resulted due to a research related event or breach in laboratory biosafety. To conclude, while a zoonotic origin with spillover from animals to humans is currently considered the best supported hypothesis by the available scientific data, until requests for further information are met or more scientific data becomes available, the origins of SARS-CoV-2 and how it entered the human population will remain inconclusive. It can therefore not be ruled out, nor can it be proven until more information is provided.

On 23 June 2023, the director of national intelligence in the US published findings from intelligence services about the links between covid-19 and a laboratory in the city of Wuhan.[3] But the report found no evidence to prove definitively that a laboratory leak did or did not occur: "Both a natural and laboratory associated origin remain plausible," the report states.[3] Five other US intelligence agencies, however, concluded that natural transmission is more likely.[3] Many virologists, epidemiologists, and other infectious disease experts still say that all available evidence points to SARS-CoV-2 spilling over to humans from an animal host, most likely at a wet market in Wuhan.[3]

The IC assesses that SARS-CoV-2, the virus that causes COVID-19, probably emerged and infected humans through an initial small-scale exposure that occurred no later than November 2019 with the first known cluster of COVID-19 cases arising in Wuhan, China in December.[8] After examining all available intelligence reporting and other information, though, the IC remains divided on the most likely origin of COVID-19.[8] All agencies assess that two hypotheses are plausible: natural exposure to an infected animal and a laboratory-associated incident.[8] One IC element assesses with moderate confidence that the first human infection with SARS-CoV-2 most likely was the result of a laboratory-associated incident, probably involving experimentation, animal handling, or sampling by the Wuhan Institute of Virology; other elements lean toward natural origin or remain agnostic.[8] The IC judges they will be unable to provide a more definitive explanation unless new information shows either the specific animal contact or that a Wuhan lab was handling SARS-CoV-2 or a close progenitor before the outbreak.[8]

A scientific committee convened by the World Health Organization (WHO) has firmly rejected two minority views about how the COVID-19 pandemic began but could not resolve what actually did spark it. The panel's report, released today, found no compelling evidence that scientists created the virus responsible for the pandemic, and it dismissed theories, widely promoted by China, that imported frozen fish introduced it to that country. It concluded, however, there still is not enough hard evidence to say whether the origin was a natural spillover from animals infected with the coronavirus, SARS-CoV-2, or a leak of the pathogen from a laboratory in the city, but "most available and accessible published scientific evidence" supports that SARS-CoV-2 came to humans from bats or an undetermined intermediate species. The report notes that "no evidence has been presented, other than speculation from scientific or intelligence reports, that supports a laboratory-related incident causing the spread of SARS-CoV-2 into the human population."

The SAGO notes that there has not been any new data made available to evaluate the laboratory as a pathway of SARS-CoV-2 into the human population and recommends further investigations into this and all other possible pathways. As things stand, all hypotheses remain on the table, including introduction of SARS-CoV-2 to the human population through a laboratory incident, and zoonotic spillover. SAGO will remain open to any and all scientific evidence that becomes available to allow for comprehensive testing of all hypotheses.

Available evidence indicates that SARS-CoV-2 was originally harbored by bats and transmitted to humans through infected wild animals serving as intermediate hosts at the Huanan Seafood Market in Wuhan, Hubei, China, in December 2019. There is no evidence supporting laboratory involvement, no indication that the virus existed in any lab prior to the pandemic, and no record of suspicious biosecurity incidents. The scientific consensus is that the virus is not the result of genetic engineering; instead, most scientists believe it spread to human populations through natural zoonotic transmission from bats. A declassified June 2023 Office of the Director of National Intelligence report found no evidence of SARS-CoV-2 in labs or biosafety incidents but could not rule out a leak; most U.S. intelligence agencies (with low confidence) favored a zoonotic origin.

On August 27, ODNI released the declassified key takeaways of the assessment on COVID-19 origins.[5] The Intelligence Community overall concluded that the virus was not developed as a biological weapon, and that the IC had not reached a consensus on the origin of the virus, with agencies split between hypotheses of natural exposure and a laboratory incident.[2] In June 2023, ODNI released a new declassified document, which said that the Intelligence Community had still not reached a consensus on the origin of the virus and was unable to rule out the lab leak theory.[2]

On 27 June 2025, the Scientific Advisory Group for the Origins of Novel Pathogens (SAGO) published an independent assessment of the origins of SARS-CoV-2. The report concluded that zoonotic spillover from bats, likely via an intermediate animal, remained the most consistent hypothesis with available scientific evidence, though the exact location, timing, and mechanism remained unknown. Regarding laboratory-related accidents, the report stated this hypothesis could neither be confirmed nor ruled out due to the absence of key biosafety, biosecurity, and staff health records from Wuhan laboratories. Available evidence indicates that SARS-CoV-2 was originally harbored by bats and transmitted to humans through infected wild animals serving as intermediate hosts at the Huanan Seafood Market in Wuhan, Hubei, China, in December 2019. There is no evidence supporting laboratory involvement, no indication that the virus existed in any lab prior to the pandemic, and no record of suspicious biosecurity incidents.

According to current knowledge, a natural origin of SARS-CoV-2 is still much more likely than a laboratory origin. Even after 5 years, there is not a single solid piece of evidence for a laboratory origin. This analysis represents the most compelling evidence to date for a zoonotic origin of SARS-CoV-2. Many other findings from recent years also support the assumption that the virus—similar to the first SARS pandemic in 2003—jumped from bats to humans via an animal intermediate host.

The preponderance of scientific evidence indicates a natural origin for SARS-CoV-2. Yet, the theory that SARS-CoV-2 was engineered in and escaped from a lab dominates media attention, even in the absence of strong evidence. There is currently no verified scientific evidence to support the lab leak hypothesis. Dr. Chan’s New York Times opinion piece misrepresents and underplays the existing scientific data supporting a zoonotic origin of SARS-CoV-2.

This unclassified report attempts to add to the discourse of COVID-19 origins with the understanding that information held by the United States Intelligence Community (IC)…[3] The report concludes that there are indications that SARS-CoV-2 may have been tied to China’s biological weapons research program and spilled over to the human population during a lab-related incident at the Wuhan Institute of Virology (WIV).[3] The Committee states it has not seen any indications that the Chinese military intentionally released SARS-CoV-2, but hypothesizes that General Zhou’s team already possessed SARS-CoV-2 as part of bioweapons research and that a safety incident at the WIV led to its release.[3]

Drawing from peer-reviewed studies, expert briefings, and unpublished data, the report concluded that zoonotic spillover was the most likely cause of the outbreak. However, the report does not eliminate the possibility of a laboratory incident because Chinese officials did not respond to the panel’s requests for information about research activities and biosafety procedures in Wuhan laboratories. According to the committee, a lack of access to crucial raw data and laboratory records means that while a lab-related incident is not supported by current evidence, it cannot be definitively excluded.

After nearly 3.5 years of deliberations, we concluded our independent assessment of the origin of the coronavirus SARS-CoV-2, and provided our report in June 2025 to the WHO director-general. In the 78-page document, we determined that most of the peer-reviewed scientific evidence supports the hypothesis that SARS-CoV-2 has a zoonotic origin, meaning that it came from an animal. But until requests for additional information are met or more data become available, there can be no certainty about when, where and how SARS-CoV-2 entered the human population, and the possibility of a laboratory-associated event therefore remains unproven but not fully resolvable with current data.

The U.S. government does not know exactly where, when, or how the COVID-19 virus—known as SARS-CoV-2—was transmitted initially to humans.[10] We have not determined whether the outbreak began through contact with infected animals or was the result of an accident at a laboratory in Wuhan, China.[10] The virus could have emerged naturally from human contact with infected animals, spreading in a pattern consistent with a natural epidemic; alternatively, a laboratory accident could resemble a natural outbreak if the initial exposure included only a few individuals.[10] The U.S. government has reason to believe that several researchers inside the WIV became sick in autumn 2019, before the first identified case of the outbreak, with symptoms consistent with both COVID-19 and common seasonal illnesses; this raises questions about earlier public claims of "zero infection" among WIV staff.[10]

The most widely supported theory is the natural spillover hypothesis, which posits that the virus was transmitted to humans through a process of accumulated mutations while circulating among animals. This theory is backed by numerous genomic analyses and evolutionary biology studies that support the natural emergence of SARS-CoV-2, with concrete evidence showing adaptation processes through recombination events among various hosts such as bats and pangolins. The second hypothesis is the so-called “lab-leak theory,” suggesting that a new variant may have accidentally escaped from the Wuhan Institute of Virology during serial passage or gain-of-function research on SARS-related viruses. Some circumstantial evidence seems to support this theory, such as reports that some WIV researchers showed COVID-like symptoms early on and records of high-risk coronavirus experiments, but the viruses used in these experiments were not complete, infectious viral particles capable of replication, and pseudo-virus experiments lacked the ability to replicate. Dr. Shi Zhengli consistently emphasized from the outset that the virus was unrelated to their laboratory work.

On Saturday, the Central Intelligence Agency (CIA) announced a change in its earlier assessments, suggesting that the Covid-19 virus likely originated from a laboratory leak in China prior to becoming a worldwide pandemic.[2] However, the agency noted that it holds "low confidence" in this conclusion.[2] A spokesperson stated that the agency assesses with confidence that a research-related origin of the COVID-19 pandemic is more probable than a natural origin, based on the existing body of reports, while emphasizing that both scenarios—research-related and natural origins—remain possible.[2]

Two major hypotheses regarding the origin of SARS-CoV-2 have been debated: a direct zoonotic origin and the introduction of the virus into humans via a laboratory incident.[7] While various papers have suggested that SARS-CoV-2 carries hallmarks of recombinant DNA technologies, this theory has been thoroughly refuted, including by the U.S. intelligence community.[7] The authors note that early isolates of SARS-CoV-2 show the furin cleavage site to be intact, arguing against introduction into humans after extensive laboratory cell culture, and they highlight the lack of direct evidence for either a natural zoonotic reservoir or a specific lab accident so far.[7]

The report outlines four hypotheses but essentially two are based on zoonotic spillover and two are based on a laboratory accident. They stress that they did not have access to raw data when preparing this report, and SAGO and WHO have requested further information from governments, including those that have made assertions about the origins of SARS-CoV-2: China, Germany, and the USA. At the time of writing the report this information had not been provided. The authors describe the evidence as imperfect but argue that the weight of published data points more clearly towards an animal-origin scenario than towards a laboratory origin, noting that intelligence-based claims of a lab origin were not part of their evidence base.

We call on US government scientific agencies, most notably the NIH, to support a full, independent, and transparent investigation of the origins of SARS-CoV-2.[4] In their summary public statement, the US Intelligence Community writes that “all agencies assess that two hypotheses are plausible: natural exposure to an infected animal and a laboratory-associated incident.”[4] The authors state, "We do not assert that laboratory manipulation was involved in the emergence of SARS-CoV-2, although it is apparent that it could have been," and emphasize that there has been no independent and transparent scientific scrutiny to date of the full scope of US-based evidence.[4]

After a 2-year investigation, a House of Representatives committee investigating the COVID-19 pandemic released a wide-ranging final report concluding that SARS-CoV-2 did not originate naturally, as many scientists think, but likely leaked from a lab in Wuhan, China.[4] The committee's 520-page report, released on 2 December, offers no new direct evidence of a lab leak, but summarizes a circumstantial case, including that the Wuhan Institute of Virology used NIAID money to conduct "gain-of-function" studies that modified distantly related coronaviruses.[4] Critics note that the report relies on inference and existing allegations rather than demonstrating that SARS-CoV-2 or a close progenitor was present in the lab before the outbreak.[4]

Germany's foreign intelligence service believed there was an 80–90% chance that coronavirus accidentally leaked from a Chinese lab, German media say. Reports indicate that the country's foreign intelligence agency assessed the lab leak as "likely," despite lacking conclusive evidence. In January, the CIA suggested that the virus "more likely" leaked from a lab rather than originating from animals, though again without definitive proof. Proponents of the natural origin hypothesis, supported in the WHO report, argue that Covid-19 originated in bats and subsequently transferred to humans, likely through an intermediary animal, but scientists have struggled to identify a virus in bats or other animals that aligns perfectly with the genetic structure of Covid-19.

Assessment on COVID-19 Origins is a report of the United States Intelligence Community regarding the origin of the SARS-CoV-2 virus, commissioned on May 26, 2021 by President Joe Biden and submitted on August 24.[2] The report noted that the Intelligence Community did not reach a unanimous conclusion: four agencies and the National Intelligence Council assessed with low confidence that the initial infection was most likely caused by natural exposure to an infected animal or close progenitor virus, while another agency assessed with moderate confidence that the first human infection was most likely the result of a laboratory incident involving experimentation, animal handling or sampling at the Wuhan Institute of Virology.[2] Three other agencies remained unable to agree on either hypothesis without additional evidence, and the Intelligence Community overall concluded that the virus was not developed as a biological weapon.[2]

WHO wants SAGO to also examine the possibility of a laboratory accident being responsible for the emergence of SARS-CoV-2. It will also advise WHO on developing, monitoring, and supporting the next series of studies into the origins of SARS-CoV-2. This role will include rapid advice on WHO’s operational plans to implement the research outlined in the WHO-convened Global Study of Origins of SARS-CoV-2: China Part report published on March 30, 2021, including tracing related coronaviruses in wildlife and further assessment of any potential laboratory-associated pathways.

Data from environmental samples at the Huanan Seafood Market showed genetic evidence of SARS-CoV-2 virus on machines that were used to kill animals and on brushes used to clean them, and they found mammalian DNA representing raccoon dogs, palm civets, and bamboo rats—all of which are animals that could transmit the virus from bats to humans. This was described as "clear evidence" that the market was where the virus started and how it started, consistent with an animal-to-human spillover event. The video also notes that viruses the Wuhan Institute of Virology was working with (such as RaTG13/WIV1) were "not even close" to being precursors of SARS-CoV-2, and there is no evidence that lab workers got sick from novel engineered viruses.

Newly released intelligence records show that as recently as January 2025, the U.S. intelligence community planned to create an independent panel of outside experts to study how the COVID-19 pandemic began, suggesting officials considered the question sufficiently unresolved to warrant additional review even after years of investigation and the public release of a 2023 intelligence assessment.[1] The January 2025 National Intelligence Council memo, titled “Updated IC Assessments of COVID-19 Origins,” incorporates the CIA’s shift toward assessing that a “research-related incident” origin of the pandemic is more likely than a natural spillover event, although this assessment is held with low confidence.[1] The memo notes that the CIA joined the FBI and Department of Energy in favoring a laboratory-event origin while emphasizing that both hypotheses remain plausible and that four other intelligence agencies and the National Intelligence Council continued to favor a natural-origin explanation.[1]

The WHO Scientific Advisory Group for the origins of Novel pathogens (SAGO) says that, until further data becomes available, the origins of SARS-CoV-2, the virus responsible for the COVID-19 pandemic, remain unsolved. According to its recent report, SAGO states that, as it stands, all hypotheses remain on the table, including zoonotic spillover and a lab leak. That earlier team's report had favored a natural origin of SARS-CoV-2, calling a possible leak from a lab in Wuhan, China, "extremely unlikely."

The CIA has "low confidence" in its assessment that the COVID-19 virus more likely came from a lab rather than natural transmission.[8] Officials explain that "low confidence" reflects that the information used is "scant, questionable, or fragmented," and that the agency’s judgment on a lab-related origin for COVID-19 is tentative and could change with new evidence.[8] The video segment notes that other U.S. agencies, including the FBI and Department of Energy, have also leaned toward a lab-related incident, while several intelligence agencies still favor a natural spillover origin, underscoring the lack of consensus.[8]

A lab-related incident involving gain-of-function research is the most likely origin of COVID-19, according to this document. It claims that data show all COVID-19 cases stem from a single introduction into humans, which it argues runs contrary to previous pandemics where there were multiple spillover events. The document asserts: "By nearly all measures of science, if there was evidence of a natural origin it would have already surfaced. But it hasn’t." It further contends that the virus possesses a biological characteristic that is not found in nature, using these points to argue that a lab leak is the most plausible explanation.

The preponderance of scientific evidence indicates a natural origin for SARS-CoV-2. Yet, the theory that SARS-CoV-2 was engineered in and escaped from a lab dominates media attention, even in the absence of strong evidence. The article argues that promoting the lab leak hypothesis without robust supporting data has caused harms including the erosion of trust in science and public health, and diversion of attention from preventing future zoonotic spillovers.

World Health Organization Scientific advisory group issues report on origins of COVID-19. The WHO Scientific Advisory Group for the Origins of Novel Pathogens (SAGO), a panel of 27 independent, international, multidisciplinary experts, today published its report on the origins of SARS-CoV-2, the virus responsible for the COVID-19 pandemic. SAGO has advanced the understanding of the origins of COVID-19, but as they say in their report, much of the information needed to evaluate fully all hypotheses has not been provided… "As things stand, all hypotheses must remain on the table, including zoonotic spillover and lab leak. We continue to appeal to China and any other country that has information about the origins of COVID-19 to share that information openly…" In its report, SAGO considered available evidence for the main hypotheses and concluded that "the weight of available evidence…suggests zoonotic spillover…either directly from bats or through an intermediate host."

Multiple independent genomic analyses have found that SARS-CoV-2’s genome is consistent with known patterns of coronavirus evolution and does not bear signatures of laboratory engineering. Comparisons with related bat coronaviruses show that SARS-CoV-2 likely emerged through recombination and natural selection in animal hosts, similar to previous zoonotic coronaviruses such as SARS-CoV-1 and MERS-CoV. Global virology and evolutionary biology communities broadly consider a natural zoonotic origin more plausible than a laboratory origin, while acknowledging that definitive identification of the intermediate host remains outstanding.