After more than five years of investigation, the World Health Organization’s Scientific Advisory Group for the Origins of Novel Pathogens has concluded that whilst evidence supports a natural zoonotic spillover as the most likely origin of SARS-CoV-2, critical data gaps prevent definitive conclusions and a laboratory-related incident cannot be ruled out.
The World Health Organization’s Scientific Advisory Group for the Origins of Novel Pathogens (SAGO) has published its most comprehensive assessment to date on the origins of SARS-CoV-2, concluding that whilst available evidence supports natural zoonotic transmission, significant data gaps prevent a definitive determination of how the pandemic began.
The 78-page report, published on 27 June 2025, represents the culmination of extensive analysis by 27 independent international scientific experts who reviewed peer-reviewed literature, government reports, and intelligence assessments spanning from the virus’s emergence through to 2025.
Evidence supports zoonotic transmission
“The weight of available evidence reviewed by SAGO suggests zoonotic spillover of SARS-CoV-2 into the human population, either directly from bats or through an intermediate host,” the authors state. However, they emphasise: “SAGO cannot conclude with certainty where and when this occurred, nor if the HSM [Huanan Seafood Market] was indeed the first instance of spillover into the human population, or the site of further spillover and amplification.”
The assessment highlights compelling metagenomic evidence from the Huanan Seafood Market, where researchers identified mitochondrial DNA from animals known to be susceptible to SARS-CoV-2 infection, including raccoon dogs, in the same stalls where environmental swabs tested positive for the virus. “The data confirms that these animals were present before the market was closed on 1 January 2020 and may have been a source for human infection,” the report notes.
Genomic analyses revealed evidence of two separate introductions of SARSCoV-2 lineages into the human population, with evolutionary analyses suggesting these occurred after November 2019. The closest known precursor viruses remain RaTG13 from bats in China (96.1% genomic similarity) and BANAL-52 from Laos (96.8% similarity), though these are still too genetically distant to be direct sources of the pandemic virus.
Laboratory origin hypothesis remains unresolved
Critically, SAGO could not adequately assess the possibility of a laboratory-related incident due to lack of access to essential information. “Information and evidence is also lacking to assess the possibility of a laboratory origin – either the evidence is not available or has not been provided to the scientific community,” the authors explain.
The group repeatedly requested access to health records of laboratory staff, documentation on biosafety procedures, and details of coronavirus research conducted at facilities including the Wuhan Institute of Virology and Wuhan Centers for Disease Control. “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,” the report states.
Persistent data gaps hamper investigation
The assessment identifies numerous outstanding investigations that could clarify the pandemic’s origins. These include access to more than 500 genetic sequences from early COVID-19 patients that remain unpublished, detailed information about animal sources at wet markets in Wuhan, and comprehensive upstream investigations of wildlife farms supplying the Huanan market.
SAGO found no credible evidence supporting the cold chain hypothesis
– that frozen imported products introduced the virus to China – nor theories of deliberate viral manipulation. “Hypotheses submitted to the SAGO or available in the public domain on intentional manipulation of the virus however, are not supported by accurate science,” the authors conclude.
Call for continued investigation
The report emphasises the moral imperative of understanding COVID19’s origins: “This is not solely a scientific endeavour it is a moral and ethical imperative. Understanding the origins of SARS-CoV-2 and how it sparked a pandemic is needed to help prevent future pandemics, save lives and livelihoods, and reduce global suffering.”
SAGO urges all governments, particularly China, to share additional data and allow independent investigations. “The COVID-19 pandemic has caused so much suffering and devastation globally for the world not to know exactly how this pandemic started,” the authors state.
The assessment concludes that until critical information gaps are addressed, “the origins of SARS-CoV-2 and how it entered the human population will remain inconclusive.”
Reference:
World Health Organization. (2025). Independent assessment of the origins of SARS-CoV-2 from the Scientific Advisory Group for the Origins of Novel Pathogens (SAGO). World Health Organization, 27 June 2025.
