Nature Researchers summarize key insights from the world’s first comprehensive investigation into how a pandemic started. We are 23 of the 27 original members of the Scientific Advisory Group for the Origins of Novel Pathogens (SAGO) for the World Health Organization (WHO). After nearly 3.5 years of deliberations, we concluded our independent assessment of the origin of the coronavirus SARS-CoV-2, and provided our report1 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.
Although the term of the first SAGO group ended in October last year, meaning we are no longer members, the WHO has proposed a second term for SAGO and issued a call for new participants. Our 2025 report1 provides recommendations for subsequent investigations seeking to establish the origin of the COVID-19 pandemic. In the meantime, with the politicization and speculation around the origin of the pandemic showing no signs of abating, 23 of us mark the close of SAGO’s first chapter by clarifying our position on the origin of SARS-CoV-2 and the science behind it in a more accessible way.