The coronavirus is likely to have emerged in bats and spread to another animal before reaching the human population, according to a study by the World Health Organization and Chinese scientists which is expected to be released on Tuesday.
The 123-page report, which NBC News obtained before publication, also found that it is “extremely unlikely” that the virus has leaked from a laboratory, a theory that has flourished among Chinese skeptics even though it is based on much on circumstantial evidence.
The results are the result of a joint study by Chinese scientists and a WHO-led team that was in China last month to investigate the origin of the virus. The investigation has been at the center of political tensions since its inception; Officials in the Biden administration have blamed China for what they say is a lack of transparency about how the virus came about. Other critics said the investigation was insufficient because many Chinese scientists involved in the investigation are affiliated with government-run institutions and because investigators did not have full access to laboratory records and data. raw.
In the report, the research team detailed the most likely scenarios that caused the virus to spread to humans, but many questions remain unanswered. Identifying the source of a virus, which can take years or even decades, is an important way for scientists to understand the emergence of infectious diseases and prevent similar outbreaks.
According to the researchers, the most likely route of transmission was from bats to humans via an intermediate animal host. Direct transmission from bats to humans was also considered a “possible to probable route”.
The report recommended further research for these and other scenarios, including retrospective studies of the first known cases linked to a seafood market in Wuhan, China.
Wuhan market was the site of the first cluster of reported human cases, but the WHO report said it was not clear if this was the original source of the outbreak.
Marion Koopmans, a Dutch virologist who was part of the WHO delegation, said in an interview this month that while the first large clusters were reported in Wuhan, it is not clear whether the virus originated there. .
Koopmans said the investigation found no credible evidence that the coronavirus had leaked from a lab. The laboratory leak hypothesis was touted by President Donald Trump and most recently promoted by Dr. Robert Redfield, the former director of the Centers for Disease Control and Prevention.
“I am of the opinion that I still believe that the most likely etiology of this pathogen in Wuhan was from a laboratory. Escaped, ”Redfield said in an interview with CNN on Friday. “Other people don’t believe it. It’s good. Science will eventually find out. “
At a White House Covid-19 response team briefing later Friday, the government’s senior infectious disease specialist, Dr.Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said Redfield “was only expressing an opinion”.
Determining the origin of a virus can be a long process, and although the WHO study says a lab leak is “extremely unlikely”, it said it was impossible to rule it out completely. .
Robert Garry, a virologist at Tulane University School of Medicine who was not involved in the WHO investigation, said the research team was correct in largely rejecting the idea. that the virus had leaked from a laboratory.
About a year ago, Garry and his colleagues analyzed the genome sequence of the coronavirus that emerged in Wuhan and determined that the virus was likely to have evolved from nature. In other words, scientists have found no evidence that the virus was designed or modified at a research facility.
Garry said more research would be needed to understand the origin of the virus, but added that careful work is crucial to protect against similar or worse outbreaks.
Understanding how the coronavirus appeared in bats or other species “will provide critical data on the evolution and ecology of potential pathogens, guidance for detecting their emergence, and suggest solutions for the design of counter- appropriate action, ”Garry said.