What we know about the origin of COVID-19, and what remains a mystery
The precise origin of SARS-CoV-2, the coronavirus that causes COVID-19, remains unknown and continues to be a source of contentious debate. Two theories dominate the conversation: a natural spillover from infected animals, and a "lab leak" associated with coronavirus research in Wuhan, China, the city where the first cases of an unusual pneumonia-like illness were reported.
President Biden in May 2021 asked intelligence agencies to probe the origins of the virus, but they were unable to reach a consensus. Most favored, with "low confidence," the natural spillover theory. Peer-reviewed scientific papers published last year bolstered the case that the virus came from animals sold at the Huanan Seafood Wholesale Market in Wuhan.
But critics of the natural spillover theory point out that investigators did not find any virus-infected animals that could have been the source of the outbreak. That fact was highlighted in a report issued last year by Republican staff on a Senate committee looking into the origin of the virus. The report also raised questions about safety protocols at a Wuhan laboratory. While not ruling out a natural spillover, the Republican staffers concluded that a "research-related incident" was the "most likely" origin.
Now House Republicans, newly in charge of their chamber, have opened a fresh probe of COVID's origin.
What new evidence has emerged about the origin of COVID-19?
There's not much that is new and compelling on the scientific front. But this is such an explosive issue that incremental developments can generate big headlines.
The newest political development is that the intelligence community produced an updated version of its 2021 report to President Biden. By and large that assessment has not changed. But The Wall Street Journal reported on Feb. 26 that the updated assessment reveals the Energy Department has shifted from a neutral stance on the virus' origin to one favoring, with "low confidence," a lab leak.
The updated intelligence report remains classified, so it is unclear why the Energy Department changed its view.
Four other agencies and the National Intelligence Council continue to favor the natural origin with "low confidence." The FBI, however, continues to state with "moderate confidence" that it favors a laboratory origin.
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Why is the Energy Department involved in COVID investigations?
The Energy Department runs major national laboratories and spends billions every year on scientific research, including work on quantum physics and fusion energy. The COVID origins analysis was performed by a little-known scientific team that specializes in emerging security threats, The Washington Post has reported.
National security adviser Jake Sullivan told CNN on Sunday that Biden asked for the national labs to be involved in the COVID origin investigation "because he wants to put every tool at use to be able to figure out what happened here."
When asked about its new stance on a lab leak, a department spokesperson referred questions to the intelligence agencies, saying, "the Department of Energy continues to support the thorough, careful, and objective work of our intelligence professionals in investigating the origins of COVID-19, as the President directed."
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What evidence exists for a lab leak?
The Wuhan Institute of Virology is the primary focus of the lab leak conjectures, because it is a major research center that did extensive work on coronaviruses.
Many versions of the lab leak theory require some level of secrecy by researchers in China. But there are also scenarios that involve an accidental release of the virus without anyone realizing it. For example, researchers at the institute collect wild bats, which are ancestral sources of coronaviruses. Someone involved in this process could have inadvertently introduced the virus into the Wuhan population.
Proponents of a lab leak also point to experiments at the lab that manipulate viruses in ways that could make them more transmissible - "gain of function" experimentation. The goal of such research is to understand how a pathogen might evolve to become more of a threat, but critics have decried this as inviting disaster.
Supporters of the lab leak theory have pointed to an unfunded proposal for an experiment that, they argue, could be a recipe for making a virus like SARS-CoV-2. And one recent experiment at the Wuhan Institute of Virology, funded in part by the National Institutes of Health through a grant to the organization EcoHealth Alliance, has come under special scrutiny, creating a political headache for NIH officials.
That experiment could not have produced SARS-CoV-2, according to scientists who analyzed it. But critics believe this kind of viral manipulation - or some other type of experimentation that creates novel viruses or enhances their transmissibility - could have led to the creation of SARS-CoV-2.
That idea remains speculative. There is no evidence that the virus or its progenitor was in any laboratory before the outbreak in late 2019. Chinese scientists have said they were not working with the virus. Chinese officials, however, have not been cooperative with international investigators, and have instead floated improbable theories, such as that the virus entered China in a shipment of frozen fish, or as the result of American biological research efforts.
The World Health Organization recently abandoned an effort to probe the origin of the virus, citing the political obstacles to the inquiry.
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What is the evidence for a natural origin?
Many experts note that a natural origin would line up with the history of pandemics, which typically start with spillovers from animals - no laboratory help required. SARS, the previous coronavirus outbreak in China that began in 2002, emerged in a market spillover. It has been genetically traced back to horseshoe bats, and it infected humans via an intermediate species: civet cats sold in markets.
A large percentage of early SARS-CoV-2 infections documented in Wuhan were clustered around the Huanan Seafood Market, where animals were sold and butchered in conditions that scientists say were ripe for a spillover. Many species of animals sold there are now known to be capable of infection with SARS-CoV-2.
Two papers published last summer in the journal Science argued in favor of the market as the epicenter of the outbreak.
Based on genomic analysis of early infections, one paper argues there were at least two separate spillover events in the market, producing two distinct lineages of the virus. The other paper says the geographical clustering of early infections, combined with environmental samples showing traces of the virus in areas where animals were sold, point clearly to the market as the epicenter of the outbreak.
But the scientists favoring the market origin acknowledge that there are missing pieces in the narrative. They have not identified which animals were infected or where they came from. The market was closed and cleaned and the animals culled within a few days of the outbreak.
"Everything upstream of this - which animals, where did they come from, how it's all connected - is completely unknown at this stage," Kristian Andersen, an infectious-disease researcher at Scripps Research and co-author of both papers, said in a media briefing at the time.
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So will we ever know the origin of COVID?
The origin of COVID has become so polarizing that it may never be resolved to widespread satisfaction. Because the issue is politicized, it is vulnerable to motivated reasoning - interpreting facts to fit a preferred narrative.
The narrative could change dramatically with a new scientific or investigatory revelation that produces unassailable and unambiguous evidence. For example, a whistleblower in a laboratory could reveal credible evidence of the presence of SARS-CoV-2 in a research facility before the outbreak. Or, researchers could find the progenitor of SARS-CoV-2 in archived tissue samples taken from commercially trafficked animals.
In the meantime, the contentious situation has put increased attention on whether laboratory research on viruses is worth the risk of an accident.
There is a significant, ongoing divide among scientists about the safety of laboratory research that involves the manipulation of pathogens. Lab leaks can happen. Research on viruses may involve manipulating them in ways that could, in theory, lead to an accident - and a pandemic.
Due to ongoing concerns about research safety, the National Science Advisory Board for Biosecurity has issued a preliminary report calling for tightening of oversight of research on potential pathogens. Those changes have been in process for many years and are not a response to the lab leak theory. But questions about COVID's origin inevitably shadow any discussion about how to balance the risks and benefits of pathogen research.
On Feb. 26, Gerald Parker, a Texas A&M University professor and chair of the biosafety board, wrote on Twitter, "We have a moral obligation to determine to the best of our ability how SARS2 emerged to cause the worst pandemic in over 100 years."