In a Sherlock Holmes story, a racehorse disappears on the night before a big race. Holmes is called in to investigate. He focuses not on the evidence that was collected but, instead, on a bit of key evidence that is missing. A dog that should have barked at the horse's kidnapper did not.
Since the earliest days of the SARS-CoV-2 pandemic, there have been suspicions that the virus was created by humans rather than arising in the wild. Evaluating different theories about the origins of SARS-CoV-2 might require an approach similar to that taken by Holmes. A particular bit of missing evidence might be key to deciding whether the SARS-CoV-2 virus originated in a Chinese research lab or in the wild.
The US Senate just issued a report that carefully lays out the evidence for the lab-leak theory. The response has been, unsurprisingly, polarized.
Science magazine calls the evidence circumstantial but admits there is reason for suspicion. The Washington Post devotes more column inches to critics of the report than to the report’s findings and suggests that the report is a political document designed largely as a template for a future Senate investigation. John Campbell, a British nurse and researcher who has a popular YouTube series about issues related to COVID, analyzes the report here. The most comprehensive bibliography and analysis is on a website maintained by independent researcher Jamie Metzl.
All agree that we will likely never know the true story because crucial early evidence from China has been either covered up or destroyed. Metzl says that, to get an answer, we need “a full and unrestricted international forensic investigation into the origins of COVID-19 with full access to all relevant data, lab records, biological samples, and people in China and, as appropriate, beyond.” The Senate report critically notes that China prohibits sharing or publishing any information without government review and approval. As a result, we don’t know when the first cases were diagnosed, when the viral genome was first sequenced, or how vaccines were developed in China in less than half the time as in the US and Europe.
One epidemiological factor is crucial. If this was not a lab leak, then it was a virus that somehow jumped from animals to humans. When that happens, there must be an animal reservoir of the virus. But there is no such reservoir for SARS-CoV-2. That is, there is no published genetic evidence that SARS-CoV-2 was circulating in animals prior to the start of the COVID-19 pandemic or afterwards. A recent comprehensive review noted, “Understanding where the SARS-CoV-2 adapted to humans is critical for our understanding and prevention of future outbreaks of not only COVID-19 but, also, other potential diseases. The best suggestion is that the virus evolved from a bat coronavirus; however, no intermediate host has yet been identified.”
To be sure, this negative evidence. That is, it doesn’t prove there was a lab leak. But it makes the alternative hypothesis less likely. It is similar to Holmes solving a crime by recognizing the importance of the fact that the dog did not bark. Holmes notes, “I had grasped the significance of the silence of the dog, for one true inference invariably suggests others.”
This will not be the last pandemic. It is crucial to understand what was done right and what was done wrong in the early days of the pandemic so that we can better prepare for the next one. As John Campbell puts it, “The human race made a complete pig’s ear of the initial management of this virus. We need to get it right next time.”
It also matters as we examine our own willingness and ability to disentangle science and politics. Sometimes, science leads us to conclusions that we find politically troublesome. That doesn’t mean they are wrong.