Lab leak theory: Behind the science and the scientists

Trump fueled accusations that the Wuhan Institute of Virology, a research lab in the same city where the first Covid-19 cases were reported, was connected to the outbreak, and on numerous occasions called the pathogen the "Wuhan virus" or "kung flu." "At the time, it was scarier to be associated with Trump and to become a tool for racists, so people didn't want to publicly call for an investigation into lab origins," she said.Now, more scientists are comfortable confronting the gamut of plausible theories — particularly given China's opacity on the topic — though many still caution that entertaining the idea of a lab leak requires clear scientific proof, which has not yet materialized."There has been no new evidence over the past 16 months that the virus had a lab origin," said Maciej Boni, an associate professor of biology at Penn State University, who specializes in tropical disease epidemiology and viral evolution.A number of theories about how the virus may have emerged have been thrown out, but most that remain fall under three possible scenarios:The virus evolved naturally before spilling over into humans from an infected animal.The virus evolved naturally but an employee at the lab became infected from a sample and accidentally "leaked" it into the community.Scientists at the lab were manipulating virus samples and accidentally or intentionally released the pathogen.What makes the virus's origin a complicated matter is that the various threads can be difficult to reconcile. In research published in November 2020 by scientists at the Wuhan institute, serum samples from four of the mine workers were tested and showed no trace of SARS-CoV-2, the virus that causes Covid-19.Separately, a U.S. intelligence report disclosed that three researchers at the Wuhan institute sought treatment at a hospital after falling ill in November 2019, as was first reported by The Wall Street Journal in May.During the WHO-led probe earlier this year, officials at the Wuhan institute said all staff members at the lab tested negative for Covid-19 antibodies. Its leaders have been adamant that the virus did not escape from their facility, but the Chinese government's reticence to share records and test results have cast suspicion over what the lab's scientists knew — and when.Though far from conclusive, both the intelligence report and the mine workers' mysterious illnesses have been presented as circumstantial evidence that scientists at the Wuhan institute were studying risky coronaviruses similar to SARS-CoV-2, and that the virus may have escaped from the lab, perhaps after an employee became infected.The mine incident also drew attention to a separate SARS-like virus that was collected by Chinese researchers in 2013 from a bat in Yunnan province. We just don't have the ability to make those kinds of changes."In other words, the experts say, it's unlikely that scientists could snip and splice bits of a virus or tweak a pathogen's genome in such a way that would create SARS-CoV-2, even if researchers were using closely related coronaviruses."We're very good at imitating nature — we have, for instance, been able to synthesize polio virus — but our ability to manipulate or change the sequence of viruses is still limited," Chiu said.Chan, of the Broad Institute, wasn't ready to rule out the possibility of genetic engineering, saying that if minor tweaks were being made to virus samples, it could be difficult to detect the fingerprints of such work."You can do recombination without leaving a trace," she said.