NBC News The science around the lab leak theory hasn't changed ...

The researchers offered near-uniform summations that few conclusions can be drawn based on the available scientific evidence, but they noted that the context and circumstances  of the origin debate have changed, particularly as critics point out that China hasn't been fully transparent about the earliest days of the pandemic.The shift reflects how some scientists who previously avoided the topic or were quick to dismiss it are grappling with enduring uncertainties about the virus's origin, free from the politicization that clouded such discussions during the Trump administration.Chan said there had been trepidation among some scientists about publicly discussing the lab leak hypothesis for fear that their words could be misconstrued or used to support racist rhetoric about how the coronavirus emerged. Trump fueled accusations that the Wuhan Institute of Virology, a research lab in the city where the first Covid-19 cases were reported, was connected to the outbreak, and on numerous occasions he 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 about the topic — although many still caution that entertaining the idea of a lab leak requires clear scientific proof, which hasn't 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. Its leaders have been adamant that the virus didn't escape from the facility, but the Chinese government's reluctance to share records and test results has cast suspicion over what the lab's scientists knew — and when.Although they are far from conclusive, 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 Chinese researchers collected from a bat in Yunnan province in 2013. 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.