What we know about the lab leak theory and the origins of Covid

Scientists and spy agencies have tried to determine the origin of the coronavirus, but it is difficult to obtain conclusive evidence and the agencies of country's intelligence are divided.

WASHINGTON - The Department of Energy's "low confidence" conclusion that an accidental lab leak in China has very likely caused the coronavirus pandemic has renewed questions about what sparked the worst public health crisis in a century - and whether the virus at the heart of it was somehow linked to scientific research .

Scientists and spy agencies have tried diligently to answer this question, but conclusive evidence is hard to come by. The nation's intelligence agencies are divided and none of them changed their conclusions after seeing the Energy Department's findings, officials said.

Scientists who have studied the genetics of the virus, and the patterns by which it has spread, say the most likely cause is that the virus jumped from living mammals to humans - a scientific phenomenon known as “zoonotic spillover” – at the Huanan Seafood Wholesale Market in Wuhan, China, the city in which the first of the Covid-19 cases emerged in late 2019.

But other scientists say there is evidence, albeit circumstantial, that the virus originated from a lab, possibly the Wuhan Institute of Virology, which had deep expertise in researching coronavirus. Laboratory accidents happen; in 2014, after accidents involving avian flu and anthrax, the Centers for Disease Control and Prevention strengthened their biosecurity practices.

The debate is politically tense. The lab leak theory gained traction among Republicans in the spring of 2020 after President Donald J. Trump, who used inflammatory terms to blame China for the pandemic, clung to the idea. Many Democrats were unconvinced by the lab leak hypothesis; some say they believe in the explanation of natural causes, and others say there may never be enough intelligence to draw a conclusion. , who are investigating the origins of the pandemic. But politics aside, experts say understanding what caused a public health crisis that killed nearly seven million people could help researchers figure out how to prevent the next one.

Here's what we know and don't know about the origins of the coronavirus.

It is often difficult to find the origins of viruses, but China has compounded this problem by making it very difficult to collect evidence.

As Chinese researchers are arrived to take samples at the Huanan market, the police had closed and disinfected the market because a number of people linked to it had fallen ill with what would later be recognized as Covid. No live market animals were left.

Some scientists also believe China provided an incomplete picture of early Covid cases. And they worry that a directive to hospitals early in the outbreak to report illnesses specifically linked to the market may have led doctors to ignore other cases without those links, creating a biased snapshot of the spread. p>What did scientists do to investigate?

Experts tried to get around the holes in the data.

The scientists looked at inpatient cases before the call went to doctors to look for links to the market. They also mapped the locations of the first Covid cases in Wuhan – including the two people who were originally linked...