"Lab leak" theory of COVID's origin rises in prominence

President Biden ordered the U.S. intelligence community on Wednesday to "redouble their efforts" to determine whether COVID-19 first emerged from a laboratory in Wuhan or through animal-to-human transmission.

Flashback: The "lab leak" theory was initially dismissed by most scientists and public health officials and spread mainly by some of China's loudest critics, including President Trump. Many media outlets steered clear, and it faded into the background of the COVID-19 debate.

Now, everyone from Biden to 18 leading biologists (writing in Science) to Anthony Fauci to WHO chief Tedros Adhanom Ghebreyesus has called for further investigation.

• One reason is that no conclusive evidence has emerged for the animal spillover hypothesis, which had long been regarded by many scientists as the most likely explanation. It can take years to trace a virus back to an animal source.
• Another related reason is China's stonewalling of any thorough investigation — a characteristic response from Beijing that has nonetheless fueled suspicions that the government has something to hide.
• The outright dismissal of the lab theory in the report following a WHO investigation that was tightly controlled by China only fueled those suspicions further (particularly as the report took seriously the bizarre theory that the virus was imported in frozen food).
• Then there's the drumbeat of circumstantial news reports like the one from WSJ about workers at the Wuhan Institute of Virology falling ill in November 2019.

• There's also the history: "[S]cientists now believe that the H1N1 seasonal flu that killed thousands every year from 1977 to 2009 was influenza research gone feral," writes Donald McNeil, formerly the NYT's lead reporter on the pandemic and a recent convert to the lab leak theory.

The bottom line: We may never know how a pandemic that has killed at least 3.5 million people and thrown perhaps 115 million more into poverty began. Many scientists continue to point to animal spillover. But the lab leak theory has officially gone mainstream.

Go deeper: What the lab leak theory means for scientific research