The problem for the lab-leak position is that the U.S. has never had access to the Wuhan lab and has thus been unable to reach a definitive answer for more than five years. Now that the CIA has at last come to a conclusion, not all scientists are sold on what it has reported, seeing the results as thinly scientifically sourced.

It was unclear the extent to which the agency has collected new intelligence on COVID-19's origins and whether that new evidence was used to formulate the latest assessment.

The CIA now assesses the virus that causes Covid-19 more likely originated from an accidental lab leak in China, rather than occurring naturally, according to a statement from the agency Saturday, just days after Director John Ratcliffe took the reins.