Beijing has never fully co-operated with international investigators, impeding the search for a definitive answer. But scientists continue their quest to establish the causes of a global health crisis that killed millions of people, caused trillions of dollars of economic damage and increased fears over the risks of virus research.

China said on Monday it was "extremely unlikely" that the coronavirus came from a laboratory, after the United States' Central Intelligence Agency (CIA) said it believed the virus had more likely come from such a facility rather than natural transmission.

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.

The Central Intelligence Agency with a "low confidence" has changed its stance and concluded that it's likely the COVI-19 virus was leaked from a Chinese lab before it became a global pandemic five years ago.

T he Central Intelligence Agency (CIA) recently assessed that the COVID-19 pandemic is more likely to have originated from a laboratory leak in Wuhan, China, though it maintains l