In a letter to the journal Science several prominent scientists express that the origin of the novel coronavirus is still unknown and the theory that it was caused by a lab leak needs to be taken seriously until proven wrong.

COVID-19, which emerged in China in late 2019, has killed 3.34 million people, cost the world trillions of dollars in lost income and upended normal life for billions of people.

“More investigation is still needed to determine the origin of the pandemic,” said the 18 scientists, including Ravindra Gupta, a clinical microbiologist at the University of Cambridge, and Jesse Bloom, who studies the evolution of viruses at the Fred Hutchinson Cancer Research Center.

“Theories of accidental release from a lab and zoonotic spillover both remain viable,” the scientists including David Relman, professor of microbiology at Stanford, said in a letter to the journal Science.

The authors of the letter said the World Health Organization’s investigation into the origins of the virus had not made a “balanced consideration” of the theory that it may have come from a laboratory incident.

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