LONDON: A top virologist on the UN health body's panel, Professor Marion Koopmans, has said that the World Health Organization (WHO) should never have dismissed the lab leak theory about the origin of the Covid pandemic.

The WHO in its initial assessment in 2021 had stated that it was "extremely unlikely" that Covid might have spilled into humans from a lab.

Koopmans, who heads the Department of Viroscience at Erasmus Medical Center in Rotterdam in the Netherlands, is one of 12 people investigating the emergence of the pandemic on behalf of WHO.

Speaking to the BBC podcast "Fever: The Hunt for Covid's Origin", Koopmans said the theory that the virus escaped from a secretive lab in Wuhan could never be ruled out, the Daily Mail reported.

"We shouldn't have done that," she added.

A team of experts from the WHO spent four weeks in China in January 2021 to investigate whether Covid-19 is the result of a lab-leak.

The agency announced that "all hypotheses remain on the table," and that "we have not yet found the source of the virus, and we must continue to follow the science and leave no stone unturned as we do."

But the global health body ruled that the natural-origins theory was the most likely -- and placed a leak from the Wuhan Institute of Virology as "extremely unlikely" and behind the frozen-food origin theory.

China, on the other hand, stated that the virus began in a US research facility in Maryland or in imported frozen food packaging.

Meanwhile, Koopmans said that she hasn't ruled out both theories of the frozen-food and lab-leak.

"Neither of them are ruled out in my mind," she was quoted as saying.

Asked whether including the frozen-food theory in the final report undermined WHO's mission, Koopmans said: "I don't think so."

"Again, as a scientist, looking at the literature and looking at what is possible, I felt we should also not throw it out because it was pushed politically."

In May, former Chinese CDC head Dr George Fu Gao, also said that the theory that Covid-19 is the result of a lab-leak should not be discounted. Gao directed China's CDC when Covid first emerged in Wuhan.

"You can always suspect anything. That's science. Don't rule out anything," Gao was quoted as saying to the same BBC podcast.

China has since the beginning dismissed any suggestion the disease may have originated in a Wuhan laboratory.

More than two years after the pandemic that has infected over 763 million and claimed more than 6.9 million lives globally, the origins of Covid-19 remain unclear.