The United States' politicizing of efforts to trace the origins of COVID-19 will lead to more confusion and a protracted blame game, which will ultimately undermine the scientific process of discovering the cause of the worst pandemic in a century, experts said.

Saturday marked the third anniversary of the World Health Organization declaring COVID-19 a global pandemic. WHO Director-General Tedros Adhanom Ghebreyesus said on Twitter that understanding the origins of COVID-19 remains a scientific and moral imperative to help the world prevent future outbreaks.

Last week, the journal Science published an article lamenting that science had taken a back seat at the first US congressional hearing on the origins of the novel coronavirus as US Democrats and Republicans engaged in a sparring match that shed no new light on the issue.

"It was very disappointing, and almost unbelievably divorced from the science," Michael Worobey, an evolutionary biologist from the University of Arizona, told Science. His published research in the journal, supporting natural "zoonotic" origins of the virus, has been attacked by proponents of the "lab-leak theory".

Last month, the US Department of Energy changed its view about the likely cause of COVID-19 from "undecided" about its origins to suspecting a "lab leak" behind the pandemic. The view was based on a new classified intelligence report provided to the White House and key members of the US Congress.

Maria Van Kerkhove, WHO's technical lead on COVID-19, said on Twitter that she was frustrated that the US did not share additional information with WHO on its latest assessment of the virus' origins.

"We don't completely have the answers to how this pandemic began, and it remains absolutely critical that we continue to focus on this," she said.

Despite the Department of Energy claiming it had reached the new conclusion in "low confidence", the shift has reignited speculation and conspiracy theories regarding the origins of COVID-19.

Since the start of the pandemic, some US politicians have frequently alleged that the virus was manufactured and escaped from a lab in Wuhan, Hubei province. China firmly opposed such speculations.

Last week, the US Senate passed a bill requiring the declassification of information related to COVID-19 origins. However, the bill stated the reason for the disclosure as US politicians' belief that the virus had leaked from a Chinese lab.

Despite investigations by WHO, global scientific communities haven't reached a definite conclusion on the virus' origins. But they generally lean toward favoring the spillover hypothesis, which says that the virus jumped from bats to humans.

US Director of National Intelligence Avril Haines said last week that the intelligence community has reached a broad consensus that the pandemic was not the result of a bioweapon or genetic engineering, though it is still undecided on the virus' origins.

Last week, Chinese Foreign Ministry spokeswoman Mao Ning said the US has been "politicizing, weaponizing and manipulating" the efforts to trace the virus' origins to smear and attack China without providing evidence.

China has always supported and participated in global science-based origins tracing of the virus, while firmly opposing political manipulation of the issue in any form, she said.

Chinese scientists have shared vital data and made insightful discoveries with international peers on the origins of COVID-19.

One example is a recent study by Mang Shi from Sun Yat-sen University in Guangdong province and Edward Holmes from the University of Sydney, Australia. They identified a bat virus, BtSY2, that is closely related to SARS-CoV, which caused a global outbreak in 2003, and SARS-CoV-2, the original COVID-19 strain, suggesting a history of recombination events that had taken place.

The study, published on the preprint repository bioRxiv in November, revealed an unexpectedly high frequency of co-infection of viruses in bats.

Recombination is a mechanism of coronaviruses that allows them to exchange genetic materials, leading to new genetic variants and traits. This study adds to the mounting evidence that the virus had originated from nature.

On March 1, Foreign Ministry spokeswoman Mao said the US putting its intelligence community in charge of a matter of science is a clear sign that the issue has been politicized. She said the US will not succeed in maligning China by rehashing its "lab-leak theory".

"We urge the US to respect science and facts, stop politicizing the issue, stop its intelligence-led and politics-driven origins tracing, and stop undermining … global cooperation on science-based origins tracing," she added.

In another media briefing on March 6, Mao said that China had contributed the most to the global COVID-19 origins-tracing efforts, and called on the US to be more transparent about its suspected early cases and the situations regarding its biolabs worldwide.