Under the global glare, Beijing delayed access for independent experts into China to probe the origins of the pandemic, reluctant to agree to an inquiry.

But the WHO now says China has granted permission for a visit by its experts, with a 10-person team expected to arrive shortly for a five or six week visit - including a fortnight spent in quarantine.

Chinese authorities this week refused to confirm the exact dates and details of the visit, a sign of the enduring sensitivity of their mission.

COVID-19 was first detected in the central city of Wuhan in late 2019, before seeping beyond China's borders to wreak havoc, costing over 1.8 million lives and eviscerating economies.

But its origins remain bitterly contested, lost in a fog of recriminations and conjecture from the international community - as well as obfuscation from Chinese authorities determined to keep control of its virus narrative.

The WHO team has promised to focus on the science, specifically how the coronavirus jumped from animals - believed to be bats - to humans.

"This is not about finding a guilty country or a guilty authority," Fabian Leendertz from the Robert Koch Institute, Germany's central disease control body who will be among the team to visit, told AFP in late December.

"This is about understanding what happened to avoid that in the future, to reduce the risk."

But doubt has been cast over what the WHO mission can reasonably expect to achieve and the state pressure they will face, raising fears that the mission will serve to rubber stamp China's official story, not challenge it.

The upcoming visit will not be the first time COVID-19 has brought WHO teams to China. A mission last year looked at the response by authorities rather than the virus origins, with another in the summer laying the groundwork for the upcoming probe.

But this time the WHO will wade into a swamp of competing interests, stuck between accusatory Western nations and a Chinese leadership determined to show that its secretive and hierarchical political system served to stem, not spread, the outbreak.

It is unclear who the experts will be able to meet when they arrive in Wuhan to retrace the initial days and weeks of the pandemic.

Inside China, whistleblowers have been silenced and citizen journalists jailed, including a 37-year-old woman imprisoned last week for four years over video reports from the city during its prolonged lockdown.

Outside, responsibility for the virus has been weaponized.

From the outset, US President Donald Trump used the virus as political bludgeon against big power rival China.

He accused Beijing of trying to hide the outbreak of what he dubbed the "China virus" and repeated unsubstantiated rumors it leaked from a Wuhan lab.

Trump then pulled the US out of the WHO, accusing it of going soft on China, a nation with which he was also engaged in a bitter trade war.

Critics say that blizzard of accusations sought to divert attention from Washington's bungled response to a crisis which has so far killed more than 350,000 Americans.

Without them, said one, "a lot of these situations that we had in January 2020 would not have played out the way it did." 

"It is the geopolitics that... put the world in this situation," Ilona Kickbusch, of the Global Health Center at the Graduate Institute of International and Development Studies in Geneva, told AFP.

China has since deftly reframed its version of events, hailing its "extraordinary success" in curbing the pandemic within its borders and rebooting its economy.

Beijing now says it will ride to the rescue of poorer nations, promising cheap vaccines and seeding doubt that the virus even originated in China.

Foreign Minister Wang Yi recently repeated the unproven claim that "that the pandemic likely started in multiple points around the world."

If politics and an unprecedented health crisis continue to be conflated, experts fear deeper losses in the fight against a pandemic which knows no borders.

"There is this world-in-disorder feeling," said Kickbusch. "If the trust goes out of global health, that will make it so, so difficult to cooperate."

In that spirit, the WHO has said its international experts are expected to "augment, rather than duplicate, ongoing or existing efforts" during their upcoming visit to China, meaning it will not probe research already provided by local scientists.

"I am not optimistic. The trail is now cold," said Professor Gregory Gray at Duke University's Division of Infectious Diseases, on the likelihood of the overseas experts tracking the virus' animal origin.

But the trip may not be entirely in vain, he stressed: it may be able to lay the groundwork for "sustainable surveillance" for when future virus outbreaks hit.