HONG KONG — The World Health Organization has urged China to share data to help understand the origins of Covid-19, five years on from the start of the pandemic in the Chinese city of Wuhan.

On December 31, 2019, the WHO’s China office noted a cluster of “pneumonia” cases in a statement from health authorities in Wuhan. More than three weeks later, Chinese authorities locked down the city of 11 million.

Fears of a rapidly spreading virus gripped the nation, but – as authorities would later learn - the coronavirus had already spread far beyond China.

While much of the world has moved on from the pandemic lockdowns and restrictions, many questions remain about the source of a virus that killed at least seven million people, crippled healthcare systems and upended the global economy. And many experts say China’s opacity has made finding answers to the pandemic’s origins harder.

“We continue to call on China to share data and access so we can understand the origins of COVID-19. This is a moral and scientific imperative,” the WHO said in a statement on Monday.

“Without transparency, sharing, and cooperation among countries, the world cannot adequately prevent and prepare for future epidemics and pandemics.”

How the pandemic started has been a subject of intense scientific scrutiny as well as heated political debates, with opinions divided primarily over whether it originated from a natural animal spillover or a lab leak.

Many scientists believe the virus originated in the wild, before it jumped from infected animals to humans and spread through a wet market in Wuhan, though they haven’t been able to identify the intermediate host.

Suspicions that the coronavirus was leaked from a laboratory near the market, which was first dismissed as a conspiracy theory, have persisted and been endorsed by some researchers.

The search for the origins of the virus has been hugely controversial from the onset and a key source of political tension. The United States and other Western countries have repeatedly accused China of withholding access to original and complete data – which Beijing has vehemently denied.

WHO officials have also criticized China’s tight control of data access, with one official calling its lack of data disclosure “simply inexcusable” in 2023.

Chinese disease control officials responded at the time, saying China had provided the WHO’s expert group with all information it had on the origins of the virus “without withholding any cases, samples, or their testing and analysis results.”

For years, the global health agency has sought access to test results from workers at the market, as well as other raw data that China collected early on in the pandemic.

It was only in 2023, three years after the start of the pandemic, that WHO got access to certain data that Chinese scientists had gathered in early 2020 at the Huanan Seafood Market in Wuhan. The raw genetic sequences from the samples had been uploaded to the data-sharing site GISAID. They were soon removed, but quick-thinking researchers had already noticed them and downloaded them for further study.

An analysis of that material, published in the peer-reviewed journal Cell in September, showed that coronavirus-susceptible animals and the coronavirus that causes Covid-19 were present at a specific section of the market, although the study did not confirm whether the animals themselves were infected with the virus.

In its statement on Monday, the WHO recounted how on December 31, 2019, its country office in China picked up a statement from the Wuhan municipal health commission’s website on cases of “viral pneumonia” in the city.

“In the weeks, months and years that unfolded after that, COVID-19 came to shape our lives and our world,” it said.

“As we mark this milestone, let’s take a moment to honour the lives changed and lost, recognize those who are suffering from COVID-19 and long COVID, express gratitude to the health workers who sacrificed so much to care for us, and commit to learning from COVID-19 to build a healthier tomorrow.” — CNN