GENEVA: WHO experts voiced frustration Saturday over the lack of access to raw data during a recent mission to China to probe the pandemic’s origins, saying more was needed to detect possible early Covid cases.

“We want more data. We have asked for more data,” Peter Ben Embarek, who headed WHO’s expert mission to Wuhan, told AFP in an interview.

“There is a mix of frustration but also a mix of realistic expectations in terms of what is feasible under which time frame,” he said, adding he hoped the requested data would be made available going forward.

The four-week WHO mission to China to uncover the origins of the coronavirus wrapped up earlier this week with no conclusive findings.

Experts believe the disease — which has killed nearly 2.4 million people worldwide — originated in bats and could have been transmitted to humans via another mammal.

But while the virus was first discovered in Wuhan in December 2019, it remains unclear if that is when and where the outbreak actually began.

The expert team determined that there were no signs of large clusters of Covid-19 in Wuhan or elsewhere prior to December that year, but did not rule out sporadic cases spreading before that.

Ben Embarek said the team would have been keen to have access to raw data about earlier cases of illnesses, including pneumonia, flu and fever, that could conceivably have been Covid.

Prior to the mission, Chinese scientists had scanned their systems and identified 72,000 such cases between October and December. They had applied sets of criteria to determine if the cases could possibly be Covid, whittling down the list to just 92 cases worth examining.

Out of which 67 remained available to submit to serological tests. They all came back negative for Covid.

Be Embarek said the team had asked in vain for the specific criteria used.

“We are trying to understand that process of getting from 72,000 down to 92”, he said, saying access to the raw data requested would make it possible to apply “less stringent criteria so we have a larger number to work with.”

“That will be a proposal for studies in the next phase,” he said.

John Watson, a British epidemiologist and a member of the team, acknowledged that there was a “full and frank discussion” about access to the data, but said focusing too much on that aspect would be unfair.

While the team’s Chinese counterparts did not share all the raw data requested, he said, they had shared “enormous detail” about their work, methods and results.

Another team member, Peter Daszak, meanwhile rejected on Tuesday a report that there had been shouting matches between the international team and their Chinese counterparts over data access.

“This was NOT my experience on @WHO mission,” he said in a tweet, adding: “We DID get access to critical new data throughout.”

The team members have had to walk a diplomatic tightrope, with the US urging a “robust” probe and China warning against politicising the issue.