THE WORLD HEALTH ORGANIZATION joint investigation with China into the origins of the coronavirus looked into a dark chasm and saw darkness. The report offers theories about pathways of a zoonotic spillover from animals to people, but not a single animal source among thousands has tested positive with SARS-CoV-2. The investigators did not conduct a forensic probe into the possibility of a laboratory leak. The origins of the pandemic remain obscure. Finding the answer is as important and elusive as ever.

Overshadowing the whole exercise is the unspoken power of the Chinese party-state to determine the outcome. China has strenuously denied that the virus may have leaked from the Wuhan Institute of Virology, which was carrying out risky gain-of-function experiments on bat coronaviruses. This involves modifying viral genomes to give them new properties, including the ability to infect lung cells of laboratory mice that had been genetically changed to respond as human respiratory cells would. According to the WHO-China report, during the team’s visit to the institute on Feb. 3, “rumours of a leak from the laboratory were refuted categorically by the laboratory director.” The director said the laboratory handled some 13,000 samples over three years. “No infection was ever reported.” All staff are tested and the results all negative, he said. A member of the WHO team, Dr. Dominic Dwyer of Australia, told reporters Tuesday, “I think we were satisfied that there was no obvious evidence of a problem.” But he conceded the team had not conducted a forensic investigation of a possible laboratory leak. Will China now permit one? China’s reluctance only fuels suspicions of something to hide.

The joint investigation — 17 Chinese and 17 international scientists working over 28 days in January and February — ran into many frustrating unknowns. In search of clues from early cases in Wuhan, 233 health institutions checked 76,253 health records of respiratory conditions in October and November 2019 and identified 92 that might be SARS-CoV-2. Upon testing, none were. The Huanan food market in Wuhan sold seafood and wild animals, but “no firm conclusion” can be drawn about its role because there were also virus cases with no connection to the market, the report says. Viral genomes and epidemiological data showed “no obvious clustering” by “exposure to raw meat or furry animals.” The report adds, “Through extensive testing of animal products in the Huanan market, no evidence of animal infections was found.” More than 80,000 wildlife, livestock and poultry samples were collected from 31 provinces in China and none tested positive for the virus before or after the outbreak.

The Chinese and WHO scientists insisted the most likely pathway of the virus was a zoonotic spillover, either directly or indirectly from an animal species to humans. They called a laboratory leak “an extremely unlikely pathway.” But the WHO director-general, Dr. Tedros Adhanom Ghebreyesus, disagreed with the team, saying the laboratory leak “requires further investigation.” He declared that all hypotheses remain on the table, and he is ready to deploy specialists to probe further.

China has a responsibility to open its doors. This is not a blame game, but an essential investigation into the cause of this pandemic to make another one less likely.

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