Global health experts investigating the origins of the coronavirus have met in the Chinese city where it was first reported to reveal their findings.
At a World Health Organisation (WHO) conference in Wuhan on Tuesday, experts revealed new information about the virus, which is responsible for an ongoing global pandemic costing more than 2.3m lives.
The team arrived in Wuhan on January 14 and, after two weeks of quarantine, visited key sites including the Huanan seafood market, the location of the first known cluster of infections, and the Wuhan Institute of Virology.
Many believed the virus to have originated in bats before being passed to humans through another species of wild animal, such as a pangolin or bamboo rat.
This is what we have learned so far:
1. ‘Very unlikely’ to be a lab incident
The team visited the Wuhan Institute of Virology, the subject of a number of conspiracy theories that claim a lab leak caused the city’s outbreak, and concluded it was “very unlikely” that this was the case.
Former US president Donald Trump claimed to have “evidence” of such an event, though the WHO dismissed his comments as “speculative”.
Nor does the theory explain the virus’s introduction into the human population – and it will it not be suggested as an avenue to investigate further. China has always strongly rejected that possibility.
2. Origins in bats
Peter Ben Embarek, a WHO virus expert, said that work to identify the origins of the coronavirus points to a “natural reservoir” in bats, but it is unlikely that they were in Wuhan, the central Chinese city where the outbreak was discovered in late 2019.
“From samples taken from bats in Hubei province, we did not find any evidence of the coronavirus or related viruses. Up until now, we have also not found any existence of coronavirus from samples taken from other wild animals in other parts of China,” Liang Wannian, an expert with China’s Health Commission, added.
This means an “intermediary host species” is yet to be identified, said Embarek.
3. No evidence of virus before December 2019
The virus could have been circulating in other regions of China before it was identified in Wuhan in December 2019, but there was no substantial spread of it before then, Wannian said.
“Based on the research on data from different countries, we discovered that the circulation of Covid-19 could have been earlier than the earliest reported case, by a few weeks,” he said.
4. Wuhan seafood market was not where it started
While the Huanan seafood market is closely linked to the outbreak, Wannian has suggested the first cases were not linked to it.
“Huanan market may not be the first place that had the outbreak and it is not the place that witnessed the earliest case either,” he said.
He added: “The onset date of the first case in this research was in December 8, 2019. The earliest case associated with Hunan seafood market was December 12. The case with the onset on December 8 had no link to Huanan Market.
“Huanan Market may have been a major point of transmission for the virus, but at the same time, it seems that other parts of Wuhan might have also existed within the line of transmission.”
5. Cold-chain transmission a possibility
Embarek, who is a specialist in animal diseases, said that cold-chain transmission of the virus is a possibility which warrants further investigation.
“Cold chain” refers to the transport and trade of frozen food. China has pushed the idea that the virus can be transmitted by frozen food and has repeatedly announced findings of coronavirus traces on imported food packaging.
Embarek said: “We know the virus can survive in conditions that are found in these cold, frozen environments, but we don’t really understand if the virus can transmit to humans.”
He said it would be worthwhile to explore whether a frozen wild animal in a market setting with the right conditions could be conducive to rapid spread of the virus.
Beijing has long blamed frozen-food imports as one cause of a string of outbreaks, introducing mandatory testing and disinfection of foreign goods and saying it found traces of the virus on packaging of products including Brazilian beef, Saudi shrimp and American pork. Elsewhere, experts have been sceptical of the claims with the US Centres for Disease Control stating there is “no evidence” for them.
Another team member, infectious disease expert Dominic Dwyer, said it would probably take years to fully understand the origins of Covid-19.