The coronavirus pandemic may have originated in a pig’s head, authorities investigating the original Wuhan outbreak say.
Beijing has suspended imports of frozen food products after evidence suggested the original Sars-CoV-2 virus may have arrived at the Huanan Seafood Wholesale Market this way.
Chinese health authorities have repeatedly reported finding the Covid-19 virus on frozen food including pig heads and seafood, both products likely to have been sold at Huanan Market.
The “cold-chain transmission” theory was discussed prominently at a press conference in Wuhan on Tuesday, where an international team of scientists from the World Health Organisation (WHO) presented the findings of their month-long probe.
“Sars-CoV-2 can persist in conditions found in frozen food, packaging and cold-chain products,” National Health Commission official Liang Wannian said.
If proven true this would support China’s theory that coronavirus originated outside of Wuhan and had already infected humans before the December 2019 infection that kickstarted the global pandemic.
In June, Beijing suffered its first Covid-19 outbreak in 55 days at a wholesale food market, baffling investigators — until they discovered genetic similarities between the infections and viral remnants on imported frozen salmon.
Chinese authorities went on to link several more outbreaks to imported food, including a November incident involving pig heads imported from North America.
Officials found that two workers in port city Tianjin had been infected with coronavirus via the animal heads, after finding genetically similar virus remnants on the ground where the heads had accidentally been dropped.
However local health authorities did not say whether the heads themselves had tested positive for the virus.
Virus researchers in other parts of the world have ruled the chances are low of a worker becoming infected by handling a package that had been sneezed or coughed on by a sick person in another country, but it is possible.
At Tuesday’s press conference Daniel Lucey, an infectious disease specialist at Georgetown University Medical Centre in the US said the frozen food theory didn’t seem like a “very likely legitimate explanation” and would require comparative studies to be proven.
“Of all the seafood markets in China and Asia and around the world how did the cold-chain packaging end up causing an outbreak in Wuhan first?” he asked.
But Dale Fisher, an infectious diseases doctor at the National University of Singapore, said it was “reasonable” for the WHO team to consider the theory.
“The cold-chain [transmission] theory really comes on the idea that there are outbreaks happening in the meat processing plants in another country,” he said.
“But it’s very unlikely there was a widespread disease spread happening before Wuhan.”
The WHO team said the prevailing theory that the virus leapt to humans from an intermediary animal remains the most likely but further research into the cold-chain theory is warranted.
This theory that coronavirus leaked from the Wuhan Institute of Virology was “extremely unlikely”, they added.