A Chinese Center for Disease Control and Prevention worker swabs frozen fish for coronavirus testing at the Wandong market in Guiyang, in the southwestern Guizhou province, on July 1, 2020. Image: AFP

Chinese state media is advancing a possible alternative explanation for the origin of the Covid-19 pandemic, one that claims that the contagion may have first arrived in China from abroad in imported frozen foods. 

Chinese officials quoted in the reports suggest “cold chain food contamination” could debunk the widely held belief that the novel coronavirus first emerged from a wet market in the Chinese city of Wuhan, from where it reputedly made its lethal global spread.  

Experts at China’s National Center for Disease Control and Prevention have said that recent smaller, quickly contained outbreaks of the disease in Beijing, Dalian, Qingdao and even Wuhan have likely arrived from overseas in frozen meat including salmon and chicken. 

The contaminated frozen food theory was first raised after a cluster of Covid-19 infections was discovered and quickly contained in June at the sprawling Xinfadi food distribution market in Beijing. 

Health inspectors check frozen food at a supermarket in Beijing. Photo: Xinhua

Wu Zunyou, the CDC’s chief epidemiologist, was quoted in the Communist Party-run Global Times saying that he and his colleagues were convinced that the Beijing and other outbreaks across the country had came from abroad and that their research could put a “new perspective” on the pandemic’s origin. 

“We have realized that the locally-transmitted cases at Beijing’s Xinfadi market as well as in markets and communities in Dalian and Qingdao throughout the recent months are all linked to the virus found on the packaging of imported frozen food sold in these places,” Wu said in the report. 

“Then we wonder if the eruption at Wuhan’s Huanan market last December could have anything to do with imported food as well… This can be a new clue in our continued epidemiological investigations,” he said.

Chinese CDC experts say the coronavirus may remain latent in contaminated food during cold chain processing, storage and transportation from one location to another at standard temperatures of -18 °C or lower. 

Critics of the theory, however, say that China has a big incentive to advance an alternative theory on the pandemic’s origin as criticism mounts to China’s initial response and cover-up of the outbreak. 

The United States, Australia and other Western nations have all called for an independent international probe into the disease’s first discovery in Wuhan at the end of December, 2019, calls Beijing has so far shunned.

The New York Times reported that World Health Organization (WHO) experts were not allowed access to the Wuhan wet market where the disease is believed to have originated during a visit to China in mid-February.

They apparently agreed not to criticize China’s response so as to be allowed entry to the country. No progress has been made since in unraveling the virus’s origin or how it may have jumped from animals to humans – both key, the WHO says, to prevent another similar outbreak in the future. 

The WHO’s current advisory on Covid-19 and food safety states that “coronaviruses cannot multiply in food – they need a live animal or human host to multiply and survive.” The advisory says “it is not necessary to disinfect food packaging materials.”     

But Chinese authorities are now challenging that wisdom through a new transmission theory. A research paper that appeared in the October issue of China’s National Science Review, a state-backed English scientific journal, elaborates on this “cold chain food contamination” hypothesis. 

The paper’s co-authors, including scientists from the top-flight Tsinghua University, Peking University, Beijing’s Municipal CDC, the Chinese Academy of Medical Sciences’ Institute of Medical Biology and the Chinese Academy of Science’ Beijing Institute of Genomics, say their research conducted nucleic acid and virus genome sequencing tests on contaminated frozen food.

The paper cited Yang Zhanqiu, a professor with the University of Wuhan’s Institute of Virology, raising the possibility that the virus may have arrived at Wuhan’s Huanan market from outside China. 

The Huanan market is the largest seafood wholesale market in Wuhan and across central China, and hosts a cluster of stalls with imported seafood and meat products from Thailand, the Philippines, Brazil and other foreign countries, Yang said. 

The Huanan Seafood Market in Wuhan is believed to be the initial epicenter of the Covid-19 outbreak, but there have been an alternative theory suggesting the virus could have been brought to the market in contaminated frozen food sold there. Photo: RTHK

Wu Guizhen, the Chinesse CDC’s chief biosafety expert, doubled down on the theory during a separate China Central Television interview where she said that perhaps it was time to “take a new tack” in investigations into the virus’s origins.

“One clue .. is indeed Beijing’s Xinfadi market itself, as the market did not process raw meat or trade wildlife at all,” Wu said. “Questions are being raised if the source could indeed be an infected asymptomatic carrier or contaminated frozen food from somewhere else, and the environment at the market there only facilitated the incubation and spread of the virus… This could be the same with Wuhan’s Huanan market,” said Wu.  

Critics of the new Covid-19 transmission theory say it is not clear that the cited research has been peer-reviewed in any scientifically, credibile manner and that the authors did not specify the details of their data or its sources. 

Bruce Lee, a professor of health policy and management at the City University of New York’s School of Public Health, noted in an article that the recent claims made by China’s CDC did not cite how their related testing was done. 

“One or a few viruses are not enough to cause a commotion. There has to be enough of the live virus around (an infectious dose) to lead to an infection. This infectious dose would have to be able to stay on the packaging long enough as well,” said Lee.

Ryan Clarke, a senior research fellow at the National University of Singapore’s East Asian Institute, is similarly skeptical of the Chinese findings.

He told Asia Times that China’s claim about Covid-19 being imported into Wuhan in late 2019 via international food supply chains was “absurd” and aimed to “shift focus away” from the study of bats in China, one likely source of the virus. 

“Covid-19 is a bat coronavirus that likely originates from a unique bat species that’s found in Yunnan and other nearby areas of southwest China and northeast India,” said Clarke. 

“The only fundamental point of origin question is whether this Covid-19-causing bat coronavirus made the species jump into humans from a natural reservoir or whether it was leaked intentionally or not from a lab where bat coronavirus bionengineering experiments had been conducted,” he said, citing the Wuhan Institute of Virology of the Chinese Academy of Sciences.

“I think people can connect the dots for themselves. This didn’t come from frozen Norwegian salmon or Brazilian chicken,” said Clarke, who previously held epidemiological intelligence and public health positions at Deutsche Bank, the Oxford University and Singapore’s National University Hospital.

The US CDC has maintained on its website that “respiratory droplets can also land on surfaces and objects” and that it is “possible that a person could get Covid-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or eyes.” 

New Zealand’s government has reputedly investigated the possibility that contamination of frozen foods may have been the source of an outbreak in August.

Qingdao’s CDC has said it has detected and isolated live virus from the packaging of imported frozen cod while contact-tracing an outbreak in the city in October.

China’s General Administration of Customs announced last week a one-week suspension of imported seafood products from an Ecuadorian producer after detection of the virus on a consignment of frozen silvery pomfrets. More Chinese food import bans could follow if the theory gains traction or credibility, analysts say.

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