Picture: 123RF/LIGHTWISE
Picture: 123RF/LIGHTWISE

Singapore/Beijing — There is a real risk of cross-border coronavirus transmission through the $1.5-trillion global agri-food market, according to a scientist who has studied the phenomenon.

It is possible that contaminated food imports can transfer the virus to workers as well as the environment, said Dale Fisher, an infectious diseases physician at Singapore’s National University Hospital. Frozen-food markets are thought to be one harbour in the first part of a chain of transmission, he said.

“It’s hitching a ride on the food, infecting the first person that opens the box,” Fisher, who also chairs the Global Outbreak Alert and Response Network, said. “It’s not to be confused with supermarket shelves getting infected. It’s really at the marketplace, before there’s been a lot of dilution.”

In recent months, China has been vocal about finding traces of the SARS-CoV-2 pathogen on packaging and food, raising fears that imported items are linked to the recent virus resurgence. Beijing has ordered a range of precautionary steps, creating major disruptions with its trading partners.

While such transmission remains a “freakish” event, the scale of the global food trade is such that it will occur a few times out of millions of imports and exports, said Fisher.

‘Two schools’

It’s a theory that has been downplayed by the World Health Organisation (WHO) and some Western nations. The WHO has said that recent evidence of epidemiology shows that it’s “unlikely” that the virus could be transmitted from the surfaces to human respiratory systems, while the US Food and Drug Administration (FDA) has also stated it isn’t aware of any evidence to suggest the disease can spread through food.

Outside China, where authorities are increasingly weighing in the possibility that the virus can be carried and transmitted via food packaging, the theory is barely mentioned or discussed. Fisher is one of the few international experts who studies the seeding of outbreaks in contaminated fresh and frozen food.

It’s because there’s a lot of stainless steel, which it grows on. It’s cold, it’s crowded — it’s noisy so the people have to yell
Dale Fisher, an infectious diseases physician at Singapore’s National University Hospital

“There are two schools of thought and the minority view, which I adhere to, is that there’s a lot of circumstantial evidence,” Fisher said. “A lot of people may be against this because they don’t want to scare the world — the food could be a source.”

Experiments done by Fisher’s team show the coronavirus could survive in the time and temperatures associated with transportation and storage conditions used in the international food trade.

The study published in August showed no weakening of the infectious virus after 21 days at standard food refrigeration and freezing temperatures when the pathogen was added to samples of chicken, salmon and pork.

That the virus tends to thrive in cold and dry environments has made cold-storage facilities ideal spaces for the pathogen to spread. Meatpacking plants and abattoirs, instead of schools and churches, are more likely to be hot spots for Covid-19 outbreaks, according to Fisher.

“It’s because there’s a lot of stainless steel, which it grows on,” he said. “It’s cold, it’s crowded — it’s noisy so the people have to yell.”

China scares

Earlier this month, authorities in the eastern Chinese coastal city of Qingdao said they found live SARS-CoV-2 on imported frozen seafood, with two port workers responsible for unloading the refrigerated packaging testing positive for the virus.

China has said several times in recent months that imported refrigerated goods are risks for reintroducing the coronavirus into the country. It subsequently banned imported products, including seafood from Indonesia and chicken wings from Brazil, following positive tests on shipping containers and food packaging.

A June outbreak in Beijing triggered a nationwide boycott of salmon when the virus was traced to the chopping board of a seller of imported fish. New Zealand, which has maintained long virus-free stretches, also said it is looking at the chance that one of its new clusters could be linked to a cold-storage plant.

Fisher argued that the reason Asian countries are more likely to find evidence of food and packaging transmission is thanks to the now contained nature of outbreaks in many of those countries, unlike those in the West now battling a new wave of infections.

“You’d never pick it up in the US or in Europe, because you only pick it up if you go from zero cases for 100 days, and then have a small cluster,” he said. “You say, well how did this small cluster start?”

To prevent this, food production companies need to ensure workers are vigilant on mask-wearing, hand-washing and regular sanitisation of surfaces and utensils, said Fisher, “And you need to make sure that all these outbreaks in meat processing plants stop.”



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