Coronavirus stays viable on chilled food for 3 weeks, but risk of getting infected very low

SINGAPORE - It is possible to get Covid-19 from contaminated imported chilled or frozen food, but the risk is very low, said experts.

The coronavirus that causes Covid-19 remains viable for at least three weeks at 4 deg C, said Professor Dale Fisher, a senior consultant in the division of infectious diseases at the National University Hospital.

He recently concluded a study that involved putting the Sars-CoV-2 virus on prawn, salmon and pork, and testing its viability after three weeks - an ample time frame for such food to be exported and sold, Prof Fisher said.

Transmission through imported food has become a hot topic following the re-emergence of Covid-19 in New Zealand after 102 days with no cases, leading to a 12-day a lockdown of the city of Auckland.

Four of the people infected work at a refrigerator storage facility, raising the possibility that they may have contracted the disease from the imported food before spreading it to others.

China recently reported finding the virus on frozen chicken wings from Brazil, where the pandemic is raging, and on the outer packaging of frozen prawns from Ecuador.

In June, it said the virus was found in a Beijing market on a chopping board used to cut imported salmon. There was a cluster of more than 200 cases linked to the market.

Prof Ooi Eng Eong, deputy director of Duke-NUS Medical School's Emerging Infectious Diseases Programme, said: "My sense is that although it is certainly possible for CoV-2 to be transmitted through improperly handled food, the risk is likely to be small."

He explained that internationally accepted minimum standards for handling food to prevent transmission of pathogens would also prevent the transmission of this virus.

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Associate Professor Hsu Liyang, an infectious diseases doctor at the NUS Saw Swee Hock School of Public Health, said: "The probability (of infection from handling food) is infinitesimally small. The likelihood of being infected by another asymptomatic or mildly symptomatic person is far, far higher."

Associate Professor Alex Cook, vice-dean of research at the school, said his bet is on infected people here catching it from someone else rather than from imported food, since there is hidden reservoir of the virus here.

The Singapore Food Agency said it is monitoring developments closely and will take the necessary actions to safeguard food safety here, though there is no evidence to show the virus can be transmitted to people from food or food packaging.

It added: “In general, contact with food or food packaging and equipment is no different from contact with other non-food packaging and the environment, for example, common touch surfaces such as lift buttons, door knobs, etc.”

While agreeing that the risk is low, Prof Fisher said: "It's about seeding it to one person, and then human-to-human (transmission) takes over again.

"We know food processing plants host clusters, so it's likely food becomes contaminated. We know the virus can survive the time and temperatures for the trip."

Prof Teo Yik Ying, dean of the school, said the risk to the average consumer is extremely low, but may be higher for people working in the chilled food plants handling imported products every day.

"But even for something where the chance is very small, when multiplied across the total number of chilled packages being shipped between locations, a few events will occur over time," he said.

Prof Fisher added that if infection from handling food has "happened a handful of times, then it fits with the concept of unlikely and not common", but does not make it impossible.

So he reminds people to "wash hands and cook their food well", adding that "the first person to take the frozen or refrigerated meat out of the box and then touch his mouth" could become a new index case.

Prof Ooi also said: "The emphasis should be that proper food hygiene matters both in food centres and at home to prevent common food-borne pathogens.

"The same hygiene standards should also protect the public from Covid-19, even in the event that the raw food is contaminated with CoV-2."

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This article was first published in The Straits Times. Permission required for reproduction.