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Can Frozen Food Spread The Coronavirus?

A health officer in a protective suit collects a sample from a package of imported frozen food for coronavirus rapid test at a wholesale market in China.
Wu Zheng
VCG via Getty Images
A health officer in a protective suit collects a sample from a package of imported frozen food for coronavirus rapid test at a wholesale market in China.

At a news conference this week, the World Health Organization made a surprising statement: The coronavirus could possibly transmit on frozen packages of food.

"We know that the virus can persist and survive in conditions that are found in these cold and frozen environments," says Peter Ben Embarek, the food scientist who led the World Health Organization team that traveled to China to investigate the origin of the pandemic. "But we don't really understand if the virus can then transmit to humans."

Embarek went on to say that scientists need to investigate further this possible route of transmission – and that frozen meat, perhaps frozen wild meat, could have sparked an early outbreak of COVID-19 last year at the Huanan Seafood market in Wuhan.

"There were definitely frozen meat and seafood sheltered at Huanan, some of it probably farmed wildlife," says disease ecologist Peter Daszak, who was also part of WHO's team in China. "But there was a lot else going on at the market, as well." For example, there were also stalls selling fresh seafood and wildlife. And, Daszak says, the outbreak could have started from an infected vendor or customer. "We are keeping every option on the table and trying to keep an open mind about it."

Chinese scientists have linked several outbreaks in the country last year to frozen packages of meat or seafood. In particular, an outbreak in Beijing last summer centered around a massive wholesale market, called Xinfadi Market.

Scientists found live coronavirus on a package of frozen cod fish there. They also found signs of the virus inside the packaging, Daszak says, suggesting the package became contaminated where the frozen food was packed.

"It was a good bit of detective work," Daszak says.

For the outbreak in the Xinfadi Market, Daszak says, people appear to have caught the virus from a surface. "We don't know if that means the virus was introduced that way. And we don't know if that happened at Huanan seafood market. We're still looking at that."

These results – and the statements from WHO — were a bit surprising, because they go against what scientists have been telling us for a few months now. That you catch COVID-19 primarily through the air, not surfaces. And you don't need to wipe down food packages.

So what gives?

First off, this Xinfadi Market is not your local Trader Joe's, says microbiologist Emanuel Goldman at Rutgers New Jersey Medical School. Xinfadi is enormous. It's 12 million square feet — larger than 200 football fields. Inside, workers receive international shipments of large pallets of frozen meat and seafood which they ship to stores across Beijing. The fish isn't in in individually-packaged boxes, like you find in a frozen food section of the grocery store. A giant frozen slab is a very different surface and has very different conditions than a small package of fish sticks. The slab will stay colder for longer, and the virus could survive on it – or in it — longer.

In other words, Goldman says, the environment inside this warehouse is very different from one that a regular consumer would ever find themselves in. So far, only warehouse workers and dock workers, receiving international packages, have been possibly infected through these frozen packages.

"China hasn't had any reports of consumers, of even suspicion, of consumers being infected by this route," Goldman says.

Second, Goldman says, even under these very specific conditions — with industrial-scale shipping — transmission through this route is incredibly rare.

"It's so rare as to be of negligible importance in the real world to most people," he adds. In fact, he says, you'd be more likely to win the lottery than get infected through a frozen package of food. "And it would have to be one of those lotteries with very few winners, like the Publishers Clearinghouse Sweepstakes."

"It's very unlikely that you would get the virus from food," he adds. "SARS-Cov-2 is a virus you get by breathing."

So the original advice stands, Goldman says. You don't need to wipe down your frozen pizza box or wear gloves when you go to buy frozen fish sticks. And if you're still worried about packaging, he says, "Just wash your hands with soap and water."

Copyright 2021 NPR. To see more, visit https://www.npr.org.

Michaeleen Doucleff, PhD, is a correspondent for NPR's Science Desk. For nearly a decade, she has been reporting for the radio and the web for NPR's global health outlet, Goats and Soda. Doucleff focuses on disease outbreaks, cross-cultural parenting, and women and children's health.