But small, scattered gatherings continued to emerge, despite some of the world’s strict border restrictions and quarantine measures.
Aside from incoming travelers, Chinese officials suspect the virus came from another culprit – the import of frozen food.
But China claims it has proven that it is possible to contract Covid-19 from food packaging and is redoubling its efforts to prevent it.
Jin Dongyan, a professor of virology at the University of Hong Kong, said that while there is such a possibility, the CDC has not provided strong evidence of transmission. He said workers may have contracted the virus from elsewhere and then contaminated food packages. The missing step, he said, would be to compare the genetic sequences of the virus in Qingdao workers and people who have handled food at the import source.
“Every virus has its own markers. If they match, then we can say there is a chain of evidence,” he said.
This week, Chinese authorities tightened measures again, after a worker at a frozen food company in the coastal city of Tianjin tested positive for the virus at the end of last week.
The Chinese government announced, Monday, that all shipments of refrigerated and frozen food imports must be disinfected before they can enter the market. The requirement includes both the inner and outer packaging of these products, and the vehicles used to transport them.
“We will seriously implement preventive disinfection of cold chain food imports at ports of entry and strengthen inter-agency cooperation to stop importing Covid-19 through cold chain food products,” Bi Kexin, a senior official in charge of food safety in the General Administration of Customs, said at a press conference Thursday.
The extraordinary procedures are in addition to the comprehensive examination that has already been introduced.
As of Thursday, Chinese customs said it had stopped imports from 99 food companies across 20 countries as foreign factory workers were said to have contracted Covid-19.
Meanwhile, customs authorities across China have stepped up coronavirus tests on imports of frozen food, especially seafood. As of Thursday, they had conducted randomized screening checks on nearly 873,000 samples, of which 13 were said to be positive.
Blame the imports
China became suspicious of importing frozen food after the outbreak of the disease from Beijing’s largest wholesale food market in June.
Wu did not explain how he came to this conclusion, but Chinese scientists and other health officials have also cited the import of frozen seafood as the possible cause of the outbreak.
Jin, a virologist from the University of Hong Kong, remains skeptical. “This is a very weak paper. Nothing can be said from the study,” he said.
Is it possible to catch Covid-19 from food or packaging?
Coronavirus is spread mostly from person to person via respiratory droplets when an infected person coughs, sneezes or talks. While it is technically possible to catch Covid-19 from food or packaging, experts say it requires the convergence of a series of low-probability events.
First, the infected worker will need to contaminate the food or its packaging with a viral load high enough to cause an infection – perhaps by sneezing, coughing, or yelling at it without a face mask.
Then, the virus must survive a long international cargo flight and remain active on the surface while it waits to be unloaded and unloaded. From there, a food processor on the receiving end will have to touch the virus before it touches its nose or mouth to become infected.
Previous studies have shown that the viability of the new Corona virus varies from hours to weeks, depending on a number of factors, including temperature, humidity and the type of surface it is on.
The ‘zero tolerance’ approach
Dale Fisher, an infectious disease specialist at the National University of Singapore, is studying how long the new coronavirus can live on chilled and frozen meats and salmon. His findings will be used to assess the potential for disease outbreaks resulting from food imports.
He said Workers on the receiving end of food shipments should practice good hygiene by keeping their work surfaces clean and washing their hands frequently. But he does not believe that consumers are at risk of contracting the virus from frozen or chilled food packages, because every time the product is moved or touched, the virus is diluted.
“Because if it is not uncommon for those who handle food early, then down the list, when it is brushed, wiped, moved, placed on a shelf and moved to another shelf … consumers).
Fisher said that in most countries, even if imported frozen foods strike a food processor, they will not be noticed due to the large number of active cases. “You will only notice it in countries that have no cases,” he said.
On the other hand, China has doubled down on overseas shipments. But Fischer said that the widespread testing China is publishing may not apply to other countries where infections are common.
“It is clear that in the United States and Europe, there will be no benefit at all in food testing, because there are a lot of cases that people are spreading,” he said. But China does not really tolerate Covid-19.
“When there are trillions of tons of food moving around the world, even an unexpected event will happen multiple times.”
But even if there is such a risk, there is no need to ban food imports, according to Fisher.
He said: “The intervention is only to ensure that the food source has obtained safe measures from Covid so that the food does not become contaminated.” “We’re not saying stop sending food around the world.”