Reuters reports that China has detected the presence of the SARS-CoV-2 virus on packaging for German pork knuckles and Ecuadorian shrimp. China imposed import bans as a result, disrupting trade flows.

As part of more drastic measures used to control the spread of the novel coronavirus, China has tightened restrictions requiring "full coverage" testing and disinfection of imported food products, following a smattering of positive samples detected on beef, pork and seafood.

The country has suspended imports of 99 suppliers from 20 countries, the National Health Commission said on Thursday 12 November.

Beijing argues that such measures are needed prevent the import of the virus, which has been largely contained domestically. A seafood market in the central city of Wuhan is widely believed to be the origin of the pandemic that emerged late last year and has now killed more than 1.25 million people.

The clampdown has caused upheaval in parts of China's cold chain logistics network and sparked grumbling among diplomats in Beijing that the effort is politically driven, with critics saying the measures are costly and unnecessary.

Last week, cold chain facilities in the northern port city of Tianjin were shuttered when a 38-year-old frozen food worker who tested positive for the virus was linked to a 28.1 tonne shipment of frozen German pork knuckles.

"We can't import any seafood as our warehouses have not finished rectification work yet," said an importer in Henan province who manages logistics for imported seafood and fruit.

"It started in October and it has been over a month now and I don't expect it would be finished by the end of the year," said the importer, asking not to be identified.

While scientists say that chances of infection from frozen food are low, Chinese authorities say two dock workers in Qingdao caught the virus last month from the packaging of frozen cod - an assertion that some experts have questioned.

Aiming for “complete elimination”

Outside China, frozen foods are rarely implicated in virus tracing efforts. In August, a New Zealand cold storage worker tested positive, but frozen food was later ruled out as the source by health authorities.

Scientists have pointed out that the tests on cold-chain foods and packaging also detect dead fragments of the virus, meaning that positive results do not indicate the disease is viable and can infect humans.

"People should not fear food, food packaging or delivery of food," Mike Ryan, head of the WHO's emergencies programme said in August. "There is no evidence the food chain is participating in transmission of this virus."

That advice hasn't deterred authorities in China, where there is a surplus of testing equipment and food processing hubs and markets have been a recurrent vector for reported outbreaks.

China's tightened cold chain guidelines call for "complete elimination" and "strict refusal of entry" of any products suspected of contact with the virus.

The rules require routine disinfection, including of inner and outer packaging, and blanket testing of imported goods. Already, exporters whose products tested positive faced a week-long ban, extended to a month for three-time offenders.

"If it's contaminated they return the whole of the food packaging. That's their right, but I don't think that's very necessary. A decontamination process is already sufficient", said Jin Dong-Yan, a virology professor at the University of Hong Kong.

Import hubs including Beijing and Guangzhou have urged companies to halt imports from countries that are severely affected by the outbreak.

A diplomat in Beijing who did not want to be identified given the sensitivity of the matter said they believed China's campaign is political.

"In China authorities have managed to bring it under control but foreign health authorities haven’t, and it shows the problems in governance abroad," the diplomat said.

Positive tests from seafood and meat products have sparked public fear about imported food.

"The pandemic is raging overseas, so it's better for authorities to be strict with these rules," said the Henan importer.

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