Disease control workers collecting samples from cold packaging in Qingdao, Shandong province on Sept 26, 2020. (PHOTO PROVIDED TO CHINA DAILY)
The novel coronavirus can spread through frozen food products and concerted global efforts are needed to prevent cold chain transmission and step up information sharing in the field, a report released by Chinese researchers on Tuesday said.
The conclusion was based on epidemiological evidence related to two infected dock workers in the coastal city of Qingdao, Shandong province, who were identified in September during routine testing. That included the genetic sequencing of throat and environmental samples.
The defining piece of evidence was that traces of live virus had been detected on frozen cod packaging that had been handled by the workers, the first time in the world living novel coronavirus was isolated from food packaging, the report said.
It said the study confirmed that the imported cold chain products were contaminated with relatively high loads of SARS-CoV-2 through cold chain processing and fishing, and "the virus can spread across countries and regions over long distances through the international marine fishery trade".
Disease control workers collecting samples from cold packaging in Qingdao, Shandong province on Sept 26, 2020. (PHOTO PROVIDED TO CHINA DAILY)
The report was published online by China CDC Weekly, an academic platform established by the Chinese Center for Disease Control and Prevention.
Research indicated that the novel coronavirus on contaminated products could remain infectious after months or even years in cold storage, leading to what the report called the risk of the "silent transmission of a relatively old virus "for those coming into close contact.
In the case of the two Qingdao dock workers, the longest recorded survival period for the virus was two months.
The report suggested strengthening management of the global cold chain industry, including the processing of frozen fish and meat.
"This may be a hidden route of transmission due to the long-distance transportation of cold-chain seafood products found to be infectious," it said.
Meanwhile, people deemed at high risk of contracting the virus, especially workers engaged in port operations and seafood processing, should undergo regular testing in order to detect possible infections as early as possible.
Disease control workers collecting samples from cold packaging in Qingdao, Shandong province on Sept 26, 2020. (PHOTO PROVIDED TO CHINA DAILY)
The report added that the two workers had both taken off their masks to smoke, and that none of the other workers, who had kept their masks on, were infected, suggesting that proper personal protection measures are vital.
It called for conducting more research into the virus' ability to survive in humid, cold and high-saline environments.
It also noted that the chance of getting infected from frequent exposure to contaminated products was relatively low, and that no consumers had been reported to have contracted the virus due to contact with food products.
"The international community should pay close attention to the SARS-CoV-2 transmission mode through the cold chain, build cooperative international efforts, and share relevant data," it said.
The role of cold chain products in aiding the spread of the virus has been examined and debated by researchers around the world for quite a long time after several domestic outbreaks in China were found to be linked to contaminated imports.
During a study earlier this year into the virus' origin, which was convened by the World Health Organization, international experts suggested that cold chain transmission may have been one of the ways the virus was first introduced into the human population, and that more effort should be devoted to understanding the involvement of cold chain and frozen food products in the virus' origin.
