Covid-19 first broke out in Wuhan, the capital city of Hubei Province in central China in late 2019 and most of the early cases were found at a seafood wholesale market where most goods were sold frozen.
When there was another Covid-19 resurgence in mid-2020 in Beijing, the source was linked to a wholesale agriculture market.
After several months of investigations, researchers studying the origins of Covid-19 concluded that imported food via cold chain from high-risk areas overseas may be the origin of the resurgence.
These researchers warned that the virus could be reintroduced via cold-chain transportation of contaminated items and initiate an outbreak.
Such a possibility that human transmission of Covid-19 is found in a cold-chain environment, is worrying considering global trade, where goods are exchanged on a large scale around the world, necessitating the need for more investigation on such.
In a joint report by the World Health Organisation (WHO) and China released in March this year, on the origins of Covid-19, introduction through cold or food chain products is listed as a “possible” pathway.
In October, China detected and isolated live Covid-19 in a package of imported frozen cod (fish) during a trace-back investigation into the outbreak in Qingdao in eastern Shandong Province.
This was the first time that live virus was isolated from cold-chain food packaging, which further confirmed that the coronavirus can survive on packaging for a long time during cold-chain transportation, signalling the virus could be carried over long distances across borders.
It was also reported that other port cities in China such as Tianjin and Dalian also experienced coronavirus transmission traced back to imported cold-chain food.
The WHO-China joint report reported that the virus “has been found to persist in frozen food, packaging and cold-chain products,” after the supply chains to Huanan market included cold-chain products and animal products from 20 countries, including those where samples have been reported as positive for Covid-19.
The WHO-China report also indicated that the first cases of Covid-19 in recent outbreaks in China were linked to the cold chain, as the virus was found on packages and products from other countries that supply China with cold-chain products.
In July, press reports quoted the Director of the National Centre for Respiratory Medicine, Wang Chen, who noted that the cold chain in infectious pathways for respiratory disease is a new phenomenon that deserved attention.
Wang said infected people were exposed to the cold chain without other possible sources of the virus while in terms of epidemiology, associations were found between the cold chain and the Covid-19 cases, which could be seen from Covid-19 flare-ups in Beijing’s Xinfadi market and Qingdao.
He noted that during an outbreak in Qingdao, the RNA of the Covid-19 virus was detected on the surface of cold-chain goods and the virus was isolated, proving the fact that living viruses existed on the surface of cold-chain goods.
Wang said there is circumstantial evidence for the exploration of the scientific issue, which is that the Covid-19 virus could survive and remain infectious for a longer period in a cold and relatively dry environment.
This prompted experts that cold-chain exports should be one of the focuses in the second-phase study of Covid-19 origins by WHO.
Leader of the Chinese side under the China-WHO joint team, Liang Wannian, was cited in press reports saying tracing the origins of the new coronavirus responsible for the ongoing pandemic should be directed at countries where the virus had been found in animals, the environment and human samples earlier than the Wuhan outbreak in 2019.
Wannian noted the investigation should also take in countries that exported cold-chain products to China’s Huanan Seafood Market.