China Daily:

According to the WHO expert team for origin tracing of SARS-CoV-2 this February, COVID-19 introduction through an intermediate host is "likely-to-very-likely", and introduction through cold chain products is "possible." What's your take on that? Thanks. 

Wang Chen:

The role the cold chain plays in spreading infectious diseases is a new phenomenon. I am an expert in respiratory diseases. Respiratory infectious diseases are a dominant type of infectious diseases. The transmission route of respiratory viruses, including the cold chain, is indeed a new phenomenon that deserves our full attention. In summary, first, in terms of epidemiology, we have found associations between the cold chain and the disease. That is to say, through epidemiological investigations, we found that the possible cause of some COVID-19 infections could be traced to touching the surface of cold chain products. The close associations can be seen from the COVID-19 flare-ups in Beijing's Xinfadi Market and Qingdao. The infected people were exposed to the cold chain, and no other possible sources of the virus were since found, except the cold chain.

Second, in terms of detection of the nucleic acid of the virus, positive results have been found on cold chain goods. During the outbreak in Qingdao, in particular, the RNA of SARS-CoV-2 was detected on the surface of cold chain goods, and the virus was isolated and cultured, proving the fact that living virus existed on the surface of cold chain goods. Given the two points above, the chain of evidence has become complete. Moreover, there is a circumstantial evidence for the exploration of the scientific issue, which is that the virus can survive and remain infectious for a longer period in a cold and relatively dry environment. It can even survive for 21 days in winter. Therefore, when the virus emerges in a place, and if the cold chain products get the virus, the virus can be transmitted from one place to another in a low temperature during transportation, leading to cross-regional transmission accordingly. The cold chain transmission is a new feature that we have found in the COVID-19 pandemic, which is worthy of attention, and the chain of evidence for the transmission has become relatively complete.

To further trace origins of the virus, we suggest that the cold chain should be taken as a key clue. Given the circumstances of international trade, with the exchange of people and goods around the world, the items-to-human transmission in the cold chain environment has made pathogen transmission more complicated, which is particularly worthy of investigation and studies.