- The definitions about infection sources and the theoretical basis of "object-to-human transmission" for SARS-CoV-2
|Author :||LI Jingbo, ZHANG Tong-yang, LI Yong-qiang, TONG Yi-gang|
To explore whether objects and environment contaminated by pathogens can be identified as infection sources, and to analyze the theoretical basis of “object-to-human transmission” for SARS-CoV-2.
Differences in the definition of infection sources between Chinese and Western academics are analyzed. Examples of “environment-to-human transmission” and “object-to-human transmission” for viral infectious diseases such as hepatitis A, avian influenza and severe acute respiratory syndrome (SARS) were reviewed. The basic theory and know-ledge of life science were applied to analyze various cases of SARS-CoV-2 transmission via multiple channels such as “imported cold chain” “border trade or port operation” “international mail”, etc. encountered in SARS-CoV-2 infection prevention and control effort of China.
It is clarified that the definition about infection sources in China is rigorous, emphasizing the proliferation, and only human and animal infected by pathogens can be recognized as infection source, while the Western definitions are broader, emphasizing infectivity, objects and environment contaminated by pathogens can also be identified as infection source. Through theoretical analysis and various examples, it is confirmed that SARS-CoV-2 can survive in normal temperature environment for several days, extends to several months under cryogenic condition. The objects contaminated by SARS-CoV-2 can cause indirect contact infection. However, the probability of “object-to-human transmission” is relatively lower. Conclusion Definitions about infection sources in China is rigorous, scientific, and practical, and has formed a convention in the prevention and control of infectious diseases. Therefore, there is no need to amend the definition. With popularizing nucleic acid test, the goal of screening for viral infectious diseases such as COVID-19 can be converted from “quickly finding sources of infection” to “quickly seeking sources of the virus”, including viruses in environment. Understanding the theoretical basis of “object-to-human transmission”, the necessity of positive strategies such as “preventing the transmission from both sources of human and objects” would be fully comprehended.