On August 20 and 21, 2021, Shanghai reported five confirmed cases of COVID-19 related to Pudong Airport in succession.
Although the momentum of the epidemic has been quickly suppressed, it still makes people’s nerves that have just recovered from the Nanjing Yangzhou epidemic tense again.
How can we continue to respond to the ongoing threat of the epidemic? What factors are the core issues that we focus on in epidemic prevention and control? Will COVID-19 be eradicated like smallpox? In fact, discussions on epidemic prevention and control have been ongoing since the beginning of 2020.
What are we talking about when we are talking about epidemic prevention and control? After fighting against COVID-19 for more than a year, we tried to answer this question again.
We first assume two most extreme possibilities: complete eradication of the virus by humans and abandonment of all resistance by humans.
By connecting these two most extreme possibilities together, the coordinate axis formed can be understood as the different levels of epidemic prevention adopted by humans when facing the epidemic.
What anchor point should we choose on this coordinate segment? It is relatively easy to discuss the left and right endpoints, which are the two most extreme possibilities we hypothesize.
One extreme that can be ruled out first is to give up all resistance.
Although at the beginning of the epidemic, some countries or regions tried to achieve Herd immunity through natural infection, in fact, facing the rapid growth of cases, most countries have more or less implemented some epidemic prevention and control measures.
Recently, the newly emerged Delta mutant strains have brought new variables.
According to a CDC document exposed by the Washington Post, the Basic reproduction number (R0) of Delta mutant is about 5-9.5, which is on a par with chicken pox (about 8-9) in infectious diseases and second only to measles (about 15).
Source: Reference 2, that is to say, if we do not effectively intervene in the prevalence of delta COVID-19, then on average, each delta infected person will spread the virus to 5 to 8 close contacts who have no immunity to the virus.
By contrast, the R0 of the original COVID-19 strain evaluated by CDC before is 2, which is equivalent to the Common cold.
If you want to Eradication of infectious diseases through Herd immunity, the population needs to achieve an immunization rate of 1-1/R0.
According to the CDC evaluation, the R0 is approximately 5-9.5, and the population immunity rate needs to reach nearly 90%.
Let’s take a look at eradication first.
Looking back at the history of human response to viruses, the most successful battle is the eradication of smallpox