Strategies On Molecular Detection Methods And Cycles To Control Of The COVID-19 Epidemic

The molecular testing is the key method to effectively control epidemic transmission.The detection strategies including molecular detection methods and detection frequency are critical to prevent the emerging of different SARS-Co V-2variants with different replication and transmission characters.Since the Omicron BA.2variant was highly infectious and most of the infected were asymptomatic,who could only be isolated through testing.However,large-scale nucleic acid testing required a large amount of medical resources,bringing great challenges to epidemic prevention and control.But widespread use of rapid antigen tests has proved effective in reducing the spread of outbreaks.Therefore,in view of the current development of the epidemic situation in China,it is of great significance to optimize detection measures by exploring the inhibition degree of nucleic acid testing and antigen testing.Taking Omicron BA.2 as an example,we analyzed the prevalence of this mutant in China,considering the sensitivity of different detection methods,accessibility of detection methods and results,dynamic changes of viral load of mutant strains,detection cycle and other factors.First,we described the spatiotemporal distribution of the epidemic in China.Then we established an improved SEIR model at the population level,gave the model regeneration number expression and calculated the infectivity coefficient.We also built a SIQR model based on the viral load curve of infected individuals at the individual level.Finally,with these two models,we assessed the effectiveness of two main molecular diagnostic methods,rapid antigen detection and nucleic acid testing,and different detection frequencies to control the epidemic for different basic reproduction number(R0).By adjusting important parameters,Our results showed that the final improved SEIR model and SIQR model simulation results were consistent,indicating that when the prevalence rate was high(R0 was greater than 3),daily antigen detection could not effectively inhibit the development of the epidemic.When a local pandemic occurs,there may be a delay in reporting nucleic acid test results,even daily nucleic acid testing was not effective in removing infections.In this case,both daily antigen testing and daily nucleic acid testing were effective in reducing infections by only 40% to 65%.While the value of R0 is less than 3(e.g.,under effective public health interventions),daily rapid antigen tests were comparable to daily nucleic acid tests,which could completely inhibit new infections.Under simulated conditions,the infected cases could be eliminated quickly,and the two detection methods can basically eliminate the relative infections within 2 weeks.Our study indicated that the different molecular detection strategies are needed to be adopted regarding the different replication and transmission character of emerging SARS-Co V-2 variants.For variants with a relative higher R0,the daily rapid antigen testing incorporating with the nonpharmaceutical interventions could be an important alternative in case the massive nucleic acid testing could not be performed successively and sample-to-answer turnaround time is delayed.