The Defense of Shangri-La: A Thought Experiment of Periodic Community-wide Screening in the Future Pandemic

Objectives In a dangerous future pandemic without effective vaccines and medicines, a reliable screening-and-isolation strategy can be the last opportunity to keep critical facilities and communities running and avoid a complete shutdown. Methods In this study, we introduced an epidemiological model that included essential parameters of infection transmission and screening. With varying parameters, we studied the dynamics of viral infection in the semi-isolated communities. Results In the scenario with a periodic infection screening once per 3 days and a viral basic reproduction number 3.0, more than 85% of the infection waves have a duration less than 7 days and the infection size in each of the waves is generally less than 4 individuals when the efficiency of infection discovery is 0.9 in the screening. When the period of screening was elongated to once per 7 days, the cases of infection dramatically increased to 5 folds of that mentioned previously. Further, with a weak discovery efficiency of 0.7 and the aforementioned low screening frequency, the spread of infection would be out of control. Conclusions Our study suggests that frequent periodic screening is capable of controlling a future epidemic in a semi-isolated community without vaccines and medicines. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by grants from National Natural Science Foundation of China (grant numbers 32170634, and 31871255 to Y.H). Y.H. was also supported by Shanghai Municipal Science and Technology (grant 2017SHZDZX01). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All codes and other material used in this study are publicly available upon request * SIR : Susceptible-Infectious-Recovered SEIR : Susceptible-Exposed-Infectious-Recovered COVID-19 : Coronavirus Disease 2019