| ObjectiveTo analyze the dynamic changes of three local COVID-19 epidemics in Zhengzhou from 2020 to 2022,explore prevention and control strategies that are more applicable to the current epidemic situation and provide a scientific basis for effective prevention and control of local COVID-19 outbreaks in the future.MethodsCOVID-19 cases data were collected from the Health Commission of Henan Province,and the demographic,temporal and regional distribution characteristics of the three COVID-19 epidemics in Zhengzhou was analyzed by descriptive epidemiological methods.The transmission dynamics model of COVID-19 was established based on SEIR model to explore the dynamic changes of the epidemic transmission in Zhengzhou.Taking the third COVID-19 epidemic in Zhengzhou as an example,the effects of different prevention and control strategies were simulated.Results1.Epidemiological characteristics of COVID-19 in Zhengzhou: Demographic distribution: The sex ratios of male and female cases in the three epidemics were 1.12:1,1.11:1 and 0.63:1,respectively,and the age of cases was concentrated in the range from20 to 59.The first epidemic was mainly imported cases,while the second and third epidemics were mainly local cases.Temporal distribution: The first epidemic had a slower trend of increasing cases and a longer duration(31 days).Cases of the second and third epidemics were mostly detected in early stage of the outbreak,and a shorter duration(15 and 17 days).Regional distribution: Cases of the three COVID-19 epidemics in Zhengzhou were mainly distributed in Erqi District(197 cases,47.4%),followed by Jinshui District(54 cases,13.0%),Zhongyuan District(42 cases,10.1%)and Guancheng District(32 cases,7.7%).2.COVID-19 transmission dynamics in Zhengzhou: The first COVID-19 epidemic in Zhengzhou was spread of SARS-Co V-2 wild type,while the second and third epidemics were spread of Delta variant.The mutation of SARS-Co V-2 shortens the non-infectious incubation period,prolongs the recovery period of cases,reduces the vaccine protection rate and speeds up transmission of the epidemic.But the government strategies for preventing and controlling COVID-19 epidemic are also being refined,with the implementation of vaccination,large-scale nucleic acid testing,technology of big data tracking cases and other measures to achieve rapid prevention and control for epidemic.According to the variant of SARS-Co V-2 and progress of prevention and control strategies in Zhengzhou,the study adjusted corresponding parameters of the model and accurately simulated the transmission dynamics of the three epidemics in Zhengzhou.The Mean Absolute Percentage Error(MAPE)of fitted value and true value were 15%,5%,and 4%,respectively.3.Sensitivity analysis results: Sensitivity analysis showed that the cumulative number of cases and peak of isolated cases will decrease with the effective infectious period of cases shortens,transmission rates decline and vaccine effectiveness improves,and the duration of epidemics will be correspondingly shortened.Shortening the recovery period of cases will not affect the cumulative number of cases,but will reduce the peak of existing isolated cases.4.Simulation effects of different prevention and control strategies: The third epidemic in Zhengzhou was used as the baseline.If all prevention and control measures are relaxed,the cumulative number of cases and the peak number of existing isolated cases will be 18.5 times(2658 vs.143 cases)and 17.7 times(1642 vs.93 cases)of the baseline,respectively.If only prevention and control one of the effective infectious periods,infection rate and vaccine protection rate,the cumulative number of cases was at least 1.6 times higher than the baseline(227 cases vs.143 cases).If only two strategies were prevented and controlled,the best effect is a combination of strict strategies to reduce transmission rate and improve vaccine protection rate,which could result in a 33.5% reduction in cumulative cases(95 vs.143).If the effective infectious periods,transmission rate and vaccine protection rate were controlled simultaneously,the cumulative number of cases could be reduced by up to 51% from baseline(70 cases vs.143 cases).Conclusions1.The age of cases in the three COVID-19 epidemics in Zhengzhou was concentrated in the range from 20 to 59 and the outbreak occurred mainly in the Erqi District which has large population mobility and gathering.In the future,it is necessary to strengthen the prevention of key groups in these high-risk areas.2.The three COVID-19 epidemics in Zhengzhou were caused by different strains.The variant of SARS-Co V-2 is faster transmission and more infectious than the original strain,and also reduces the protective effectiveness of the vaccine,which is more likely to cause community transmission.Therefore,more targeted prevention and control strategies need to be developed according to characteristics of the variant.3.Shortening the effective infectious period,reducing the transmission rate and improving the effectiveness of vaccine are key strategies for the current epidemic prevention and control,which can be achieved through early screening of cases,precise prevention and control,and enhanced vaccination of vaccines.In addition,attention should be paid to the simultaneous implementation of these strategies. |
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