Study on the epidemic trend of Omicron in Shanghai based on the reproduction number
Objective To study the epidemic trend of Omicron in Shanghai as of May 9,2022 by estimating the early reproduction number(R)before closed management and the subsequent changes of effective reproduction number(Rt).Methods Exponential growth method,maximum likelihood method and next generation matrix method were used to estimate R,and Bayesian method,Time-Dependent and New Time-Varying were used to estimate Rt.Results As of March 29,2022,the growth of Omicron epidemic in Shanghai followed the exponential growth.The early reproduction number R estimated by three methods was 2.36(95％CI:2.33-2.38),2.14(95％CI:2.11-2.18)and 2.29(95％CI:2.22-2.38),respectively.Conclusions As the values of R were relatively large,the early epidemic situation in Shanghai was severe.The turning point of the epidemic was on April 7,and the implementation of sealing and control management measures had effectively slowed down the increment of the epidemic cases.Among the methods for calculating the Rt,the Time-Dependent and New Time-Varying can quickly respond to the dynamic trend of the epidemic,while the Bayesian method was relatively slow.Besides,when the reported data fluctuated greatly,the denominator would be zero,thus R,would be unable to calculate.
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