The Effects Of Disease Control Measures On The Reproduction Number Of COVID-19

Reproduction number is an important parameter for epidemic analysis.This paper from reported cases,estimate the change of the reproduction number with time,due to COVID-19 disease control measures varying transmission rate.In a randomly mixed population,we consider a discrete time random SEIR model,according to the daily reported cases,we can calculate the number of incidences and infectious patients per day,and combine the distribution of infection period and latent period,we can obtain the estimation model of the number of reproduction over time.In order to further estimate the uncertainty of the reproduction number,we obtained the samples of daily incidences and infectious patients by Markov Chain Monte Carlo method.Combined with the real-time estimation model of the reproduction number established by us,the 95%confidence interval of the reproduction number is obtained.In order to verify that the model can reflect the effect of control measures on reproduction number,we use the simulated prevalence curve to verify.we set two different transmission rates,namely the cosine function and the step function,to simulate the influence of seasons and artificial control measures on the spread of infectious diseases.The simulation comparison shows that our method can effectively estimate the sudden and gradual changes in the reproduction number.We use the point estimation to get the distribution of the infectious period in British Columbia,Canada in 2020,and apply the reproduction number estimation model to the province,we get the change curve and confidence interval of the real-time reproduction number in the province.The results showed that the strengthening of control measures,such as enforce social distancing、limit congregations and close schools,had a significant impact on the number of reproduction,while the relaxation of enterprises’ reopening in May and schools’ reopening in September had significantly increased the reproduction number from 1 to around 1.7 at its peak value.Our method can be applied to other infectious diseases,such as pandemic and seasonal influenza.