Mathematical Modeling Analysis For Transmission Ability And Regional Differences Of COVID-19

The thesis mainly studies the transporting ability of COVID-19 in China to provide a mathematical basis for epidemic prevention and control.Here is the introduction for this thesis:The thesis,in Chapter 1,uses the datum of 425 early confirmed cases in Wuhan to estimate basic reproduction number and serial interval by MLE at the same time.The basic reproduction number of Wuhan’s COVID-19 is 2.42,and the average serial interval is 8.85 days.The estimated results fit well with the conclusions of epidemiological investigation.In order to quantify the transmission intensity of COVID-19 over time,based on the daily epidemic data,the instantaneous reproduction number of each region in February 2020 is estimated by the statistical model,so as to characterize the instantaneous transmission capacity of the disease.By the end of February 2020,COVID-19 in each region been controlled well.Due to the different prevention and control strategies adopted by all regions of China to prevent the large-scale spread of the epidemic,we define a new epidemic control efficiency formula based on the instantaneous reproduction number,and qualitatively evaluate the impact of the prevention and control strategies adopted by different regions.The results show that there are many imported cases at the present stage,and the risk of recurrence is still high in China.There are obvious regional differences in the control effect among different regions.In Chapter 2,we analyze the spread of COVID-19 in various regions of China.We use logistic model to describe the phenomenon of slow transmission speed in the process of infectious disease transmission.We also estimate the total invasive reproduction number by using exponential growth model for fitting the time series of various provinces and cities in China.According to the traits of epidemic situation in China,we calculate the population outflow before the closure of Wuhan by the big data of population flow.Through correlation analysis,the relationships between the reproduction number and the population density and the population outflow from Wuhan are explored.The results show a significant positive correlation between the reproduction numbers and the population input sizes from Wuhan,which indicates that the large-scale population movement contributed a lot to the geographic spread of COVID-19 in China.What’s more,there is significant correlation between reproduction number and population density,which indicates that the higher population density intensifies the spread of disease.In the early stage of infectious diseases,there are a considerable number of imported cases.Through the information of epidemiological investigation,we classify the imported cases and local cases in some cities,and quantify the local spread of the epidemic by net reproduction number.In addition,the Erlang distribution is used to eliminate the gap of infection,onset and diagnosis,and the daily number of patients onset and infected is obtained.The results are consistent with the real datum,which is reliable.