Compartment Model Based On Maximum Likelihood Estimation To Research COVID-19

In the face of the massive spread of COVID-19 in various regions,the Chinese government is actively taking preventive and control measures.Considering the great risk of increased infectiousness of virus mutations and the fact that economic activities are recovering,the spread and severity of COVID-19 needs to be monitored in real time.Therefore,the causes and patterns of the epidemic are summarised by studying the spread of the disease and the main factors affecting it.Thesis first examines the spread of the epidemic in the community by addressing the fact that the new crown epidemic has an incubation period and the presence of a large number of asymptomatic individuals.The effectiveness of vaccination and isolation measures in controlling the spread of the epidemic was then further investigated.The details of the study were as follows:Firstly,the Becker chain binomial model was used to elucidate the pattern of transmission of the epidemic in households and to find the chain of infection and probability for different household size.Secondly,the probability distribution of the final number of infections in the household population is derived.Next,the chain binomial model is combined with the maximum likelihood estimation method to find the probability of escape from infection for different types of households separately and to obtain an estimate of the transmission coefficient.Then,in order to study the spread of the current epidemic in the community,the SEAIR model was developed for the incubation period and asymptomatic transmission of the new crown epidemic,and the basic regeneration number expression was derived using the next generation matrix method.In the absence of any effective measures,an outbreak will occur in the community.Finally,numerical simulations were carried out using the Eulerian approximation to determine the effect of the infectiousness reduction factor for asymptomatic patients,the proportion of asymptomatic infected persons and the length of the incubation period on the basic regeneration number.Next,vaccination and isolation measures are applied to control the new crown pandemic.In order to simulate the spread of neo-crown,the SVEAI_QI_NR epidemiological dynamics model with control measures was developed based on the SEIAR model.On this basis,the control regeneration number is calculated and the cost expressions for the adoption of control measures are derived.Finally,the effectiveness of the two control measures was evaluated by means of numerical simulation analysis.It is concluded from thesis that it is important to take strict control measures to isolate as many infected people as possible in the early stages of an outbreak,and to accelerate the vaccination programme while investing in research and development to ensure vaccine effectiveness.