Study On The Transmission Dynamics Of Novel Coronavirus Pneumonia In A Relatively Closed Environmen

The Novel coronavirus pneumonia(Corona Virus Disease 2019,COVID-19),known as "Virus pneumonia",is an acute respiratory infection caused by a novel coronavirus(SARS-Co V-2)with a risk of death.Since the outbreak of COVID-19 at the end of 2019,it has caused tremendous damage worldwide.Through the joint efforts of the whole country,the current situation of COVID-19 in China is relatively stable.However,with the global epidemic of COVID-19 entering its fourth wave and the emergence of mutant strains that are more transmissible and insidious,the epidemic has recurred in China.Under the dual pressure of imported and local cases,the epidemic situation in China has changed from a multi-location outbreak to a highly localized and multi-point epidemic situation,especially in some relatively closed environments where sudden outbreaks and aggregated outbreaks occur frequently.The relatively closed environment is more conducive to virus transmission,and the stronger transmission and invisibility of the new mutant strains increase the risk of virus transmission in the relatively closed environment,adding new difficulties to the epidemic prevention.Therefore,more targeted research is needed to determine appropriate control measures to prevent the spread of the outbreak on a larger scale.This thesis uses the Diamond Princess outbreak and the Ningbo bus outbreak as examples to model and analyze the transmission dynamics of COVID-19 within a relatively closed environment with two types of heterogeneous groups and within a relatively closed environment with high aggregation.In this thesis,an agent-based model was used to model each of these two cases,and the parameter groups were selected using the Latin hypercube sampling method,and the final parameter groups were determined by comparing the residual sum of squares and variances of the results of the parameter group runs with the actual number of infections and the results of hypothesis testing.The model simulation was used to investigate the influence of the interaction behavior of two heterogeneous groups in a relatively closed environment on the transmission dynamics of the epidemic,as well as the influence of the aerosol transmission route and the contaminant transmission route on the final number of infections during the aggregated transmission process,and to formulate a series of control measures accordingly and evaluate the prevention and control effectiveness of the corresponding control measures.The simulation results of the Diamond Princess case showed that most of the infected passengers on the cruise ship were infected by other passengers,but during the first days of the quarantine,the number of passengers infected by staff was much higher than the number of passengers infected by passengers.This suggests that due to the nature of the staff’s work,they played a key role in the spread of the outbreak during the initial days of quarantine.If staff testing efforts were strengthened early and infected staff were removed from the ship in time,the eventual number of infections would be greatly reduced.The effectiveness of these routine control measures,including increased frequency of hand washing and contaminant cleanup,would be enhanced if this control measure of increased staff testing were supplemented with other routine control measures.The simulation results of the Ningbo bus case showed that the aerosol route was the main mode of virus transmission in the aggregate transmission,and 2/3 of the infected people were eventually infected through the aerosol transmission route.In this case,if passengers wear masks,reduce the frequency of exposure to contaminants and increase the frequency of hand washing to reduce the transmission rate,the final number of infections can be largely reduced.