The Building Of Individual-based Infectious Disease Model And Applications

Infectious disease is a major threat to human health. Although the improvement of health conditions and advances in modern medicine have greatly enhanced the ability of human beings to deal with infectious diseases, the global outbreaks of emerging infectious diseases still shows a rising trend. High population aggregation and the increasing mobility make infectious diseases spread across regions very quickly, which bring great challenges to the prevention and control of infectious diseases.In the process of making prevention and control strategy for infectious diseases, the main approaches are PI(pharmaceutical interventions) such as immunization and drug treatment, and NPI(Non-Pharmaceutical Interventions) such as risk communication and school closure. In most cases, selection and application of these interventions is based on historical experience. But for large-scale pandemic of newly emerging infectious diseases, people usually know little about them and lack effective vaccine and drugs. So the use of NPI is particularly important, and the integrated application of NPI is a complex problem. These interventions will generate broad social and economic costs when controlling the spread of infectious diseases. The analyse of the use of these interventions will be helpful to better understand the effectiveness of these interventions with different length and timing. This gives people a reference on when these interventions should begin and how long these interventions should last. Individual-based infectious disease model(IBIDM) is an important scientific means to achieve this purpose.IBIDM models for individual units,and fully shows the heterogeneity of different unit. Compared with classical mathmatical models, IBIDM can simulate in a smaller size and is very flexible. So IBIDM can analyse multiple interventions in different sizes, which will be a scientific support for public health department to make policy in the prevention and control of infectious disease. Because of the increasingly rich of basic data and the development of high performance computing, infectious disease models in unit size become a hotspot in infectious disease modelling and the prevention and control policy analysis.This thesis aims at quantitative evaluation problems of NPI in the outbreak of infectious diseases, and constructs social contact networks for massive infectious disease spread and network transmission dynamics based on unit size modelling. It also assesses the intervention effectiveness of two NPIs:behaviour guidance and school closure with constructed computer models. There are three main research contents:(1) Method research of the construction of IBIDM. This thesis analyses the building process of IBIDM, research the method of reconstructing the virtual social contact network based on the theory of synthetic population modelling and its parallel computing algorithem of transmission dynamics.(2) The analysis of the effect of human behaviour on the dynamics of infectious diseases transmission. This paper studies the interaction relationship between human behaviour, crisis information and the dynamics of infectious diseases, constructs a human behaviour model based on information perception, and analyses the effect of human behaviour on the dynamic of infectious diseases.(3) The assessment of the effect of school closure on pandemics of an emerging influenza. Assess the effect of different choices of the timing and length of school closure on epidemics.The main results and innovation points are as follows:(1) The construction of an individual-based infectious disease model. This thesis analyses the theory of the construction of IBIDM and its transmission dynamics, presents the building process of IBIDM, the generating method of social contact network and the parallel computing algorithm of IBIDM. The synthetic society includes synthetic population, virtual family, virtual school and virtual workplace. Social contact network includes family contact network, school contact network, work contact network, friends contact network, community contact network and commuter contact network. The realization part includes the partition of population data and the parallel computing architecture of the model. We constructed an IBIDM of Beijing which provides the computing environment for the assessment of human behaviour change and school closure.(2) The analysis of the effect of human behaviour change on epidemic dynamics. This thesis models the interaction relationship between human behaviour, crisis information and the transmission behaviour of infectious diseases, constructs a human behaviour model of information perception based on global crisis information and local crisis information. We simulated the effect of human behaviour change on the transmission behaviour of infectious diseases with Beijing’s IBIDM. The effect of different degrees of human behaviour on the behaviour of infectious diseases transmission is assessed. The result shows that human behaviour change can effectively lower the peak value and attack rate of infectious diseases, and sensitivity analysis shows that the more sensitive human behaviour is to crisis information,the better human behaviour perform in disease control. Sensetivity analysis of the length of perception interval shows that the shorter the perception interval is, the better human behaviour perform in disease control. The research has practical value in making strategies of crisis communication in infectious diseases pandemics.(3) Assessment of the effect of school closure on influenza pendemics. School closure is an important NPI in an influenza pendemic. This thesis assesses the efficiency of school closure with different timing and length in an influenza pandemic by IBIDM. The result shows that school closure in interpandemic phase and decline phrase has little effect on controlling the pandemic, school closure in pandemic phase can reduce the peak infected and attack rate effectively,and it also delays the peak infected time. School closure in peak phrase can reduce the peak infected and attack rate effectively, but doesn’t delay the peak infected time. Besides, the effect of school closure in interpandemic phrase and decline phrase is insensitive to the length of school closure, while the effect in pandemic phrase and peak phrase is sensitive to the length of school closure, increasing the length of school closure will markedly enhance the efficiency of school closure. This research has reference value for the choice of the timing and length of school closure.This thesis constructs an IBIDM specific to droplet transmission and direct transmission infectious disease based on social contact networks, analyses the effect of human behaviour on infectious disease transmission behaviour, assesses the effect of school closure on influenza pandemics. The constructed model has scientific significance to improve the decision-making of infectious disease prevention and control. The assessment has practical significance to the choice of school closure and crisis communication in infectious disease emergency.