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目的运用时滞离散SEIR模型预测水痘暴发疫情发病数,以评估疫情控制措施的实际应用效果。方法采用时滞离散SEIR模型对暴发疫情数据进行模拟,评价病例隔离、应急接种等疫情控制措施的实施效果。结果不采取任何干预措施时,模拟水痘暴发疫情理论的发病数为434人,罹患率为30.58%(434/1 419),流行过程历时3个月,发病高峰在首发病例发生后60天,流行过程中可见明显的“代际”现象,每代间隔2周左右。模拟在首发病例发病当日、第14、28、42天开始实施100%病例隔离,总发病数分别为5、13、34和78人。模拟在首发病例发病后第14天采取病例隔离措施,隔离率分别为30%、50%、70%和90%时,总发病数分别为370、323、230和52人。模拟首发病例发病当日、第14、28和42天时实施应急接种,接种率100%时,总发病数分别为5、14、37和84人。模拟首发病例发病后第14天实施应急接种,接种率分别为30%、50%、70%和90%时,总发病数分别为262、150、52和19人。本文模拟的水痘暴发疫情实际发病118人,隔离率为82.20%(97/118),模拟首发病例发病后第30天采取病例隔离措施,隔离率82.20%,理论总发病数为148人,比实际发病多30人。结论时滞离散SEIR模型能较好地预测水痘暴发疫情规模,可从理论上评价防控措施对疫情的影响;尽早严格实施病例隔离和高覆盖率的应急接种均是有效的水痘疫情控制措施。
Objective To predict the actual number of outbreaks of varicella outbreaks using time-varying discrete SEIR model in order to evaluate the practical effect of epidemic control measures. Methods Discrete SEIR model was used to simulate outbreak data to evaluate the effect of isolation and emergency vaccination. Results Without any intervention, the incidence of simulated episode of chickenpox was 434 with an attack rate of 30.58% (434/1 419). The epidemic lasted for 3 months. The peak incidence peak was 60 days after the first case occurred Obvious “generation ” phenomenon can be seen in the process, each generation is about 2 weeks apart. On the day of onset of the first case, 100% of the cases were isolated on the 14th, 28th and 42nd days. The total number of cases was 5, 13, 34 and 78 respectively. Simulations were performed on the 14th day after the onset of the first case and the isolation rates were 30%, 50%, 70% and 90% respectively. The total incidence was 370, 323, 230 and 52 respectively. On the day of the onset of onset of the first episode, emergency vaccination was carried out on the 14th, 28th and 42nd days. The total incidence was 5,14,37 and 84, respectively, when the vaccination rate was 100%. The number of onset cases was 262, 150, 52 and 19, respectively, when emergency vaccination was performed on the 14th day after onset of the onset of illness. The vaccination rates were 30%, 50%, 70% and 90% respectively. In this paper, the actual incidence of chickenpox outbreak was 118 and the isolation rate was 82.20% (97/118). Case isolation was taken on the 30th day after the first onset of the disease. The isolation rate was 82.20% and the total theoretical incidence was 148, The incidence of more than 30 people. Conclusion The discrete-time SEIR model can predict the scale of outbreak of chicken pox and evaluate the effect of prevention and control measures on epidemic situation. It is an effective measure to control the epidemic of chicken pox as soon as possible with strict isolation and high coverage emergency vaccination.