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arXiv 2006.01586q-bio.PEstat.ME
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传染病的随机建模,第一部分:了解负二项分布并更可靠地预测流行病

Stochastic Modeling of an Infectious Disease, Part I: Understand the Negative Binomial Distribution and Predict an Epidemic More Reliably

Hisashi Kobayashi

摘要:

为什么COVID-19的流行模式在人口、医疗基础设施和人们行为相似的不同城市或国家之间如此不同?为什么所谓的专家所作的关于感染或死亡人数的预测或预测往往是严重错误的?本研究的目的是为了更好地理解流行病的随机性,并回答上述问题。许多关于传染病的研究都是基于“SIR确定性模型”(Kermack and McKendrick:1927)。我们将探索随机模型,可以捕捉传染病看似不稳定的行为的本质。一个随机模型,在其制定,考虑到随机性质的传染病。本文所研究的随机模型是基于在研究某些生物种群的增长或灭绝时提出的“带移民的生灭过程”(简称BDI)。然而,流行病学界尚未对BDI过程模型进行调查。BDI过程是为数不多的生灭过程之一,我们可以用解析法求解。其时间相关概率分布函数是“负二项分布”,其参数$r$小于$1$。过程的“变异系数”大于$\sqrt{1/r} > 1$。此外,它有一个像zeta分布一样的长尾。这些特性解释了为什么感染模式表现出巨大的变化。确定性模型预测的感染人数远大于分布的中位数。这就解释了为什么任何基于确定性模型的预测往往会失败。

英文摘要:

Why are the epidemic patterns of COVID-19 so different among different cities or countries which are similar in their populations, medical infrastructures, and people's behavior? Why are forecasts or predictions made by so-called experts often grossly wrong, concerning the numbers of people who get infected or die? The purpose of this study is to better understand the stochastic nature of an epidemic disease, and answer the above questions. Much of the work on infectious diseases has been based on "SIR deterministic models," (Kermack and McKendrick:1927.) We will explore stochastic models that can capture the essence of the seemingly erratic behavior of an infectious disease. A stochastic model, in its formulation, takes into account the random nature of an infectious disease. The stochastic model we study here is based on the "birth-and-death process with immigration" (BDI for short), which was proposed in the study of population growth or extinction of some biological species. The BDI process model ,however, has not been investigated by the epidemiology community. The BDI process is one of a few birth-and-death processes, which we can solve analytically. Its time-dependent probability distribution function is a "negative binomial distribution" with its parameter $r$ less than $1$. The "coefficient of variation" of the process is larger than $\sqrt{1/r} > 1$. Furthermore, it has a long tail like the zeta distribution. These properties explain why infection patterns exhibit enormously large variations. The number of infected predicted by a deterministic model is much greater than the median of the distribution. This explains why any forecast based on a deterministic model will fail more often than not.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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