Departamento de Física, Instituto de Física Aplicada, Universidad Nacional de San Luis-CONICET, San Luis, Argentina.
PLoS One. 2011;6(7):e21946. doi: 10.1371/journal.pone.0021946. Epub 2011 Jul 8.
Some epidemics have been empirically observed to exhibit outbreaks of all possible sizes, i.e., to be scale-free or scale-invariant. Different explanations for this finding have been put forward; among them there is a model for "accidental pathogens" which leads to power-law distributed outbreaks without apparent need of parameter fine tuning. This model has been claimed to be related to self-organized criticality, and its critical properties have been conjectured to be related to directed percolation. Instead, we show that this is a (quasi) neutral model, analogous to those used in Population Genetics and Ecology, with the same critical behavior as the voter-model, i.e. the theory of accidental pathogens is a (quasi)-neutral theory. This analogy allows us to explain all the system phenomenology, including generic scale invariance and the associated scaling exponents, in a parsimonious and simple way.
有些流行病被经验观察到表现出所有可能规模的爆发，即无标度或标度不变。对于这一发现提出了不同的解释；其中有一种“偶然病原体”模型，它导致幂律分布的爆发，而不需要明显的参数微调。有人声称这个模型与自组织临界性有关，其临界性质被推测与定向渗流有关。相反，我们表明这是一个（准）中性模型，类似于在人口遗传学和生态学中使用的模型，具有与投票模型相同的临界行为，即偶然病原体理论是一个（准）中性理论。这种类比使我们能够以简洁和简单的方式解释所有的系统现象，包括通用的标度不变性和相关的标度指数。
