Quasi-Neutral Theory of Epidemic Outbreaks

PINTO O. A; MUÑOZ M.A.

PLOS ONE

PUBLIC LIBRARY SCIENCE

Año: 2011 vol. 6 p. 1 - 7

1932-6203

Some epidemics have been empirically observed to exhibit outbreaks of all possible sizes, i.e., to be scale-free or scaleinvariant.Different explanations for this finding have been put forward; among them there is a model for ‘‘accidentalpathogens’’ which leads to power-law distributed outbreaks without apparent need of parameter fine tuning. This modelhas been claimed to be related to self-organized criticality, and its critical properties have been conjectured to be related todirected percolation. Instead, we show that this is a (quasi) neutral model, analogous to those used in Population Geneticsand Ecology, with the same critical behavior as the voter-model, i.e. the theory of accidental pathogens is a (quasi)-neutraltheory. This analogy allows us to explain all the system phenomenology, including generic scale invariance and theassociated scaling exponents, in a parsimonious and simple way.