Mathematically modeling spillovers of an emerging infectious zoonosis with an intermediate host.

Katherine Royce,Feng Fu,Chris T Bauch

doi:10.1371/journal.pone.0237780

Abstract

Modeling the behavior of zoonotic pandemic threats is a key component of their control. Many emerging zoonoses, such as SARS, Nipah, and Hendra, mutated from their wild type while circulating in an intermediate host population, usually a domestic species, to become more transmissible among humans, and this transmission route will only become more likely as agriculture and trade intensifies around the world. Passage through an intermediate host enables many otherwise rare diseases to become better adapted to humans, and so understanding this process with accurate mathematical models is necessary to prevent epidemics of emerging zoonoses, guide policy interventions in public health, and predict the behavior of an epidemic. In this paper, we account for a zoonotic disease mutating in an intermediate host by introducing a new mathematical model for disease transmission among three species. We present a model of these disease dynamics, including the equilibria of the system and the basic reproductive number of the pathogen, finding that in the presence of biologically realistic interspecies transmission parameters, a zoonotic disease with the capacity to mutate in an intermediate host population can establish itself in humans even if its R0 in humans is less than 1. This result and model can be used to predict the behavior of any zoonosis with an intermediate host and assist efforts to protect public health.

Highlights

Zoonotic diseases, which originate in animals and infect humans, are one of the most concerning epidemic threats of the 21st century and form 60% of all known infectious diseases [1]
While the variety and inconsistency of these sources reflects the need for more data and research into the actual effects of particular zoonoses [35,36,37,38]), and it is crucial for public health interventions based on a mathematical model to know the accuracy of each parameter, their specific values are relatively unimportant for the theoretical results presented here, as the analysis of the system holds for all parameter values
This concerning result for public health offers areas in which policy rather than medical interventions can be more effective in controlling disease. We establish that this model of the entire path of an emerging infectious zoonosis has one unique disease-free equilibrium and one endemic equilibrium, and that the stability of these points depends on pd, ph, and μ, the contact probabilities between species and the pathogen’s rate of mutation

Summary

Introduction

Zoonotic diseases, which originate in animals and infect humans, are one of the most concerning epidemic threats of the 21st century and form 60% of all known infectious diseases [1]. Zoonoses such as HIV-AIDS, avian influenza, SARS, Ebola, Nipah, Hendra, and rabies all trace their origin to nonhuman reservoir species [2], and zoonoses comprise 75% of emerging infectious disease [3]. The World Health Organization cites “Disease X”, a pathogen currently unknown to cause human disease that might evolve to become more transmissible among humans, as a priority for research and development in pandemic prevention [4], a threat underscored in recent months by the SARS-CoV2 pandemic.

Methods

Results

Discussion

Conclusion