The Influence Of Social Behavior On Competition Between Virulent Pathogen Strains

Abstract

6Infectious disease interventions like contact precautions and vaccination have proven effective in disease 7 control and elimination. The priority given to interventions can depend strongly on how virulent the pathogen 8 is, and interventions may also depend partly for their success on social processes that respond adaptively 9 to disease dynamics. However, mathematical models of competition between pathogen strains with differing 10 natural history profiles typically assume that human behaviour is fixed. Here, our objective is to model the 11 influence of social behaviour on the competition between pathogen strains with differing virulence. We couple 12 a compartmental Susceptible-Infectious-Recovered model for a resident pathogen strain and a mutant strain 13 with higher virulence, with a differential equation of a population where individuals learn to adopt protective 14 behaviour from others according to the prevalence of infection of the two strains and the perceived severity of 15 the respective strains in the population. We perform invasion analysis, time series analysis and phase plane 16 analysis to show that perceived severities of pathogen strains and the efficacy of infection control against 17 them can greatly impact the invasion of more virulent strain. We demonstrate that adaptive social behaviour 18 enables invasion of the mutant strain under plausible epidemiological scenarios, even when the mutant strain 19 has a lower basic reproductive number than the resident strain. Surprisingly, in some situations, increasing 20 the perceived severity of the resident strain can facilitate invasion of the more virulent mutant strain. Our 21 results demonstrate that for certain applications, it may be necessary to include adaptive social behaviour 22 in models of the emergence of virulent pathogens, so that the models can better assist public health efforts 23 to control infectious diseases. 24 1 . CC-BY-NC-ND 4.0 International license is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. It . https://doi.org/10.1101/293936 doi: bioRxiv preprint 25 Modern approaches to developing a theory of the spread of infectious diseases can be traced to 1927 when 26 Kermack and McKendrick developed an integro-differential equation model now widely described as the SIR 27 (Susceptible-Infected-Recovered) model [1]. The model tracks changes in the number of individuals suscep-28 tible to an infection S(t), the number of infected individuals I(t), and (implicitly) the number of recovered 29 individuals R(t). Compartmental models such as the SIR model are useful for mechanistic modelling of 30 infection transmission in populations. They have since been further developed to study the evolution and 31 epidemiology of multiple species of pathogens in a population or different strains of the same species [2]. 32Some models focus on between-host competition while some others on within-host competition [3]. Bull 33 suggested in the 1990s that coupling inter-host and i...

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