Keeping the kids at home can limit the persistence of contagious pathogens in social animals

Lucile Marescot; Mathias Franz; Sarah Benhaiem; Heribert Hofer; Marion East; Stephanie Kramer-Schadt

used an individual-based model to investigate for the first time this second 96 mechanism and test the prediction that the probability of epidemic fade-out increases in 97 populations (i.e. networks) of social species with an ORC trait. For this purpose, we 98 developed an SIR model to describe pathogen transmission and host population dynamics. In 99 order to assess how consistently the probability of epidemic fade-out increased due to ORC, 100 we systematically varied parameters likely to influence pathogen transmission dynamics: (1) 101 host birth rate, (2) host death rate (which occurs independently of infection), (3) contact rates 102 between members of different groups, (4) infection rate at contact, (5) individual infection 103 length, (6) virulence (i.e. the increase in host death rate due to infection), and (7) whether 104 transmission is frequency or density-dependent. For each specific combination of parameters, 105 we investigated two scenarios. First, we set up a baseline scenario in which rates of between-106 group contact were identical for individuals of all ages. Second, we investigated an ORC 107 scenario in which individuals below a given age-threshold could not contact members of 108 other groups, i.e. their rates of between-group contact were set to zero. This is simulating the 109 legal requirements of confinement put into action by authorities to limit the spread of 110 pandemics, e.g. during the COVID-19 pandemic; the closure of schools and prevention of 111 contact between young and elderly people, including within households (e.g. Anderson et al. 112 2020, Kelvin and Halperin 2020). Because ORC decreases R0, we adjusted the infection rate 113 in the baseline scenario such that the value of R0 was always identical in both scenarios to 114 insure that the emergence of a more efficient immunity barrier are directly related to the ORC 115 trait, and not to its mediated effect on R0. We discuss our results in relation to behavioural mechanisms yielding herd immunity as well as the likely outcomes of altering social network 117 modularity through management measures.