  The behaviour of individuals is a main actor in the control of the spread of
a communicable disease and, in turn, the spread of an infectious disease can
trigger behavioural changes in a population. Here, we study the emergence of
the individuals protective behaviours in response to the spread of a disease by
considering two different social attitudes within the same population:
concerned and risky. Generally speaking, concerned individuals have a larger
risk aversion than risky individuals. To study the emergence of protective
behaviours, we couple, to the epidemic evolution of a
susceptible-infected-susceptible model, a decision game based on the perceived
risk of infection. Using this framework, we find the effect of the protection
strategy on the epidemic threshold for each of the two subpopulations
(concerned and risky), and study under which conditions risky individuals are
persuaded to protect themselves or, on the contrary, can take advantage of a
herd immunity by remaining healthy without protecting themselves, thanks to the
shield provided by concerned individuals.
