The cultural fitness of self-medicative treatments

, (left and middle), and probability of spread of treatments (right) plotted as a function of treatment efficacy,

. Left (a): cultural fitness

; we set

so that

. Middle (b): cultural fitness

; when treatment is prophylactic (

). Right (c): The ultimate probability of spread (rugged lines) and the probability of spread from an innovator (smooth lines) for various rates of relapse

(indicated by colour). Unless stated otherwise, parameter values are

,

,

,

,

,

,

and

(see Methods for interpretation of parameter values).