Formula (6) determines the critical probability (p*) of effectiveness of a food association
program above which the diet-problem-endemic state(s) disappear. Figure 7 shows the
critical level of the food association effectiveness p* as a function of the contact rate β. The
vertical line β = β- separates between nonexistence and existence of a backward bifurcation.
Therefore, for β ≤ β-, the curve p = p*2 separates between existence and nonexistence of
diet-problem-endemic equilibria. Thus, a probability of effectiveness slightly above p?
2 ensures an effective control of the diet-endemic problem. However, if _