The principal constructs of the helath belief model are perceived susceptibility, perceived severity, perceived benefits, cues to action, and self efficacy. Perceived susceptibility refers to a person's belief that constracting the disease may result in harsh health consequences. Taken together, these two constructs form the perceived threat to health. The perceived benefits involve the beliefs of individuals in the value of adhering to health related measures to prevent or reduce the illness or disease, whereas perceived barriers refer to the belief in the costs that limit a person to carry out the necessary health related measures. There needs to be greater perceivd benefits than perceived costs in order for a person to carry out the proposed health related measures to lesson the disease impact