ABSTRACT
Recall the definition of epidemiology-the study of the occurrence and distribution, cause and control, treatment and prevention of disease and other morbid conditions. In explaining the occurrence of disease and other morbid conditions, epidemiologists rely on the principle known as the epidemiological triad. Within this triad is the necessary factor or agent as well as the sufficiency factors of host and environment. Although the triad is useful in explaining disease occurrence, it is limited in explaining disease distribution.
