According to Stanhope and Lancaster (2010) the web of causation “…recognizes the complex interrelationships of many factors interacting, sometimes in subtle ways, to increase (or decrease) the risk of disease” (p. 163). All things that can affect risk of disease are divided into one of three categories, agents, host, or environment. Examples of agents include infectious agents such as bacteria and viruses, chemical agents such as heavy metals and pesticides, or physical agents such as heat, cold, or radiation. Host factors include genetic susceptibility, physical characteristics such as age, sex, or immunization status and lifestyle habits such as being a smoker, or being inactive versus active. Finally environment includes climate, human population distribution, socioeconomic factors, and working conditions.…