Nutritional deficiencies are included under agent factors. Although too much of an agent can cause disease (such as obesity related to diabetes), so can too little of an agent. Relative risk indicates the extent
of excess risk incurred by exposure relative to nonexposure. Host factors are intrinsic factors and describe
one's susceptibility or response influence to the exposure to the agent, such as genetics, age, sex,
ethnicity, and human behavior. Environment factors are extrinsic factors and they influence the existence of the agent, exposure, or susceptibility to the agent such as physical environment, biological environment, and socioeconomic environment.