Public Health is a vast interdisciplinary field of study that incorporates all the perspectives, roles, policies, and institutions required to keep our populations safe from illness and injury. Unlike the medical field, which focuses on the health of individuals, public health focuses on the health of communities and populations at local, national, and global levels. The study of public health covers a broad range of topics from the safety of food, water, and highways to examining how individual behaviors and the social environment contribute to the prevention of chronic health conditions such as heart disease, diabetes, and cancer. Knowledge of public health is an asset to all undergraduate students who, as world citizens, must cooperate in the effort to manage multiple, simultaneous threats to public health including: infectious diseases such as flu and SARS; chronic disease risk factors such as obesity and smoking; the unequal distribution of disease and risk factors in the population; and shifts in environmental risk factors resulting from climate change. All of these issues entail complex ethical questions about individual freedom, social responsibility, and human rights.