Public health is the study of the overall health of a certain population of people, and why things such as pandemics or epidemics spread, and how to prevent them. Studies of the water supply is another aspect, since water is distributed to the public and can affect the health and wellbeing of citizens. The basic principle of public health is to focus on the prevention of disease versus the cure. It's important to prevent large scale diseases from spreading to begin with, as this can have real disastrous affects. For students looking into a career in public health, some examples are organizations such as the Centers for Disease Control and Prevention in Atlanta, or The Red Cross. A prime example of someone who has studied public health and all of its many aspects would be the Surgeon General of the United States. In positions such as this, education of the public is paramount, so a vast knowledge of how to educate people on taking care of themselves is the main focus.