Epidemiologists collect and analyze data to investigate health issues. For example, an epidemiologist might collect and analyze demographic data to determine who is at the highest risk for a particular disease. Research epidemiologists typically work for universities. Applied epidemiologists work with governments, addressing health crises directly. The most common problem both types of epidemiologists work on is infectious diseases, but they examine other public health issues, as well. Epidemiologists who work in private industry commonly work for health insurance companies or pharmaceutical companies. Those in non-profit companies often do public advocacy work. Becoming an epidemiologist often requires a master's degree in public health. If this field interests you, take as many courses in biological sciences as you can.