As an entry-level epidemiologist, your responsibilities include conducting research into the spread of disease, treatment of epidemics, and how to prevent epidemics and public health crises. You work under the supervision of a more experienced epidemiologist or a principal investigator who heads a research lab. Your duties depend on whether your office focuses on crafting public policy or conducting research, and they may include planning and conducting studies, collecting data for analysis, writing reports, or developing policy based on research.