Final answer:
Epidemiologists study the occurrence, distribution, and determinants of health and disease in a population. They collect data to track the spread of diseases and develop strategies to prevent their incidence.
Step-by-step explanation:
An epidemiologist studies the occurrence, distribution, and determinants of health and disease in a population. They collect data about a particular disease and track its spread to identify the original mode of transmission. Epidemiologists work with historians to understand the way a disease evolved over time and gather information from clinical records, patient interviews, and other means. Their findings are used to develop strategies and public health policies to reduce the incidence of diseases.