Final answer:
Epidemiology is the study of health and disease in a population, and it focuses on the frequency and distribution of diseases within human populations and environments. An epidemiologist collects data to track the spread of diseases and identify how they are transmitted.
Step-by-step explanation:
Epidemiology is the study of occurrence, distribution, and determinants of health and disease in a population. It is a part of public health and focuses on the frequency and distribution of diseases within human populations and environments. An epidemiologist collects data about a particular disease and tracks its spread to identify the original mode of the transmission.