What field of study investigates the frequency and distribution of diseases?

The correct choice pertains to the field of study known as epidemiology, which specifically focuses on the analysis of the distribution and determinants of health and disease conditions in defined populations. Epidemiologists investigate how often diseases occur in different groups of people and why, as well as the factors contributing to those occurrences.

This discipline is crucial for public health because it helps identify risk factors for health outcomes and leads to the development of strategies for prevention and control of diseases. By employing statistical methods and researching patterns in disease occurrence, epidemiologists provide valuable insights that inform health policies and practices.

Pathology, while related, is primarily concerned with the study of the nature and causes of diseases and the changes that occur in the tissues and organs. Virology focuses specifically on viruses and viral diseases, while microbiology encompasses a broader range of microorganisms, including bacteria, fungi, and parasites. However, these fields do not primarily deal with the frequency and distribution of diseases as epidemiology does.