Epidemiology

Author: Rino , Created on Apr 24, 2025 2 min read

The science that studies the distribution, determinants, and control of health-related states and events in populations, often considered the cornerstone of public health.

medicine public-health statistics

Epidemiology

What Does Epidemiology Do?

Epidemiology is the science that studies the distribution, determinants, and control of health-related states and events (including diseases) in specified populations. It is often considered the cornerstone of modern public health.

At its core, it seeks to answer three classic questions:

  • When and where does the disease occur, and who does it affect? (Distribution)
  • Why do these people get sick, but not others? (Determinants)
  • What can we do to prevent and control the disease? (Control)

Wisdom from History: From Plague to Pump

Many principles of modern epidemiology were learned the hard way while combating large-scale historical pandemics. For example, studying The Black Death led to the gradual understanding of the importance of concepts like Quarantine.

A landmark case occurred in mid-19th century London. During a devastating cholera outbreak, the prevailing view was that it was caused by "miasma" (bad air). But a physician named John Snow (British, 1813-1858) was skeptical. He marked cases on a map, and all clues eventually pointed to a single contaminated water pump on Broad Street. He had the pump handle removed, and the epidemic subsided. This story became a classic case of epidemiological fieldwork.

A Few Core Concepts

  • Incidence: Measures the rate of new cases occurring in a healthy population over a specific period.
  • Prevalence: Measures the proportion of a population that has a disease at a specific point in time (both new and old cases).
  • Mortality Rate: Measures the frequency of death from a disease within a population over a specific period.
  • Popular Science:
    • (Book) The Ghost Map: The Story of London's Most Terrifying Epidemic—and How It Changed Science, Cities, and the Modern World by Steven Johnson. (ISBN: 9781594482694)
  • Textbooks:
    • (Book) Epidemiology: An Introduction by Kenneth J. Rothman. (ISBN: 9780199754557)
  • Further Reading:
    • (Book) Modern Epidemiology by Rothman, Greenland, and Lash. (ISBN: 9781451190052)