By Dr. Jay K. Varma
Physician, Epidemiologist, and Public Health Expert
Welcome to “Detecting and Responding to Infectious Disease Outbreaks,” a practical introduction to how public health professionals track, investigate, and control the spread of infectious diseases.
This material is adapted from lectures delivered to medical, graduate, and public health students, and designed to help learners—from novices to practitioners—understand the core frameworks that guide outbreak response.
Whether you’re a clinician, policymaker, journalist, or curious citizen, this guide offers insights into how public health problems are detected and how decisions made about how to control them.
By the end of this module, you should be able to:
Describe how infectious diseases are monitored in populations
→ Understand public health surveillance systems, their strengths, and their limitations.
Explain how to determine whether an increase in disease is a concern
→ Define key terms like outbreak, epidemic, and pandemic, and learn how thresholds are assessed.
Outline the steps used to investigate an infectious disease outbreak
→ Learn how epidemiologists identify cases, develop hypotheses, and determine sources.
Describe how public health officials select appropriate interventions
→ Explore the criteria for deciding whether a public health response is evidence-based, feasible, and equitable.
Apply a structured public health approach to outbreak detection and response
→ Learn how the cycle of surveillance, investigation, and intervention works in practice.
Each page in this module corresponds to a key component of the public health response process. We recommend following the pages in order, but each one also functions as a standalone explainer.
Use the top navigation to explore topics. Embedded links will take you to related glossary terms, YouTube videos, and external resources.
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Want additional background on surveillance, outbreaks, and interventions?
➡️ Visit the Resources & Downloads page for links to articles, guides, and other helpful information.
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Dr. Jay K. Varma is a physician, epidemiologist, and public health expert with more than 20 years of experience investigating and managing outbreaks around the world. He has led epidemic responses for the CDC, advised mayors and heads of state, and continues to educate the public through writing, media, and his YouTube channel Thermometer. Dr. Varma specializes in outbreak investigation, disease surveillance, evidence-based health interventions, and scientific communication.Â