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Patient Zero

The Origins, Risks, and Prevention of Emerging Diseases

Andrew E. Lyman-Buttler

Thomas Edison High School


Emerging diseases and potential pandemics make the news nearly every year. Students (and everyone else) may wonder where new infectious diseases come from, how scientists assess the risk of a pandemic, and how we might go about preventing one. This case study uses a PowerPoint presentation to explore these questions by focusing on HIV, a pandemic that began as an emerging disease. The storyline progresses backwards through time as scientists attempt to unravel the origins of a new, mysterious plague. Much of the case relies on audio excerpts from an episode produced by Radiolab, an acclaimed radio show that explores a variety of topics in science and culture (www. Students use graphics, animations, and sound clips presented in the PowerPoint slides to discuss several sets of questions. The case is suitable for a wide range of high school and college introductory biology courses, as well as undergraduate microbiology, ethics, and public health courses.


  • Explain how the molecular clock can act as a "tape measure" of evolution.
  • Describe how emergent diseases can spread into human populations.
  • Evaluate the effects of social and cultural factors in the transmission and understanding of disease.
  • Explain how the molecular biology of HIV allows it to infect target cells.
  • Outline the steps of the HIV reproductive cycle.
  • Discuss the mechanisms of viral recombination, and explain its role in the emergence of new diseases.
  • Describe one strategy for the prevention of new pandemics.


Virus; AIDS; acquired immunodeficiency syndrome; HIV; human immunodeficiency virus; infectious disease; viral infection; emerging disease; recombination; evolution; molecular clock; pandemic

Educational Level

High school, Undergraduate lower division


PDF, PowerPoint

Type Methods

Analysis (Issues), Interrupted



Subject Headings

Biology (General) Epidemiology Evolutionary Biology Microbiology Molecular Biology Medicine (General) Public Health

Date Posted


Teaching Notes

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Teaching notes are intended to help teachers select and adopt a case. They typically include a summary of the case, teaching objectives, information about the intended audience, details about how the case may be taught, and a list of references and resources.

Supplemental Materials

The supplemental material below may be used with this case study:

  Click and Learn: Cells of the Immune System hhmi/

Answer Key

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The following video(s) are recommended for use in association with this case study.

  • HIV Life Cycle hhmi/
    A short video clip explaining how HIV infects a cell and replicates itself using reverse transcriptase and the host's cellular machinery. Running time: 4:52 min. Produced by HHMI BioInteractive.
  • Recombination of Viral Genomes hhmi/
    A short video clip showing how two different strains of influenza can infect a single cell to produce a new third strain of influenza. Running time: 3:05 min. Produced by HHMI BioInteractive.