3 Viruses Go "Viral"



Module 2, Seeking the Cause, explores the three major ideas in epidemiology: identifying the first case of an outbreak or epidemic (Patient Zero or index case), determining the causative agent, and tracking how a disease spreads.

The purpose of Module 3, Viruses Go “Viral”, is to examine in greater depth factors that result in outbreaks and epidemics. Students explore the biology and ecology of viruses that determine the origins of a new, emerging diseases. They examine the characteristics of a virus and its hosts that impact whether an outbreak will remain confined to a local area or result in an epidemic or pandemic.

Students begin by examining the difference between a pathogen being infectious and being contagious in a categorizing activity. Based on this activity, they identify different modes of transmission of infectious diseases. Students read about the Severe Acute Respiratory Syndrome (SARS) and identify the factors involved in its emergence and spread, then compare its spread to the most recent epidemic caused by the Zika virus. Students predict, based on certain parameters including the reproduction rate (R0) of a virus, whether a viral outbreak is likely to escalate into an epidemic.

Students then determine the impact of vaccination on a measles outbreak and prepare for a mock town meeting in which they must decide whether the Department of Public Health in their city should enforce a stricter vaccination policy that would require all children to be vaccinated against childhood infectious diseases.

Learning Outcomes

At the end of the module student should be able to:

  • Explain what is meant a contagious disease
  • Describe different modes of transmission of viruses and relate these modes to the spread of the disease
  • Explain the meaning of R0 and compare the R0 of different viruses
  • Describe the limitations of R0 in predicting epidemics
  • Calculate the theoretical percentage of individuals that need to be vaccinated to prevent the spread of a disease and determine the effect of insufficient numbers of individuals being vaccinated on the spread of a disease
  • Define the principle of community (herd) immunity and describe the requirements for it to be effective in preventing the spread of a disease
  • Explain the role of vaccination in disease prevention and analyze the arguments for and against vaccination using evidence
  • Discuss the ethical issues related to vaccinations

Assumptions of Prior Knowledge

  • Students know the differences among an outbreak, an epidemic, and a pandemic of infectious diseases
  • Students are familiar with viruses as agents of infectious diseases
  • Students are aware that an infectious disease can be “caught” by close contact with an infected person or from contaminated food and water. They may know that insects and other animals can also transmit disease.


Below are a list of materials for each activity in this module.

Activity 1: Infectious/Contagious?

  • One copy of the Disease Chart for each pair or team of students.

Activity 2: How contagious Is it?

  • If you want to provide information on vaccinations for students to initiate their research for the final report, make copies of the following readings, one for each student:
    • Role of vaccinations
    • Pros and cons of vaccines
    • Key ethical issues related to vaccines
  • If students are presenting the highlights of their reports, provide poster board and markers.