- Reading 1 Module Introduction
- Activity 1a Infectious or Contagious?
- Activity 1b Interactive Table
- Activity 1 Discussion
- Reading 2 SARS and Zika
- Reading 2 Videos
- Reading 2 Resources
- Reading 2 Discussion
- Activity 2 How Contagious is it?
- Activity 2 Resources
A Tale of Two Epidemics
In this reading students explore two epidemics – Severe Acute Respiratory Syndrome (SARS), spread by direct contact and the recent epidemic of Zika virus that is transmitted by a mosquito vector and implicated in microcephaly in newborns and in paralysis in adults. Students consider how the mode of transmission and other factors affect the emergence of an infectious disease and its escalation from a localized outbreak to an epidemic.
Students compare the two epidemics and use information about the biology and ecology of the viruses to propose ways the epidemics could be halted. At the end of the reading students revisit the idea that diseases that are transmitted by direct or indirect contact with infected individuals are considered contagious and are introduced to the mathematical construct, R0, that enables an estimation of the degree to which viruses or bacteria are contagious. Students read more about R0 in Reading 3 and work with it in the remainder of the module.
The following tales of two viral epidemics demonstrate how localized outbreaks can escalate to epidemics by very different modes of transmission — one involving direct or indirect contact with infected individuals and the other carried by a mosquito vector. By understanding both the mode of transmission and the ecology of the virus, interventions can be developed that could stop the spread of the disease. As you read keep track in a chart or table of the characteristics Zika and SARS viruses have in common and how they differ.