A Science Odyssey Title Medicine and Health In-Depth Investigation Title

Disease Detectives

Overview: Simulate the spread of a disease and locate "patient zero"
Learning Goal: Understand some factors that affect the spread of disease and the challenges of epidemiology
Video Link: Bubonic Plague or The Role of Modern Medicine


From bubonic plague to AIDS to the Guinea worm parasite, scientists and public health officials have struggled to understand and contain the spread of infectious diseases. Using common laboratory equipment, students can simulate the spread of a simple imaginary disease in order to explore some factors that affect the rate of infection and the difficulties in tracing the path of transmission. Following the activity, have students view one of the video segments and discuss the importance of tracing an infection's roots.

Procedure 1 subtitle

Simulating an Epidemic

  • test tube and dropper for each student
  • distilled water
  • 0.1 molar NaOH
  • phenolphthalein solution, dissolved in alcohol and diluted in water (pH indicator)
  1. Let students know they are going to model the transmission of a disease by exchanging some of their test tubes' contents with that of other students. Mention that one of the test tubes is "infected" with an imaginary infectious disease. (Prepare the test tubes prior to class: Fill one tube halfway with 0.1 molar NaOH; fill the rest of the tubes halfway with distilled water.)
  2. Distribute prepared test tubes and droppers randomly to the class. Make a mental note of who receives the test tube containing NaOH.
  3. Have students walk around the room with the test tubes. When you say "Stop!" each student should use a dropper to trade a drop of fluid with the person nearest them. Repeat until at least three trades have occurred.
  4. Now it's time to test for the imaginary infection. Put a drop of phenolphthalein in each test tube. If the fluid turns pink, the test tube is "infected" with NaOH. How many students are now "infected"?

    CAUTION: Sodium hydroxide (NaOH) and phenolphthalein can irritate the eyes and skin. Alert students to avoid spilling.

Procedure 2 subtitle

Tracing the Source of Infection

  1. Now that a portion of the class has been "infected" put students in the role of epidemiologists. Their challenge is to collect data that will help them trace the path of the epidemic and locate the original carriers.

  2. As a class, use the data to try to deduce which individual was the original carrier of the disease. Why might it be important to locate the source of infection? What difficulties arise in trying to collect and interpret data? Note that the simulated disease has a 100% rate of infection that appears immediately under testing. Some infections, such as AIDS and chicken pox, can remain dormant in the body for a long time. Others, such as Ebola, kill the host rapidly. How might each of these factors affect the spread of disease and the ability to identify carriers?

The Value of Discovery
One of the greatest discoveries in the fight against infectious disease was penicillin. Alexander Fleming, who found the mold that later became penicillin, saved a sample of the original mold. He eventually gave it to a colleague at St. Mary's Hospital in London. That colleague died in 1970, and his son recently auctioned off the sample for a surprising $25,300 to the Science Museum in London!

For results for this activity, click here.
Medicine and Health Program Contents

Activities subtitle

Public Health Task Force
In Dangerous Times
What Happens When . . . ?

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