This document provides instructions for a classroom activity to simulate the spread of a disease through an exchange process. Students are divided into volunteers and two start as infected. Through multiple exchange rounds, where the contents of cups are poured between partners, the number of infected students doubles with each round, demonstrating how diseases can spread exponentially through a population. To identify the initial infected individual, referred to as patient zero, indicators are added to samples to detect infections and trace the spread back to its origin.

1. Tracing an Epidemic Davidson Students Volunteer for Science 8 th Grade – Lab 2

2. Introduction Bacteria, viruses, protists, and prions cause diseases. Strep throat, tuberculosis are caused by bacteria AIDS, measles, chicken pox, mononucleosis Malaria Mad Cow’s Disease Epidemic vs. Pandemic Pandemic affects larger, global population Spread of epidemic Airborne Waterborne Exchange of body fluids Positive and Negative samples Positive has disease-organism, Negative does not Indicator

3. Background Info

4. Background Info

5. Pre-Lesson Setup For Demo #III: Match up the eight numbered cups with the numbered bottles. Make sure bottle C-8 is emptied into cup 8 (0.025 M NaOH). For Demo #IV: Fill one cup about half-full of water for each student. For Patient 0 (DSVS member), empty 1oz bottle of NaOH in another 3.5 oz cup.

6. Demo #III: Testing For a Disease Add “contaminated” liquid and clean liquid to two different 6 oz. cups. Add four drops of indicator phenolphthalein to each cup. Pink – INFECTED; basic (sodium hydroxide) Clear – NOT INFECTED

7. Exp #IV: How Does A Disease Spread? Need six volunteers. Two DSVS members will also participate. Write the exchange sequence chart on the board. Pass out the numbered cups. Cup #8 goes to DSVS member. Follow Exchange Sequence Chart and exchange with partners. In “Exchange,” pour all of one cup into the second cup. Then pour half of the total liquid back into the first cup. Inform the students that #8 was infected. Predict who else is infected. Add a few drops of the indicator (phenolphthalein) to ALL the cups. The solution in cup #8 will turn pink. Continue 2nd round of exchanges. Number of infected doubles with each exchange. Ask how many exchanges would infect a classroom of 30 (5 exchanges) Exchange Sequence #1 Exchange Sequence #2 Volunteer 1 Volunteer 5 Volunteer 1 Volunteer 2 Volunteer 2 Volunteer 6 Volunteer 3 Volunteer 4 Volunteer 3 Volunteer 7 Volunteer 5 Volunteer 6 Volunteer 4 Volunteer 8 Volunteer 7 Volunteer 8

8. Exp #V. The Disease Spreads Pass out prepared cups half-filled with water and empty 1 oz. cup to each student. Tell students to set aside a small amount of liquid in a separate cup as “uncontaminated” control. Write their names on the top line of their observation sheet. Write name of “exchange” partner. In “Exchange,” pour all of one cup into the second cup. Then pour half of the liquid back into the first cup. Continue 3 rounds of “exchange.”

9. Exp #VI. Identifying Patient Zero Test liquid by adding several drops of indicator, phenolphthalein. Ask all students to stand up. Ask all participants with an uninfected (clear color) sample to sit down. Ask all infected participants (pink solutions) to bring their observation sheets and come to the front of the class. Ask the group at the front of the class to look around and see if they exchanged with anyone in the group in the FIRST exchange. If they did not, then they should sit down. Only two participants should be standing. One of these participants is patient zero. Ask these participants to bring their the original uncontaminated liquid to the front of the room. Add the indicator to the liquid in each of these 1 oz cups. The one that turns pink identifies patient zero.

10. Optional #VII: Tracing the Spread Ask the carriers to stand. Ask who exchanged with them during the first round. Ask those who exchanged with the people standing in the second round to stand. Ask those who exchanged with the people standing in the third round to stand.

11. Wrap-Up Clean-Up: Dispose of liquids in a jar or down the sink. Discard all used cups. Topics of Discussion: Vaccines and Cures Famous epidemics Black Plague in Europe Smallpox in North America Tuberculosis Influenza Pandemic of 1918-1919 Credit: Vanderbilt Students Volunteer for Science