Infectious Disease Transmission:  A Simulation

Two of the tubes in the class contain fluid containing a mythical infectious disease. All other tubes contain normal uninfected “body fluids."

1.      Take your tube of fluid.

2.      Select a person you “trust” and “suck up” one pipette of fluid from your tube while your trustworthy partner “sucks up” one pipette of fluid from her/his tube.

3.      Simultaneously, pipette the contents into the “other” tube. (i.e., you squirt into your partner’s tube and vice versa).

4.      Select a second person you “trust” and repeat steps 2 and 3.

5.      Select a third person you “trust” and repeat steps 2 and 3.

6.      Return to your seat and hold your tube above your head.

7.      Your teacher will add the acid-base indicator phenophthalein to your tube. At pH values of 7 and below, the indicator is colorless. Over a pH of 7, the indicator turns a pink color.

8.      Swirl your fluid gently after the phenolphthalein is added. A pink color indicates that your tube has been “infected.”  No color change indicates that you have remained free of the disease.

9.      Answer questions A-C.

•     Repeat this experiment, however, this time record the names of the partners you had contact with. Answer questions D and E.

•     See if your class is going to repeat this experiment a third time. If so, this time:

I.          Place 10 drops of your solution into one depression of a spot plate after your first exchange.

II.        Add one drop of phenolphthalein to that depression.

III.       Listen to find out if you are

1)         a person who will tell all potential partners that if (s)he is infected. This person truthfully tells if (s)he is infected or if (s)he is not infected.

2)         a person who will never tell a potential partners if (s)he is infected. This person never tells if (s)he is infected. This person will be untruthful if (s)he is infected.

3)         a person who decides on his/her own whether to tell after each test.

IV.       Perform your second and third exchanges by playing that role, but do not test youself again until after your third exchange.

V.        Return to your seat and hold your tube above your head after your third exchange.

VI.       Answer question F and G.

I don't know about you, but I'm clue-less?  So, let's get started.

Questions for the lab and write-up.

A.        How many people are in the class?

B.        How many people remained “disease free” out of the class?

C.        What percentage of people in the class were infected after only three exchanges?

D.        What percentage of people in the class were infected after the three exchanges in this simulation?

E.         Compare your list of contacts with the lists of other people in the room. Who were the two original “infected” individuals in this class?

F.         How did you feel in your role after your first exchange in this third trial?

G.        What is your opinion concerning the confidentiality of HIV/AIDS testing results?  Who should have access to that information?  Explain why you feel this way.