# THE SPREAD OF AIDS

Ellen Averill
1993 Woodrow Wilson Biology Institute

## INTRODUCTION

This is a hands-on activity that simulates the spread of a disease such as AIDS. Students will become aware of the rate at which AIDS can spread within a population.

### TARGET AGE/ABILITY GROUP:

Secondary level, all ability levels

40 minutes

### MATERIALS:

1. bathroom (paper) cup/student
2. disposable pipette/student (If pipettes are unavailable, students can carefully pour a small amount of the liquid between cups.)
4. 10 ml of 0.1 M NaOH for one student who is the only one to be a carrier/class (0.4 grams of NaOH dissolved in enough water to make 100 ml of solution) or 10% solution of Liquid Drano (10 ml of Drano plus 90 ml of water)
5. 10 ml of water each for all other students
6. phenolphthalein solution in dropper bottle or with a pipette (indicator for basic solutions)

## TEACHER GUIDE FOR PREPARATION OF MATERIALS:

For each 24 students, select one student to be the "carrier"; this student will receive the cup with the 10 ml of NaOH solution. Do not tell this student that the contents of his cup are different. From this one student, a maximum of 12 other students can receive the "infected" solution. Into all other cups put 10 ml of water.

## TEACHER PROCEDURE

:
1. Hand out cups and pipettes (optional); one student gets "infected"cup and all others get water.

2. After students have made exchanges of fluids, walk around and pipette several drops of phenolphthalein solution into each student's cup.

## STUDENT INSTRUCTIONS:

1. Students are to transfer "body" fluids three times by using pipettes to exchange a small amount of liquid between cups with three other students.

2. Keep track of those students with whom you exchanged solutions by writing their names on your paper.

3. After three exchanges are made, teacher will put indicator solution (phenolphthalein) into each student's cup. A pink color indicates infection.

4. Those students whose solutions changed to a pink color should determine from whom they received the "infection" (really the NaOH solution).

* Eventually the class can determine the one student who had the original "infection."

## CLASS DISCUSSION:

1. Determine the number of students who had pink solution in their cups at the end of the activity.

2. Calculate the percent of those students in the class who have the "infection".

3. Make a drawing to show the pyramiding effect of the spread of the "infection" within the classroom.

4. Discuss reasons why diseases can spread so quickly and ways to control the spread of diseases such as AIDS.

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