Teaching High School Students About Transmission of HIV: A Little Experiment

by James L. Gallarda, Ph.D
Abbott Laboratories

The topic on which I planned to speak was HIV. First I told the students we were going to conduct an experiment to demonstrate how an infectious disease such as HIV can spread quickly through the community. I asked volunteers to hand out to each of the 50 students in the room a test tube of what appeared to contain water. (Actually 49 of the 50 tubes held water and one contained a dilute solution of horseradish peroxidase). I told them that the first part of this experiment required them to mix about one-half of the contents of their tubes with that of their neighbor and that this could be repeated with as many neighbors as they choose. I said, "OK, I have a stopwatch and you have only three minutes to do this part of the experiment. GO!" Without any delay there was a mad flurry of activity.

After three minutes had elapsed, I stopped them and said, "One of the original 50 tubes contained a substance which for the sake of this experiment we'll call an infectious agent." They all looked at their tubes and couldn't see anything different about them. I then told them to further suppose that a new test had been developed which allowed us to identify this infectious agent and determine the extent of the "epidemic." Some volunteers handed out a second tube that contained a substrate for horseradish peroxidase, and on the count of three, everyone was to test the contents of their own tube by mixing it with the contents of the second tube. A "GASP" filled the room! The tubes of those students that had come in either direct or indirect contact with the "infectious" sample immediately turned an olive-green to black color. The incidence of this disease that originally affected 2% of the population (1/50) had increased to 64% (32/50).

The analogy to HIV infection in the United States was immediately appreciated by these students. This led to an hour-long discussion of HIV, immunology and epidemiology. The students were on the edge of their seats for the entire discussion. What was most rewarding, however, were the students who stayed after the seminar wanting to know what it was like to be a scientist. I told them it was great!