Each sexual encounter will be represented by the exchange of droppers of fluid between the two test tubes. To test for HIV add a drop of Phenolphthalein. If the fluid turns pink that individual is infected. Students are visibly shaken when their subject is found to be HIV positive. Have epidemiologists following infected individuals give profile of their subject to the class.
Students move to cooperative groups.
One group could approach the problem based on the perspective of close friends, another could represent the views of the medical community, another the family, etc. Let your students help define the interested groups. It will facilitate group work if a group leader and a recorder are assigned. Write these on the group's display pad. Choose the main problem and write it on the pad as a question.