In this model, students are modeling the effect of HIV on a community and the ways in which it can spread through the community.
The students began by identifying the different stages of a normal person's life, and placed these into the model. First, they are born, then they are children; they grow up, and become adults. After growing old, the adults will die.
Now that this has been established, the students established a birth rate, a death rate, childhood years, and life expectancy. Childhood years was defined by the students as the number of years a person lives before engaging in 'risky behavior' or sexual behavior, which causes them to be susceptible to HIV.
The students then made the STELLA model for HIV. A certain number of babies are born. There are two places in the model where babies can be born. One of which is the babies born from normal mothers. The other are the babies that are born from mothers with AIDS. A percentage of these babies will also have AIDS, while the other percentage will not. Those born with AIDS are then placed into the 'Infected' group of people. Those born without AIDS will grow up and when they begin 'risky behavior' they will become adults. From there, they will either suffer from their risky behavior and become infected from HIV or they will die a natural death. Those who are infected with AIDS will most likely die from the disease.
After completing the model, the students analyzed the model using graphs and tables, comparing the total population with the AIDS population. They also changed the rates to first model a known population in Swaziland, then to experiment with different birth rates and death rates of other countries.