Here are a few extensions to the virus.nlogo model.
Contagiousness and resistance can be sums of several
components. For example, resistance to a virus might be the sum of a turtle's
diet, exercise, and self-esteem. The contagiousness of an idea like religion might
be the sum of the penalty for not adopting the idea (Hell) plus the reward for
adopting the idea (Heaven). By allowing the user to control these components,
users can experiment with the effectiveness of, for example, different
government policies to prevent the spread of AIDS.
We can add evolution to the model by having turtles
reproduce asexually at the end of some fixed life span. We assume a parent
passes the infection to her offspring (e.g., by cultural transmission or
through amniotic fluid.) Having a non-fatal virus may confer an evolutionary
advantage or disadvantage. This could model the survival benefit of an idea
such as knowledge of a secret hunting ground. We can then compare
contagiousness (adaptation) with evolutionary advantage as ways of spreading a
virus.
The model can be extended by adding a virus attribute to a
turtle indicating which of several competing viruses (A, B, C, etc.) the turtle
is infected with. We assume a turtle can only be infected by at most one virus
at a time. Viruses can differ in their virulence and contagiousness as well as
the inital percentage of the population infected with each virus. This might be
a good model for comparing advertising campaigns for competing products, for
example.
Transmission of the virus can be made more interesting by
considering the numbers of neighbors infected with viruses A, B, C, etc. Which
virus will an uninfected turtle acquire? More interestingly, we can explore
rules for one virus replacing another in a turtle that is already infected. For
example, virus A might be a fatal disease while virus B might be a proposed
vaccine for curing the disease caused by A.