One of the simplest models of disease spread is the "Susceptible - Infected - Recovered" or "SIR" model. In this model, people are either Susceptible (they can get the disease but haven't yet), Infected and can spread the disease, or have Recovered. People who have recovered can either become immune (i.e. unable to catch or spread the disease) or they can die (I know, funny idea of 'recovered', but there you go... sometimes the 'R' is taken to mean 'Removed', which might be better). There is some time set before people 'recover', allowing them to spend some time infecting other people.
The program below allows you to model this situation. When you first see it, the model should have Susceptibility and Infected Times set to 100% (everyone is susceptible and take a long time to recover), and Recovery Chance set to 0% (everyone dies when the disease has run its course). For the moment, don't change these values.
This is what we might think of as the "Zombie Bite" model, perhaps the simplest disease model. Everyone can be infected, and once they have it they wander around for a long time infecting everyone else. There is no real recovery or immunity.
Click the mouse in the rectangle below to add people. The first person will be the infected person (you can add more infected people by right-clicking, but stick with one for the moment). Press the spacebar to start and stop the model. Add a few people in and see what kinds of things make the disease spread fast or slow. You can clear the model by pressing "q".
Green circle = Susceptible person
Red circle = Infected person
Gray circle = Dead person ('dead' dead, not un-dead!)
[Blue circle = Immune person (none of these yet)
Questions:
What kinds of things are important in controlling the spreading rate in the model?
What kinds of things might be important in the real world?
Go on to Part 2 where we'll look at a slightly more realistic disease.