This is a simplified flu spreading model.
All the particles are distributed randomly (position, velocity and moving direction).
Assume only one of them is inflected at time t=0, and the color become red when it is inflected (others are shown in gray)
1. The condition to get inflected is by collision (between un-inflected element and inflected element).
The probability for gray element to get inflected when collision occurred is p. if p=0.5, it means that, on average, un-inflected element need to be collide with inflected element twice to be inflected.
2. The time for the element to develop an immune system is T.
If the element is inflected at time t, then the immune system is developed at time t+T , and it will not be inflected anymore (the color turn to green).
You can adjust the probability to get inflected [b]p[/b], the time to develop immune system [b]T[/b] , the average velocity of the particle to find out different flu spreading pattern.