In order to prepar an exam, i would like to discuss about how virus spread.

I got some informations about different models, such as SI, SEI, SIR, MSEIR... and their differentiel equations

But i have some troubles to write and solve them.
i would like to use maple to modelize this propagations, but i don't know how to do at all.

Could someone give me a base, for a quite simple model such as the SI model?

Thanks

ad