This visualizes a highly simplified model of the early stages of the SARS-CoV-2 virus epidemic and how likely it is to spread to the SF bay area.
You can modify the parameters while the simulation is running. Of most interest to me was what happened when you drop the rate of spread from Wuhan to SF (set mu=0). There's a time window after which stopping flights is too late. Read the model description here.
The javascript code solves the following equation using the forward euler method with a quirky little hack to load people onto planes as part of the animation.
If you want to see this problem analyzed in more depth, check out this project on github