Quarantine logic flaw?

[yuliamath]

Thank you for the beautifully executed, informative and engaging game! I am planning on using the website as a demonstration this summer in a math summer camp for high school students.

I am puzzled by the fact that any healthy node can be quarantined, not only the ones who have a direct contact with an infected node. This makes it very easy to ‘beat’ the game: regardless of where the infection starts, it is straight-forward to disconnect a large piece of the graph from the impeding infection. This is also not realistic, as usually only the people with a direct contact to an infected person are quarantined.

Is it possible to change the code so that only nodes neighboring an infected node can be quarantined?