I'm trying to work out the idea of a rodent-borne illness, reminiscent of the plague, but nixing the fleas. The disease has wiped out most of the population of large city and its surrounding area, and would have wreaked havoc on the rest of the world were it not for its timely quarantine. So, how was it quarantined? It needs to be impermeable to the rodents themselves as well as airborne pathogens, and also it should cut off the remaining humans stuck inside from the rest of the world. My initial idea is a sort of dome, but that's not a very convenient or efficient route, and it reminds me too much of the Simpsons movie... . Any ideas?