[If they had armies or tech at their disposal, they might be fighting still. But here they're in a state of perpetual limbo - neither capable of destroying the other. It was the perfect stalemate. Both sides waiting for the other to make a move.]

It's true that the infected would spreading disease, not signs but they don't actually want that. There aren't always advanced warnings in cases like this.

[Fire drills were usually a surprise for students at school, with the purpose of catching them off-guard.]

Zombies are the reanimated dead due to an infectious disease spread from one individual to the next, usually through biting. They are attracted to living beings who are not infected.

[Not that the Galra need any ideas but it's kind of interesting sharing something so part of Earth entertainment to any alien.]