[bluGill]

For many years it has been a worry of any competent military that the enemy is going to release a bio-weapon. As such every army is be preparing for something. They won't know what exactly is coming, but they have processes in place to deal with it as best they can. That means supplies in place, and people training in using them - it might mean a generic gas mask instead of a N95 filter, but it will get the job done.

The army is also well trained in securing an area. Need to enforce no travel, the army learns that in basic training.

Again, this isn't about the US army, it is about any competent military in the current world. Limited of course by their budget.