The irony is that the best way to change building ventilation systems to avoid spreading germs is to do the opposite of what the greenies have been forcing down our throats for many years. In current technology, a typical office building (and probably also a typical school) ventilates occupied rooms with a mix of aout 20% fresh air from outside, and about 80% air that's recirculated from within the building. If that 80% is contaminated with germs, there are basically two ways to deal with it:
(1) Don't recirculate it. Exhaust it, and supply 100% outside air. That means a massive increase in energy use for heating and cooling. Or
(2) Put HEPA filtration into the recirculation system. That reduces the efficiency of the system, requiring (probably) more powerful fan motors and significantly more frequent changes of filters.