Are you suggesting that bringing more air from outdoors into our indoors environments will cause us to lose our ability to tolerate outdoors air?

Not to worry, people will still have children, and I assure you, they'll still go out into the world and lick the doorknobs/each other and get you sick so you can bring it to work.

> Can you catch airborne respiratory diseases from eating fruit?

I'm willing to speculate that exposing our immune system to surface pathogens helps deal with airborne pathogens.