Even if we wore masks now, it wouldn't change the fact that people are already affected. Besides, we'd have to fit the entire city with masks as is and that's assuming that this is affecting us only by inhaling it. Mist is the formation of tiny water droplets and our skin is naturally porous. It's just as likely that we're going to be affected because of that.

[Newt continues walking, but glances at Aziraphale.] It isn't a bad idea to perhaps be ready for the future though. Once we know what it is, we can hopefully learn how to prevent it so that this doesn't happen again.

[And it would really help with everyone who transformed also having a lot of behavioral issues. Theseus will definitely have to keep Newt in line. The way that people look at them with disdain gets the usually gentler Scamander to bare his teeth; a low growl from his throat. At the very least, he isn't outright attacking them, but that isn't to say he won't if he feels like they're being threatened.]