“not sure if they died by sneezing though”
That’s from Pirkei d’Rebbe Eliezer.
But again, the point is that they died suddenly–with just a sneeze, not that people would randomly die as soon as they sneezed. In fact, that is the opposite of the main intention. The Gemara and Medrash are describing a world in which people remained healthy, and it is being taken to mean that people got sick easily.