Do you know what the Human MicroBiome is? Rather gross. In fact, the Biome can be thick enough to actually fight off other germies trying to invade you before your innate immunity kicks in.

Yes, breath is a major way of seeding the environment, but not the only one. There are other ways to shed virus and bacteria. We do it constantly. Skin, hair, clothes of a sick person are also contaminated because at home, they are not covered and their Biome is everywhere. They can transfer germs to fomites or through direct contact with others - picking up items, handing over money, gasoline nozzles, credit card keyboards, sitting on a chair. Touching or brushing up against anything leaves a trail that others can touch and you can pick up.

Years ago I did a project randomly swabbing all kinds of common objects, water fountains, elevator buttons, door handles, etc. It was fascinating what grew on agar. It's really a wonder we aren't always sick. Our immune systems, Biome, Innate, and Adaptive are really amazing.