The cold virus has a very distinct odor when a person nearby is contagious . I didn’t notice it until we were in a restaurant and my husband pointed it out. I’ve smelled that particular odor before, but I never put two and two together and figured out that it was the cold virus.
Anyway, we were kind of trapped in that restaurant because our pizza hadn’t come yet, but we both started feeling sore throats and colds coming on by the next morning.
In general, I don't worry about that. Humans have a built-in immune system and mine seems to be working quite well as I can't even recall the last time I had a cold or sore throat. The last time I had the flu was 1969 or so and have never gotten a flu shot. I haven't gotten Covid or any of the respiratory diseases around.
Merely from breathing? Meh, that’s child’s play. I have spent practically all of my adult life honing my immune system to handle that and much, much more.