Many people walk around with a mild sniffle, mild cough, and with kids with such mild symptoms. Even when I am going out of my way to be hyper sensitive to such things, I might notice a mild sniffle or cough in my kids only while we are out and about. But those times, when I can I abort mission and go back home.
A couple of different things stacked up 3-4 years ago that made us much more cautious.
First is we had strep throat, and were on antibiotics for more then the required 24 hours, and feeling much better. We went to visit some cousins, and did not think much of it, we were medicated and feeling better. Only months later did we find out that poor cousin was hospitalised because she was infected with strep throat that has already been exposed to antibiotics. Now we will not leave the home for five days if we are on medication, we do not trust the 24 hour rule at all.
Second is that our real good friends the Andrus's had a daughter that was immuno suppressed, she could turn any minor cold into phenomena. From that experience we stopped going out for even minor colds.
Third, I educated myself on immunizations. I learned that many of the more mild sicknesses actually had a poor track record with their immunization. Many people think they are immunized for a sickness, but are not. Because of this they are less concerned, and do not notice when they actually carry a more sever sickness. I chose not to immunise for these sicknesses that could be cared for well by modern medicine. Instead I educated my self real well about symptoms and cures. When whooping cough was going around, and many people I knew were walking around, feeling mostly fine, but spreading whooping cough, I knew. As soon as we got whooping cough from people who did not know they had it, I called everyone we had been around and told them. I did this because all sicknesses incubate and are spreadable before you know you have them. Of course, at that time it looked like we were the ones who were spreading it, and the ones who were careless about being sick... sigh...
I know that even a mild cough can be the start of a major sickness, it just has not shown its strength yet. We have missed many family functions, church days, and other events because we were "sick". This creates a number of misunderstandings. Most people only stay home if they are really sick. Because we stay home for all mild sniffles and colds, people start to think we are really sick all the time. Sigh. Oh well... I still would rather error on the side of caution, and let the misunderstandings happen. We are not super humans, we do get sick, our younger kids do get the average sniffle and cough. If we are exposed we tank up on herbs, and mostly can overcome the sickness faster then average. But the truth is, yes, we do get sick.... If we are above average in something, then it is that we are above average in being careful not to get other people sick.