Catching a cold from strangers

Factual Questions
1

This might be more whining than a GQ.

About 10 days ago I came down with a cold compounded with a sinus infection. My wife and two kids have managed to stay healthy.

So how could I get sick from someone (I don’t even know who, possibly even a total stranger) yet the people who live in the same house, share my table, and even my bed, don’t catch it from me?

2

They could have had the strain earlier this year and are now immune…

Or…
…you and they have managed to not contaminate each other. The just have not had the virus from you successfully infect them.

It’s pretty much that simple.