sueDonim re. family members. Could it be something to do with lifestyle.
Families tend to have a similar diet, may smoke, etc. My family eat quite healthily, exercise regularly, don’t smoke. That gives us a head start.
I honestly don’t know! I know families who’ve all been exposed to CV yet only one person has developed symptoms and no one else had caught it from them, either.
It’s probably as mysterious as to why my brother never had any of the childhood diseases the rest of us four children got, apart from having Rubella. He didn’t even get chickenpox when his wife and two daughters all had it at the same time. If only they could bottle whatever is in his immune system.