I really don't think, for me at least, it's about a lack of contact. I have had one illness in 30 years, during the best part of my remission, that may have been the flu. I have had no colds but have had laryngitis several times - almost always following inoculations. I have been surrounded by and in contact with people with colds and flu and nada, zip, zilch for 30 years. I did come down with a febrile illness marked by a rash, particularly noticeable on my face but also on my body, and swollen glands on the back of my head where I had no idea I had glands, within the first couple of years but it was not a flu or cold. I have had years of sore throat and swollen glands - less so in the past ten years but not gone. I have had many bacterial infections, some odd and some very stubborn. But, only one or, perhaps two, new viral illnesses - as opposed to reactivation of Herpes viruses, has declared itself in 3 decades. I think that is so odd! Must say, though, I'm not complaining!