This post is merely a tot of pre-Christmas speculation.
Suppose a virus such as the common cold virus were to mutate such that the symptoms it causes become generally less pronounced and less problematic for daily life.
The obvious advantage for the virus is that we are more likely to carry on mixing with other humans and so spread the virus more widely. Staying at home for a few days does not favour virus propagation so the new strain is preferentially selected by our behaviour.
Maybe this would lead to a more widespread general and persistent level of minor debilitation. Not enough to be noticed because symptoms are generally too minor to be presented to a doctor, but enough to cause general wellbeing to sag a little.
There is already a large amount of information on subclinical infections, but how would we deal with them if they became more prevalent and more subtle in their effects? An endless series of mass vaccinations? Probably not, because how would we know they were needed?
I’ve no idea if this is a significant issue or not, but suppose it is. What if it were to occur for a number of common viral and bacterial infections such that minor debilitation becomes endemic? What kind of symptoms might become more common?
Maybe we’d just sit in front of the TV and get fat.
Perhaps we’d think less clearly even though we are still able to get on with the daily routine well enough.
Perhaps we wouldn’t be as dynamic and decisive as we were a few decades ago, but the difference isn’t noticed because everyone else is subject to the same low-level infections.