I do not adhere to the 6 (or isn't it now 10) per day:). Hence I eat little fruit but wash all fruit and veg before eating, unlike the wife who is a bit of a kitchen *** in secret. So my diet is mixed: part washed & part "unclean" but I don't care.
Why wash? Pesticides! We were once warned to wash fruit/veg using Washing-up Liquid! as the the pesticides etc were wax-coated in.
Moving on..
Low to moderate exposure to germs and viruses is a good thing. It is not about "toning up" the immune system, the immune defence REQUIRES such exposure in order to learn about the environment in which we live and act when required. It's the basis of man-made immunisation/vaccination which only mimics nature.
That does not mean exposure to any type of dirt is good - dog and bird poo are bad.
As regards hospital infections, I believe these are mainly caused by visitors who in toto shed skin cells by the milligrams if not grams in a day. There is much ado about cleaning in hospitals but what needs cleaning away? Dust or if accumulated, dirt. This is mainly composed of dead skin cells but the same detritus still harbours staph and other bacteria. Visitors do not know what elbow-taps are for - elbows, not hands!
SIQ.