That's what I keep telling everyone. Each time someone walks through the front door all the bugs come back in.
It has been this way since the first hospital, dead folk in hospitals used to be classed as 'Death Unknown', but now we have names for it since we discovered these bugs.
It is not that these bugs have got stronger, or just appeared, it is our own immune systems that have been dummed down with decades of cleanliness......hence 'Kills 99% of germs' products is one way to give you kids allergies