// But did science see off Spanish flue? or did that just disappear as it came?//
yeah it did
come on come on
do you reading on that - - or did God say OK that is enough for 1919? no he didnt - it died out in the usual scientific conditions
mutated and returned in a different form
we know this because we know the sequences of both viruses and they are related
https://en.wikipedia.org/wiki/Influenza
a bit of a long read I can see why you skipped it
MERS and SARS DID just stop leaving the scientists non plussed