I mixed diseases. English is not my first language. Just checked from wikipedia that it has 20 million yearly cases and assumed it was the mostly harmless kids disease we all had (which is vaccinated against now also I learnt). Anyway why use 20 million cases against 44 athletes (number which might not be correct, but maybe in the ballpark)?
There is rapidly spreading outbreak of measles which makes news right now - 250 cases. Measles are that rare now
It is super contagious, so yes, prior vaccines everyone got it. Mortality is 1-3 in 1000 of sick. Plus some people get deaf and some get brain damage (dunno how many now).
So, nowadays super rare, used to be normal and harmless is not a word I would use for someone that kills 1-3 in 1000 kids.
There were also no deaths from measles for 10 years, because, well, not enough people had measles.