Comment by Epa095

It is actually extremely common in Europe (as I linked to in a sibling chat), with 30-40% of kids having it at any time.

With those rates, my guess is that you probably had it several times, but just thought your bum was itching for no reason (or you were one of the asymptomatic cases). I think the awareness of it has gone up, now it's common to let the kindergarten know if you suspect it in your child, and they send a message to the other parents.