Sorry to hear about this.
For my boys childcare, whenever there is a hfmd outbreak. there is the most of 2-3 cases
I only had two times of experience with it. other then spring cleaning, it depends on how the school is managing whenever there is an outbreak.
My son's school, whether there is a outbreak (2 case and above)
They will ask parents to bring home th mattress covers and not bring any.
they will sterilised the mattress after naptime.