Strep 4x in one year ???

My 2.5 year old has been in daycare almost a year now. Winter was rough he had everything bronchitis strep ear infections whooping cough with strider twice ... I get kids get sick the first year but it’s now summer and my son has strep for the 4th time in a little less than a year ...

At what point would you think it’s the daycare being negligent with cleaning ? Or is this still normal ???