Kindergarten plague - otherwise known as daycare plague, pre-school plague or even creche plague - is a regrettably familiar experience to most parents in the Western world. Other parts of the world, where family patterns are different, probably have their own equivalents.
Definitionally, kindergarten plague is a term used to describe any infectious disease transmitted to parents from their children as a direct result of the children having been infected with the disease at their kindergarten (or daycare center or pre-school or whatever).
Small children, being much more uninhibited, tend to transmit diseases among themselves with carefree abandon (unlike adults, who will usually politely turn their heads away before coughing).
My personal experience with kindergarten plague covers the full gamut from the most common respiratory diseases, over bacterial infections (the entire family is on antibiotics, recovering from a dose of Type A streptococci), to viruses. In particular, Coxsackie virus flourishes in the Western world chiefly as an infection among small children, transmitted as kindergarten plague. And yes, I've had that, too.