Caro - there are couple of situations where a parent is not to know that there child is sick and passing on an illness. Some illnesses are passed on before symptoms are shown and other times a child can be healthy in the morning, but wake of from their nap feverish and ill (has happened to me). I certainly believe most parents do the right thing and keep their child at home when they are ill, it is hard to blame them when they don't realise that their child is going to be ill later that day.