It is not clear how they knew that S. pyogenes (please check your spelling!) was the causative agent. Was 1/11 samples positive? 11/11? Some more information on patient symptoms is needed. In addition, it is not clear that cases were different ages than the controls. Since it was unmatched, I assume that controls were selected randomly. As age is not shown as a risk factor, the conclusion that it disproportionately affected young people is not substantiated.