Pepperup Potion

Harry heard another sneeze from Hermione, sitting by his side at the table they were sharing in Potions. Then, he heard Draco's, his nemesis, sitting in front of him. And he knew that what was passing through his head was unlikely, but he could not help but find the situation very strange. Wasn't it rare that only Hermione and Malfoy were sick, and with almost identical symptoms?