"Nothing," William answered with certainty. He'd been casting some of the complex spells he knew every morning, partially because it was important to watch for symptoms and partially because the idea that he might not be able to do them scared the hell out of him.
Gabe was looking more than a bit worse for wear, and like he was only half-aware of what William was even doing here. It didn't inspire the most confidence in his potion-making or logic process, but William knew as well as anyone that they were fighting a deadline. The sick kids - and teachers - were physically ill now as well as magically bereft, and no one knew whether or not the disease was fatal. For all they knew, they could be fitting first-years into coffins before the weekend was over.
"You look a little rough," William commented, joining Gabe beside his bench. "Do you want to catch a few hours of sleep before we do this? I can come back."