One-shot solution

Shi Ningqing was surprised because her roommate seemed to have similar symptoms!
"I've taken cold medicine." The girl said quickly, thinking that it would not worsen into something like pustules.
"Ordinary cold medicine has no effect."Andrew Qi shook his head. This was true because this time it was not a cold at all, but a plague, and a very serious plague at that.
He Shifang next to him sneered, "Haha... keep pretending! If the cold medicine doesn't work, what else do you have?"
Andrew...