Even if you eradicate all the infected, the disease might come back somehow. You need a cure to prevent this disaster to happen again ffs. He had the chance of earning titles and shit but nooooo he decided to have fun instead.
@RiceNipple
I agree. Killing everyone would solve it only for a moment. There were many diseases that were supposedly eradicated but came back. No virus is completely dead even after his hosts died. It may simply hibernate and strike back later when the conditions are right.