The United States and the United Kingdom are lost to the necrotic plague.
Europe, desperate to keep the disease from its shores considers the most drastic of measures: nuking the US and UK to eradicate the disease entirely and start over.
Meanwhile, pieces move around the puzzle inside the States until we learn that Necrosis has a natural course that, if we leave it alone, will reach a new evolutionary equilibrium instead of devolving into mindless biting and chaos.
But if we let necrotic nature take its course, will there be any uninfected left to survive it?