Now, here are a few possibilities for how Max might try and throw in a twist:
1. The cure backfires (or has a chance of backfiring, or can be sabotaged by nations embracing the infection), leading to a massive spike in infections in nations that research a cure.
2. The zombies are particularly durable, making the 'kill' option relatively ineffective, at least at first
3. Special Infected! Perhaps nations that embrace the infection will have the ability to create zombies that are stronger or more resistant to the cure, or have abilities that will otherwise fuck over the anti-zombie nations
For the record, I shall go with the cure option.