In The Last Stand: Aftermath, there isn't anything that can be done for you: you're going to die, but it's up to you to decide how you're going to breathe your last. You'll choose your survivor and explore a destroyed civilization, finding fuel and gathering supplies to craft weapons and whatever else you might need. You'll also become more powerful over time, receiving mutations such as Bulk, which will increase your melee damage by 25% and decrease your movement speed by 10%.
However, no matter how powerful you become, you'll eventually die to your infection, and when that happens you'll start again as a new survivor with perks and upgrades based on your last run.