The Asteroid of the Damned
The world has just been hit head on by a large asteroid. Most of the smaller asteroids and the debris have burnt up upon entering the atmosphere. The damage to the planet is extensive. Earthquakes and volcanoes have been activated and the population has suffered massive devastation. Tidal waves and tsunami's have caused the coasts to be pushed inland. Since the asteroid actually hit in the middle of Russia. The water levels have risen exponentially since the tectonic plate that Russia sat on was busted. The Earth's atmosphere and oxygen levels are changed and 98% of the planet's population has been wiped out. What hasn't been destroyed by the asteroid's impact has been destroyed or altered by the excessive heat. Fortunately, Nature will always find a way.
The animal and plant life has changed immeasurably since the asteroid hit. Since the devastation of nearly all animal life there are new creatures that are completely new and some old ones that have adapted and now have harder skin whereas before they were furry. There are more reptiles and amphibians, and there are fewer mammals than before. The creatures are more vicious because there is less available food. People are no longer on the top of the food chain.
The people who were in the underground bunkers came out after five decades. Not all of them survived. About half died in the first week. The rest of them began to feel changes as their bodies adapted to the new surroundings. Their cells changed and adapted to the atmospheric changes in oxygen and carbon monoxide levels as well as other gases in the air. Those that survived began to get sick with something like the flu. After about a week of illness they began to thrive. It was then that they started to realize that they had some horrifying problems. Those that did not survive started coming back to life as the walking dead.
Your location is in the United States exactly where to be announced.
When they are fighting the dead, each other, the new wildlife and the planet itself, will the human race survive?