These aren't rules as such, but I do want you to follow them, and some facts you need to know.

Everywhere is covered in mud, sand and forests.
The weather can change suddenly. One minute it could be boiling, the next it could be chucking it down with rain.
There's no cure.
Most buildings have been knocked down by the sudden change of weather, but most of some buildings still stand. There may even be a full building standing every so often.
The animals can be killed in various different ways (main being the broken neck or shooting it/hitting it in the head).
I'm going to give my first ever age rating on this: 14 year olds and above (the chars not the RPer).
I suggest that you make two to five chars at the beginning, so your char isn't alone until they meet up with another persons char.
The virus is in the animals blood and saliva.
If an animals blood entered the system of a human they will die.
It takes 24 hrs for the virus to compeletly kill a human.
It attacks them like the flu. After a few hours they cant walk.
Animals are the carriers or the virus.
There is something in their blood (which humans dont have) which the virus attacks. Cos it isn't in a human, the virus attacks the whole body.

THIS IS FAKE, THIS HAS NOT HAPPENED AND PROBABLY NEVER WILL!!