Good stuff so far, but why do I get the feeling this is going to be Resident Evil: Extinction-esque? lol. Hope to see more of this soon, as I'm a sucker for good zombie-survival stories with romance. ;-)

Fiddly grammatical stuff:
-Too late is repeated twice in the first paragraph
-The use of "these" in relation to societies is odd in the first p.
-Watch the placement of modifying phrases. The "land" didn't form ghost towns, the people leaving did. The "riot" wasn't one among millions of people, the mother was.
-The phrase "emerald green" would be better replaced by something less common

The good:
-Love the concept
-The names are very realistic. "Others" and "Cold ones, Dogs, Demons, the Dead" sound like names that would be attributed to the unknown.
-Good hook at the end

Best of luck!
-R