When they first started appearing, everyone thought it was a stupid "Social Experiment." That was, until the first person was converted, a gruesome mess for the janitors at that mall, that's when people started to be concerned, not panicking, but concerned.
The government took care of the situation and did tests on the 'zombies' when they reviewed the infected, it seemed like the people were dead for about 3 months.
They tried to do tests on it but whatever it was it was mutating too quickly for the test to be accurate.
And then, the first escape happened, and due to the incompetence of the team assigned to capture it, they were infected and out roaming the country.
Meanwhile, the UN decided to have a global meeting with the leaders of every country, but one country didn't show up, Salman of Saudi Arabia.
So, they made an investigation and saw that the country, in short, was ruined. There were the zombies running everywhere, which made them more concerned for the U.S, where the zombies had already breached confinement.
They rushed back, but they were too late, the zombies had returned to the facilities, this time, with about 70 more zombies, however, unlike the expectations, few of them were actually dead humans, there were bears, dogs, coyotes and other various forms of wildlife.
Then, the undead moved on to the rest of the country, infecting everything it could, and this is where the story of our protagonist and antagonist starts, in school...