It is the year 2011, one year after the apocalypse.
It all started with a batch of tainted influenza vaccines. Come autumn or winter of the year 2010, when everyone was going out to be inoculated against the seasonal flu and Swine Flu they were unknowingly infecting themselves with a mutated and deadly form of the virus. After merely days after their first exposure, the infected began exhibiting strange behavior. Along with nasty bodily aches, vomiting, and other typical symptoms of ordinary influenza, the infected became hostile to anyone that might pass their way. They certainly didn’t make a conscious decision to spread the mutated virus, but by way of scratching and biting they sped up the demise of the human race a great deal.
The world descended into chaos. As they say, the road to hell is paved with good intentions. All people wanted was to contain the disease and eventually find a cure, but all they succeeded in doing was forming angry mobs. There were so many unnecessary deaths and not exclusively from the mutated flu. World governments ceased to function and the population thinned out to an extreme degree.