In 2050 a drug company conducted experiments
on humans by mixing the medicine to the mineral water and turns into a virus H45BY, because humans have much to consume
mineral water is to pass the virus spread H45BY.
And The drug companies that immediately makes the serum so that the virus doesn't spread more widely.
This virus can make people die, but they can be revived into zombies, and they (The Zombies) try to destroy the virus serum which can counteract H45BY.
There are 5 soldiers who tried to save the serum, but now only left one, because the other four has turn into zombie.