The Virus

The Virus are unnamed bio-engineered virus that become responsible for zombies outbreak

Origin
The unnamed and unknown virus is a deadly artificial mutagen developed presumably untintentionally by Seok-Woo and his co-worker. This mutagen created by the Biotech company has resulted the contamination of natural water and first infected the animals like the deer in the opening scene which reanimated after being ran over by a truck. The virus then shortly and quickly spreads to the cities of Seoul and then throughout the rest of South Korea. The Korean military established evacuation centers in Daejeon and Busan. However, Daejeon never stood a chance and became overran by the infection then Busan is the last city standing among the rest and becomes a successful evacuation center for refugees and survivors.

Symptom
The virus spread through bites or scratches and then it takes the victim a few seconds or possibly minutes to become infected. Possible injection of infected blood or bodily fluid may contract with the virus. The symptoms of victims prior to infection are convulsive seizure and twitching. After infection, the infected may hunt down another uninfected victim with their ferocious speed, agility, and with a mob mentality. When the infected are bunched up as a horde, they have a tendency to trample or run over each other just to chase down an uninfected victim. There's no possibility of a cure or an infected victim becoming an asymptomatic carrier.