Techland wanted to present a deeper vision of what a zombie epidemic would mean for humankind. “Epidemic” being the crucial word here. Mutating into a zombie is a result of infection, not some kind of a supernatural transformation, but simply a disease, just like flu, pneumonia, or SARS.
This realization helped us create one of the most outstanding features of Dying Light: its setting. A quarantined city just several weeks after the outbreak.