One virus. Three weeks. Millions dead.
Manhatten, 2008. Alex Mercer, head researcher of Project Blacklight, died while releasing the Blacklight virus in a subway station. The extremely infectious virus quickly spread. Not only mutating infected humans into hostile mindless drones, it eventually spawned deadly creatures. Blackwatch, an elite military defense force as well as the secret bioweapons research division that had created the virus, quarantined the city. Their efforts were initially thwarted but then later helped by a creature Codename: Zeus - a portion of the Blacklight Virus that had infected and then remade the body of Alex Mercer into a sentient viral entity with superhuman powers. The island was eventually saved, but the bodycount was high. The ruthless if not corrupt Blackwatch still continues its amoral experimentation, and the being calling itself Alex Mercer is one of the few individuals with the knowledge and ability to keep it in check.