The Infected

DX-1118 is the byproduct of the Hope, Idaho experiment in which Blackwatch scientists attempted to engineer viral pathogens specifically designed for targetting certain ethnicities. However, the original goal of the experiment fails.

At first, none of the administered pathogens harm the unknowing citizens of Hope. Viral testing on chimpanzees had shown promising results, but for months the humans of Hope, Idaho show no symptoms. The first signs of success are the "Hope children", babies who carried the virus before they were born. After birth, each child displays unique characteristics, but each subsequently dies due to health complications after only a few years. Blackwatch scientists postulate that the births are failed attempts by the virus to fully activate the human genome's noncoding regions.

Disappointing results ended in 1969 when one of the viruses mutates within the body of Elizabeth Greene, becoming the first aggressive strain of the Blacklight virus. Blackwatch allows the virus to consume the town, gathering valuable data in the process. Once the infection is complete, the military kills the entire population, but as patient zero, Greene's life is spared. Gentek is later tasked by Blackwatch to conduct research on Greene and the thousands of Blacklight variants that her body produces.

This viral research continues relatively peacefully until Dr. McMullen decides to further weaponize the virus with the help of Alex Mercer. Mercer conducts research on Elizabeth Greene, believing she is an innocent patient. When he learns that she is the victim of military experimentation, Mercer steals a sample of the weaponized virus he helped create and unleashes it at Penn. Station on Manhattan Island.

The Blacklight virus is highly adaptable and continuously evolving. As such, it may take many forms.

Walkers are the most typical and numerous form of the virus. Humans that contract the virus are transformed into shambling, zombie-like creatures that are initially of little threat. As the infection continues to transform the host's body, however, a walker may grow weaponized appendages and increased physical strength and speed.

Hunters are large beasts that work in packs to subdue their prey. While generally humanoid in appearance, whether or not they are grown from human hosts is unknown. Regardless, their development takes place in large sacs located within hives and water towers.

Leader hunters are a larger variant of the standard hunter and assume a leadership role among the pack, coordinating and directing their efforts. More resilient than their lesser brethren, leader hunters possess two brains and two backbones, allowing the backup parts to assume primary functions as the damaged organs regenerate.

Supreme hunters are as mysterious as they are powerful. Only one is known to exist, and unlike other infected, it is capable of speech and more independent thought.

Unlike all other infected listed previously, runners are purposefully made to appear as human as possible, allowing them to avoid detection by uninfected. They are also distinguished by having extraordinary physical capabilities as well as minds powerful enough to direct the hive mind that governs the lesser infected created by the runners. It should be noted that documented runners have always been female until the discovery of Alex Mercer, who is believed to be some sort of runner variant.