Runner is the codename assigned by Blackwatch to non-Prototype Infected individuals who had managed to escape military detainment. These infected individuals are capable of manipulating and spreading the virus they have been infected with. 
Although Runners can be classified as a variant of the Infected, they differ from the walkers. A Runner's physical features and intelligence are not affected when they are infected with a viral strand, similar to a Prototype.
However, little is known about the exact behavior of Runners. They seem have a certain innate ability to control the infected individuals to a certain extent. Their physique is drastically enhanced to physically overpower a Prototype.
Also, according to a Web of Intrigue node, all Runners are female. Genetic differences between genders probably impede males from developing Runner traits and mutations.
- Main article: Elizabeth Greene
Elizabeth Greene was a Runner infected with the Redlight virus during Blackwatch's experiments at Hope, Idaho. She had a great state of command over other types of infected and was capable of controlling the whole town of infected Walkers for over a year.
When she was released at Manhattan by Alex Mercer, Greene started to spread her own strand while creating new forms of infected creatures. Like in Hope, Greene was able to control these infected except Mercer. She was also capable of infecting everything she touched, even non-organic materials, making her extremely deadly.
An unnamed runner is mentioned by Cptn. Robert Cross during a debrief to his soldiers. It is unknown how she was infected, or managed to escape from Blackwatch. This Runner evaded being captured for three weeks, during which she infected a town called Two Bluff.
- Although Alex Mercer is referred as a Runner by the ground forces on Manhattan Island and Dr. Raymond McMullen, Mercer does not display any of the symptoms of the previous Runners. This reference could have been due to the lack of knowledge of Mercer's capabilities and differences.