The zombies in the original Left 4 Dead series were known as “The Infected,” but the survivors in the game called them zombies. The cause of the infection in the original Left 4 Dead series is unknown, but it was an influenza-like disease known as the “Green Flu” virus.
The Zombies In Back 4 Blood Have A Different Name

In the trailer for Back 4 Blood, the cinematic scene before showing a group of survivors taking on waves of zombies showed hints of the origin of the infection that caused the undead in the game.

In one of the following scenes, one of the infected is shown with the same parasitic worm slithering between its eyes, but what are they?
The Infected In Back 4 Blood Are Known As “Ridden”
As confirmed by the official Back 4 Blood Twitter account, the names of the zombies in Back 4 Blood are “Ridden.”
Hopefully, we’ll get to know more about the ridden in Back 4 Blood’s campaign mode.
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