When the V-ACT process occurs, the heart begins pumping at an alarming rate, causing noticeable blood seepage in the skin and giving it a crimson shade of red. The subject's fingers and toes develop sharp claws and an increased muscle mass and movement speed. The subject's level of aggression also increases greatly from that of the typical zombie. When zombies mutate into Crimson Heads, virtually nothing will stop them from pursuing their prey, making these creatures extremely dangerous.
While not known why, their bodies also emit steam or dust. It's possible that their body temperature may rise along with the fastly paced pumping blood, producing the steam from the intense heat emitting off of their bodies.