The Laughing Blight

The first giggle catches you off guard. Nervous, sharp, and badly timed; a laugh during a moment of silence when someone is dying. You try to swallow it. It comes back louder.
  The Laughing Blight is a mutated strain of Bad Brain Syndrome, reshaped through generations of exposure to Raider Infection and stress-based psionic feedback. Where Bad Brain tears the mind apart through rage and degeneration, the Laughing Blight burns it away through hysteria. Victims lose the ability to regulate emotional response entirely, erupting into fits of uncontrollable laughter during moments of stress, fear, tension, or grief. The laughter is never joyous. It is forced, jagged, and painful, a nervous breakdown that echoes and never ends. The condition compromises stealth, composure, and ultimately survival, often marking its victims for death long before the final stage arrives.
  Transmission occurs through direct exposure to Raider-contaminated blood, saliva, or airborne Infection released during violent encounters. Unlike standard Bad Brain, the Laughing Blight can be contracted from lingering Raider corpses or from the eruption that occurs when a Raider is put down. Raiders carrying the disease give dark laughs on the field, turning their battlefield presence into something newly threatening. Tainted Lineage are prime carriers; their Infection sustains the mutated strain longer than others, and they begin the disease at an advanced stage.
  The progression unfolds over months, advancing at the end of each attended game or the first time the carrier enters Bleed Out during an event. Early stages bring nervous laughter and uncontrollable giggling during stressful moments. Fear, Agony, and Attract effects hit harder. As the disease deepens, the grinning and snickering become constant. Stealth becomes impossible without burning Resolve. By the moderate stage, hysterical fits of laughter trail off into muscle spasms and coughing; the lines between humor, fear, anger, and sadness dissolve entirely. The afflicted cannot resist reacting to violence, cannot stop themselves from performing a Killing Blow on a fallen target (friend or foe) without conscious effort. In the severe stage, communication breaks down to stuttered words between outbursts of alternating laughter and sobbing.
  Treatment ranges from blood transfusion at early stages to surgical removal of damaged brain tissue and, in advanced cases, trepanation and morgue-space brain replacement. Death reduces the disease by one stage rather than curing it, making the Laughing Blight notably persistent. Those who die at Stage 5 return from the Mortis still carrying the disease at Stage 2, unable to simply reset through the usual cycle of death and return.
  Post-mortem analysis reveals the same neural scarring as Bad Brain Syndrome, with one distinguishing feature: distinct fissures in the facial muscles from prolonged, involuntary smiling. A grim reflection of what passes for humor in the wasteland, frozen in place long after the laughter has stopped.