Red Echo Syndrome

The first time it happens, most people mistake it for adrenaline. The pulse quickens, the face flushes, and there is a sudden burst of energy that drives the body forward with a clarity that feels earned. It is not until the heartbeat starts echoing that the afflicted realizes something else is doing the driving.
  Red Echo Syndrome is a neurological and hematological disease that hijacks the Infection's connection to the circulatory and auditory systems. The Infection overproduces bioelectrical activity in the blood, flooding the body with heightened oxygen flow and accelerated reflex speed. Strength increases. Reaction time sharpens. For a brief, brilliant window, the afflicted becomes faster and more dangerous than they have any right to be. The cost is stability, sanity, and eventually everything.
  The disease spreads through direct blood contact with infected Raiders or Zombies, or through deliberate injection and transfusion of contaminated blood. Criminal chemists and underground laboratories use it for exactly what it sounds like: creating short-lived weapons out of living people. Rumors persist that Red Echo Syndrome was engineered by Murder Inc. as a weaponized combat enhancer, something designed to turn a person into a killing machine before burning them out. Whether that origin story is true or convenient mythology, the disease is now carried naturally by certain Raiders and Zombies whose Infection strains were permanently altered by exposure to old-world bioweapon residues.
  The syndrome lies dormant until triggered by increased heart rate or an adrenaline spike, typically during combat or a fear response. Once activated, symptoms emerge fast. An elevated pulse, facial flushing, a metallic taste coating the tongue. Bursts of physical energy arrive with an artificial sense of clarity that feels like confidence but is not. Within hours, faint rhythmic sounds begin matching the heartbeat, audible only to the afflicted. Nosebleeds and tremors follow as blood vessels dilate. Then comes the euphoria: manic, electric, and deeply untrustworthy.
  As the condition worsens, the rhythmic sounds resolve into something worse. Auditory hallucinations that mirror the voices of familiar people, urging reckless action, violent impulse, forward momentum with no retreat. The body becomes oversaturated with oxygen and Infection activity. Muscle twitching, facial spasms, severe headaches. The blood itself changes, thickening and darkening to a deep crimson that pulses visibly beneath the skin.
  In advanced stages, the afflicted cycles between hysterical laughter and explosive aggression with little warning or control. The heart begins to misfire, producing moments of staggering pain followed by bursts of unstoppable motion. Each use of the combat abilities the disease enhances pushes the syndrome forward; the very benefits it provides are the mechanism of its advancement. No known mechanic can halt or delay the progression. The Grand Design itself cannot stop it.
  Death at the terminal stage is fast: fifteen minutes after reaching the final stage, the heart gives out. But unlike most wasteland diseases, death here is a full cure. The afflicted returns from the Mortis free of Red Echo Syndrome entirely, the Infection having burned through the contaminated blood during the reset. Survivors retain mild auditory distortion and an aversion to silence. They report that the quiet never feels truly empty anymore, as though the echoes left a mark that the Mortis could not quite erase.
  Treatment before the terminal stage focuses on blood replacement: transfusions at early stages, surgical nerve repair and cardiac intervention at higher stages. The window is narrow. Every moment in combat accelerates the disease, and the disease makes combat feel irresistible. That is the trap of Red Echo Syndrome: it gives you exactly what you need to survive the fight, and the price is that the fight is what kills you.