Radiation Rot

You smell them before you see the lesions. Burnt copper and ozone, sharp enough to cut through the usual wasteland stench of sweat and decay. That smell is a warning, and experienced survivors take it seriously. By the time the skin starts sloughing, the damage is already deep.
  Radiation Rot is a degenerative disease caused by extreme and prolonged exposure to radioactive material or creatures that carry radiological contamination in their bodies. The mechanism is a failure of the Infection's protective instincts. Instead of resisting the radiation, the Infection attempts to absorb and neutralize it, a strategy that works for most toxins but fails catastrophically against sustained radiological assault. The absorbed radiation triggers uncontrollable mutation at the cellular level, breaking down tissue and internal organs while the Infection keeps forcing the body to live through the disintegration. Flesh sloughs away in sheets. The host remains conscious. The Infection will not let them stop feeling it.
  The disease cannot spread through casual contact or proximity (unless airborne radioactive particles are present). Contraction requires exposure to severe radiation sources: tainted Critters, contaminated environments, direct handling of radioactive materials, or extended time in radiation-heavy Zones of Mechanics. Scavengers, Grave Divers, and anyone working in reactor ruins without proper shielding carry the highest risk. Retrogrades are the one exception; their unique biological resistance to radiation makes them naturally immune to Radiation Rot entirely.
  Early stages present as nausea, dizziness, and a burning sensation beneath the skin that resembles a bad sunburn. Body temperature rises as the Infection attempts to metabolize the radiation. Within hours, skin reddens and blisters, and in severe cases, the affected areas emit a faint chemical glow. The progression from discomfort to disfigurement is measured in days, not weeks.
  Mid-stage symptoms involve deep tissue breakdown and organ inflammation. Patches of skin begin to peel, and the body leaks thin, black fluid laced with Infection residue. Victims describe the pain as "burning from the bones outward." Muscle weakness, tremors, and hallucinations become common as oxygen levels in the blood drop. The Infection's attempt to manage the crisis makes other diseases more dangerous; any additional illness contracted by someone with Radiation Rot hits harder and progresses faster.
  Advanced cases display widespread necrosis, internal bleeding, and open wounds that refuse to clot. The Infection continues forcing limited regeneration, trapping the victim in a state of slow decomposition that will not resolve on its own. Death comes from organ failure or shock. Survivors of early treatment retain mottled scarring, sensitivity to light, and in many cases a faint radioactive luminescence in the affected tissue: a permanent, faintly glowing reminder of the Infection's failure to protect them from the world it helped ruin.
  Treatment at Stage 1 is deceptively simple: decontamination and radioprotective herbs. Wash the radiation off before it takes hold. Beyond that, intervention escalates through surgical removal of affected tissue, necrotic skin abrasion, and at Stage 4, full body-part replacement in a morgue space via the Living Experiment. Palliative care at any stage requires a blood transfusion from a donor suffering from Grave Bloom Syndrome at an equal or greater severity, an unusual dependency that links these two conditions in treatment as well as in theme. Death before the terminal stage reduces the disease by one stage rather than curing it outright, meaning the afflicted returns from the Mortis still carrying Radiation Rot, just one step less severe.
  Radiation is the invisible killer of the old world that the new world inherited. It does not growl, does not charge, does not announce itself with war cries or the shuffle of dead feet. It simply waits in the soil, the water, the ruins, the bones of creatures that wandered too close. And when the Infection tries to swallow it, both the radiation and the host pay the price.