Gut Hatch Fever

The first sign is a feeling of fullness that has nothing to do with food. A tightness below the ribs, a warmth that sits deeper than digestion, a sense that something has settled in and made itself at home. Most survivors dismiss it as bad rations or a rough night. They are wrong.
  Gut Hatch Fever is a parasitic disease that begins when eggs from a wasteland creature are implanted into the soft tissue of a living host. The responsible organisms vary by region: burrowing insects in the dust flats, fungal worms along the river deltas, spore-feeding crustaceans in the coastal ruins. The method of delivery differs, but the result is the same. The Infection inside the body reacts to the eggs as though they belong there, mistaking them for regenerative tissue. It bonds with them, feeds them energy, keeps them warm and protected. The host's own biology becomes an incubator, and the body cannot tell the difference between healing itself and nurturing something that will eventually tear its way out.
  Transmission requires direct implantation. Gut Hatch Fever cannot spread through proximity, shared air, or casual touch. The eggs must be deposited into living flesh by the parasitic creature itself, or through contact with ruptured eggs from an infected corpse. Scavengers who handle the remains of the afflicted without proper protection risk exposure; the reactive fluid from burst eggs burns through skin and carries the infection with it. Once inside, the eggs require the warmth and Infection of a living body to mature. They cannot survive outside a host for more than a few hours.
  Early symptoms present as mild stomach pain, nausea, and episodes of fullness unrelated to eating. Within weeks, the afflicted experience internal warmth and a faint sense of movement that worsens after meals or physical exertion, the eggs responding to the host's increased metabolism. By mid-stage, the abdomen swells visibly. Pressure discomfort and intermittent muscle spasms become constant companions. Some hosts hear or feel rhythmic pulses that resemble breathing from within. The body begins producing a black, tar-like residue, expelled around the navel or through vomit, as the Infection struggles to manage the growing parasites.
  Advanced cases are difficult to witness. Severe cramping, internal tearing, audible chittering or scraping from inside the abdomen. The eggs feed directly on internal tissue and Infection stores, draining the host toward exhaustion, fever, and delirium. The final stage ends the only way biology allows: abdominal rupture. The larvae emerge, leaving behind a partially hollowed cavity and catastrophic tissue loss. Survivors of earlier surgical intervention carry deep scarring, chronic digestive problems, and an understandable distrust of anything that buzzes, burrows, or hums in the dark.
  Treatment depends entirely on timing. Early-stage intervention with a mildly toxic brew can kill the eggs before they develop. Surgical removal becomes necessary as the eggs grow, requiring progressively more skilled physicians and more invasive procedures. By the time the larvae are nearly mature, the only option is administering poison strong enough to kill them inside the host, with the afflicted suffering the full effects. At terminal stage, any medical intervention triggers immediate hatching. Death before that point remains the reliable, if brutal, alternative.
  The disease is slow. It advances over months, not hours. That pace is part of what makes it so insidious: there is always time to seek treatment, always a reason to wait just a little longer. And for some, that waiting becomes the thing that kills them.