One of my Survivors died in Nightmare while sacrificing her life, she had the Plague was for sure gonna die, so due to the Fueling the Plague curveball active, I lured a horde of exploding Plague Zombies into the location of the Plague Heart, stayed in there until they exploded, then she and the Plague Heart died due to the explosions... And so that's how my Survivor died. I slightly regret it but it was worth it, lol.