Over the course of a couple of days, all the liquid is lost from the body, leaving in its wake a dried shell. Just a slight vibration is enough for the corpse to detonate, sending millions of dust spores into the air.
Everyone over the age of 40 has been wiped out by an unidentified fungal plague. Only the young remain. The survivors leave their shelters and emerge into a world blanketed with clouds of drifting spores. They believe that the worst is over, now is the time to start re-building. They have yet to encounter the abominations, altered by the spores. They thought the plague was the end.
The plague is just the beginning.