In their bare-bones tent in southern Gaza, Mostafa Shaaban built his family’s makeshift toilet behind a curtain in a corner. He dug a shallow pit in the sandy soil, poured a concrete slab around it, fixed a bottomless bucket over the hole, then topped it off with a battered, plastic toilet seat. It reeks with a foul odour and buzzes with flies and mosquitoes only a few feet from where they sleep and prepare meals.