Picture the following sacred but unhygienic scene: Pilgrims from a dozen countries converge on one small city. They stay in cramped hotels, using communal toilets and eating meals together. For their main ritual, they converge on the tomb of a woman, the sister of a holy man, and as they get closer, they feel with rising intensity grief over her death and the deaths of her kin. The grief is a commandment: Each tear, according to one tradition, will be transformed in the afterlife into a pearl, and an angel will compensate them for their tears with a bucket of pearls that will be signs of their devotion when they arrive at the gate of paradise. But for now the bodily fluids are flowing, wiped away occasionally by bare hands, and the crowd is getting denser. A metal cage surrounds the tomb itself, and when the weeping pilgrims reach it, they interlace their fingers with its bars, and many press their face against it, fogging up the shiny metal with their breath. Some linger for minutes, some for seconds. In a single day, many thousands pass through the same cramped space—breathing the same air, touching the same surfaces, trading new and exotic diseases.
