Why do we keep getting colds or flu every year? Why can't our amazing divinely-designed bodies overcome this virus? Is it just that the cold virus is better at mutating than our white blood cells are at detecting it, or maybe (pure conjecture here) it's a process we need to go through.
The timing couldn't be worse. It's usually the first week of December, the busiest week of the school social calendar, everything needs to be finished by Christmas, and there's all this extra stuff to do. Maybe that's what gave Aldiss the idea.