After the floods, a wave of disease plagues Pakistanbr br Aamir Hussain surveys the fetid floodwaters hemming his family's makeshift rooftop home in southern Pakistan.Four months after the start of record monsoon rains linked to climate change, the standing water has curdled into a pestilent soup breeding malaria, cholera and dengue.br br The UN has warned of a "second wave" of catastrophe, with the risk that deaths from water-borne disease and malnutrition will outstrip the 1,700 drowned and electrocuted in the initial cascade.