A deadly threat is lurking in the wake of the tsunami tragedy – one that could double the number of lives the catastrophe claims.Disease is the silent enemy that is poised to spread even more misery, with sewage-contaminated water the main risk factor. Amid fears of cholera, malaria and dengue fever, aid organisations are scrambling to get clean drinking water to affected areas. The whole relief operation has become a desperate race against time. Tonnes of water purification tables are being shipped to the disaster zones. But in Sri Lanka and elsewhere, cases of diarrhoea and vomiting are being reported – indicating that water contamination is already taking its toll.