Almost 2 billion people were affected by natural disasters in the last decade of the 20th century, with floods and droughts accounting for 86 per cent of them, the Geneva-based United Nations agency said, calling for a series of measures in response to the resulting health effects.”The most vulnerable victims are the poor and the marginalized, most of whom live in low-quality housing in flood-prone or drought-prone regions,” said Jamie Bartram, Coordinator of WHO’s Water, Sanitation and Health Programme. “In periods of drought, their desperate search for water leads them to drink contaminated water and fail to exercise personal hygiene. And those fleeing floods often drink unclean water too.”Floods are the second most frequent cause of natural disaster after windstorms, but affect more regions and more people than any other phenomenon, WHO said. Drought is the largest cause of death because it often leads to famine.As statistical studies show floods becoming more frequent, WHO called for more efforts to be put into better preparedness and better prevention measures, especially in the least developed countries.Simple, practical measures such as teaching people how to conserve water and keep it safe from contamination and how to store emergency supplies of safe drinking water would help at-risk communities, WHO said. Chlorination is known to reduce diarrhoea, cholera and other diseases.The agency also said that early warning systems to detect rises in mosquito-borne and diarrhoeal diseases and to evaluate the risk of floods and drought also should be set up. Furthermore, sanitation in many regions should be improved because countries with a good infrastructure for drainage and disposal of human waste have far fewer direct health problems during water-related disasters.