in more than million bottles of sws product enough to treat billion litres of drinking water and supply million users were sold for routine nonemergency nonoutbreak use in countries nearly percent of these sales were in just three countries zambia madagascar and malawi which means that these countries have achieved scale in terms of coverage for household water treatment and safe storage in a series of published randomised intervention trials conducted by cdc in three continents the safe water systems have shown to reduce the diarrheal disease incidence by with an average of whereas unsafe or insufficient water affects primarily the individuals concerned inadequate sanitation can have significant external effects through the spread of epidemics