In 2007, more than 7.6 million bottles of SWS product - enough to treat 7.8 billion litres of drinking water and supply 10.6 million users - were sold for routine (non-emergency, non-outbreak) use in 20 countries. Nearly 60 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 25-84%, with an average of 50%. Whereas unsafe or insufficient water affects primarily the individuals concerned, inadequate sanitation can have significant external effects through the spread of epidemics.