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New study supports action to tackle poor sanitation in developing countries

November 09, 2007

Improvements in sanitation and sewerage systems can have a dramatic effect on reducing cholera and other diarrhoeal diseases, research has shown. The study, co-funded by the Wellcome Trust, has led scientists to call for action to improve urban sanitation as an effective way of improving health in developing countries.

According to the WHO, the number of cholera cases during 2006 was 236,896, with 6,311 deaths in 52 countries, a rise of 79% on the previous year. The importance of sanitation in preventing cholera and other diarrhoeal diseases was recognised in the Millennium Development Goals, which set a target of halving the number of people without access to basic sanitation by 2015. However, this target is unlikely to be achieved because the resources allocated to it are small. Part of the reason for this neglect of sanitation is the absence of rigorous evidence for its effectiveness in prevention of disease.

Now, in research published today in the journal The Lancet, Professor Mauricio Barreto and colleagues from the Federal University of Bahia, Salvador, Brazil, have shown that urban sanitation is a highly effective health measure.

In 1997, the city of Salvador in Brazil implemented a city-wide sanitation project, known as Bahia Azul, or Blue Bay. Its objective was to increase the number of households with an adequate sewer system from 26% to 80%, including extending the sewerage network, improving water supply and capacity-building in ten smaller towns in the state.

Professor Barreto and colleagues studied the health impact of the sanitation programme in reducing cases of diarrhoea in children under the age of three years old, working with two cohorts of around 1,000 children. Previous studies had evaluated sanitation only in small scale interventions, i.e latrines in village.

The researchers found that overall prevalence of diarrhoea fell by 22%. However, in high-risk areas, where sanitary conditions were poorest, overall prevalence fell by double this amount, down 43%, despite lower than average requests by households for sewer connections.

"These results show clearly that city-wide sanitation is effective at combating diarrhoea and related diseases," says Professor Barreto. "Importantly, they show that it has the biggest effect in the poorest areas, where sanitation - and hence, disease - is worst. Sanitation can be seen as being an equitable approach to tackling a major health problem."

In order to ensure that sanitation programmes are implemented, Professor Barreto believes that more needs to be done by international organisations and central government.

"It's usually up to the consumer to pay for sanitation, installing flush toilets, septic tanks and so on," he says. "However, there are limits to what can be achieved by individual households alone, especially when what is needed is not household toilets, which are already common, but sewers.

"At a typical cost of US$160 per person, cash-strapped municipalities cannot afford to invest in sewerage systems. International aid agencies and central government must take action to help tackle this serious health problem."

The research comes ahead of International Year of Sanitation 2008, which will be launched at the United Nations Headquarters on 21 November 2007.

Wellcome Trust