Cholera risk from unreliable tap water supply

Interruptions in continuous piped water supply may lead to an increased number of cholera and other severe diarrhoea cases in urban areas of the Democratic Republic of Congo, according to new research published in PLOS Medicine.

The findings from a study conducted in the city of Uvira, on the shores of Lake Tanganyika, suggest cholera control strategies should include providing reliable, continuous tap water supplies in endemic areas.

Research led by the London School of Hygiene & Tropical Medicine found a significant association between piped water interruptions, often due to electricity cuts or equipment breakdown, and admissions to a cholera treatment centre in Uvira . Suspected cholera admissions increased by 155% in the 12 days following a day without tap water supply, compared to when supply was at its maximum capacity.

The Democratic Republic of Congo has high levels of cholera, reporting 33,661 cases of cholera in 2012, and 819 cholera-related deaths - 27% of global deaths due to the disease. Cholera is an infectious disease that is spread by water or food infected with the bacterium Vibrio cholerae. Supplying clean water is crucial in preventing cholera transmission; however, investing in water supply is expensive, and it is still uncertain what minimum level of access to water is necessary to prevent cholera.

Around half of the population in the Democratic Republic of Congo currently have access to improved water sources (piped supply, protected wells and boreholes), with only 8% specifically having have access to piped water on their premises. The situation in Uvira is better than those national figures, as it is estimated that 25% of the households have access to piped water in their house or in their courtyard, with 80% of the population using tap water regularly or occasionally.

Lead author Aurélie Jeandron, Research Fellow at the School, said: "Our results show for the first time that interruptions in piped water can lead to increased cases of cholera in urban areas, even where piped water is not widely accessible to the population. It is not enough to improve water sources by putting in a piped supply - we must ensure that water is supplied regularly and in a sufficient quantity."

During a five-year study period, 5,745 patients over the age of five were admitted to the Uvira cholera treatment centre with suspected cholera. 23% of these cases were attributable to interrupted water supply. The study suggests that neighbourhoods which relied more heavily on tap water were more vulnerable, with 31% of suspected cholera cases from these areas attributed to interrupted water supply.

Unreliable piped water supply may lead to an increase in cases of cholera because people revert to using other water sources which are unsafe, or cut down on washing their hands or food thereby increasing the risk of exposure to the cholera bacteria. Some people anticipating interruptions in their piped water supply may store extra in their homes, increasing the risk of contamination during collection and storage. Additionally, interruptions and low pressure in a continuous piped water supply may allow cholera bacteria to enter the system.

Co-author Dr Jeroen Ensink, Senior Lecturer in Public Health Engineering at the School, said: "This study shows that we cannot just assume that a piped water supply is a safe water source, because when it does not provide water, people revert back to unsafe sources and unhygienic practices.  Education about behaviour remains important, as does water chlorination, but this clear link between water supply interruptions and cholera risk shows how significant water availability and reliability is for the control of cholera and other diarrhoeal diseases."

This study was funded by Agence Française de Développement and the UK Medical Research Council. The authors note that a limitation of the study was that laboratory analysis was not available to confirm that all the patients admitted to the cholera treatment centre with symptoms of watery diarrhea were infected with cholera, although cholera was confirmed present in the area.


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