Evaluation of the impact of water supply improvements on cholera and diarrheal diseases in Uvira, DRC

Cholera remains a major health issue worldwide, affecting populations with limited access to safe drinking water and sanitation facilities. The Democratic Republic of Congo (DRC) is one of the most affected countries, with the majority of cases concentrated in the east of the country, in the Great Lakes Region. The town of Uvira, in South Kivu Province, has been identified as a hotspot for cholera transmission.

The city of Uvira has 280,000 inhabitants and stretches along the shores of Lake Tanganyika. The drinking water supply network of Uvira dates from the colonial era and was severely damaged during the First Congo War (1996-97). Before 2018, the network coverage estimates varied between 10% and 31% of the population. Furthermore, the humanitarian situation in Uvira is unstable as persistent conflicts in the region have caused insecurity and population movement (1).

The Global Task Force on Cholera Control (GTFCC), initiated by WHO, has set a goal of eliminating cholera by 2030 by focusing on three main areas, including targeted prevention measures to improve access to water, sanitation and hygiene services in cholera hotspots. Therefore, to improve water supply services in Uvira, the "Water against Cholera in Uvira" project was launched in 2015 and has been focused on the following activities (1):

• Construction of a new reservoir (2,000 m3)
• Rehabilitation of the Mulongwe treatment and pumping station to increase capacity
• Rehabilitation (10 km) and extension of the network pipes (24 km)
• Installation (or rehabilitation, depending on the situation) of private connections (2,368 completed, 2,997 planned) and construction of new standpipes (93 completed, 115 planned)

The project was managed by Regideso and financed by the French Development Agency, the Veolia Foundation, the European Union and Oxfam GB, with a total investment of over 15 million euros (1).

Significant investments have been made to improve the water supply, production and distribution infrastructure in Uvira. This has resulted in a significant increase in access to water between 2019 and 2021. However, the quantity of water available and service continuity have remained satisfactory. The gaps between infrastructure improvements and water supply quality were due to several difficulties (1):

1. Limited production capacity during the April 2020 floods
2. Lack of improved power supply (resulting in intermittent service)
3. Implementation challenges that prevented the new reservoir from being commissioned at full capacity
4. Sub-optimal system operation by staff

These results highlight the need for cross-sectoral coordination (water, electricity, land use) to implement such complex infrastructure projects. They also highlight the need for sufficient and qualified human resources to ensure adequate operation of the infrastructure (1).

To measure the progress in Uvira, an indicator was defined to characterize the quality of the water supply service. The indicator was based on water accessibility, availability, continuity and affordability, which were analyzed between January 2017 and December 2021. These four parameters were then integrated to establish a single indicator to describe the evolution of the quality of the water supply service over time, which could be integrated into subsequent epidemiological analyses (2).

Rigorous studies of the impact of improved water supply on endemic cholera transmission in low-income urban settings are lacking. To address this research gap, researchers from the London School of Hygiene and Medicine (LSHTM) have taken up this issue in collaboration with the Ministry of Public Health and Regideso, with the support of AFD, the Veolia Foundation and Oxfam (1).

A clinical surveillance system was established by the LSHTM based at the cholera treatment center (CTC) at Uvira General Hospital and the cholera treatment unit (CTU) at Kalundu Health Center (since 2019). Cases of diarrhea or cholera admitted to these health facilities were systematically recorded and mapped to 16 clusters. An epidemiological analysis was conducted from January 2017 to December 2021 on all patients with diarrheal diseases presenting at one of the two referral centers. A total of 4,556 cases of diarrheal disease were treated in Uvira during this period, with a cholera confirmation rate of 45.4% (1).

It appears that infrastructure improvements alone did not have a significant effect on the incidence of diarrheal disease or cholera. However, the quality of the water supply service available to the population was fundamental to reduce the burden of diarrheal disease and cholera. A decrease in the incidence of diarrhoeal diseases and confirmed cases of cholera was observed in connection with the improved quality of the water supply service (1).

Among all components of the service quality index, the strongest association was observed between continuity and confirmed cholera cases. A statistically significant association was also observed between the amount of water available and the incidence of confirmed cholera cases. By contrast, no statistically significant association was observed with accessibility alone or with the affordability parameter (1).

Overall, these results confirm that improving water supply service can help to reduce the incidence of these diseases (1). These findings also correlate with a previous LSHTM study showing a clear association between reduced tap water availability and increased cholera incidence in Uvira (1).
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