The city of Uvira, in eastern Democratic Republic of Congo (DRC), has been identified as a cholera transmission hotspot. To stem the spread of the disease, the "Water Against Cholera in Uvira" project was launched in 2015 to improve water supply services. In late January, a workshop was held in Kinshasa, capital of the DRC, to assess the impact of water supply infrastructure improvements on cholera and other diarrheal diseases in Uvira.
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).
The structural improvement program
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):
- Limited production capacity during the April 2020 floods
- Lack of improved power supply (resulting in intermittent service)
- Implementation challenges that prevented the new reservoir from being commissioned at full capacity
- 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).
Overview of the study conducted
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 (1).
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 of approximately 14% in the incidence of diarrheal disease was observed for an increase of 5 units in the water supply quality indicator[1]. Similarly, a 16% decrease in confirmed cholera cases was also observed for the same increase in water service quality[2].
Among all components of the service quality index, the strongest association was observed between continuity and confirmed cholera cases, with an estimated 25% reduction for a 5% increase in monthly pump operating time[3]. The effect was similar for the incidence of diarrheal disease[4]. A statistically significant association was also observed between the amount of water available and the incidence of confirmed cholera cases[5]. 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 (2).
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[1] Incidence rate ratio (IRR) 0.86, 95% CI: 0.73-1.01.
[2] Statistically significant, IRR 0.84, 95% CI: 0.73-0.97.
[3] IRR 0.75, 95% CI: 0.69-0.81.
[4] IRR 0.81, 95% CI: 0.77-0.86.
[5] An increase of 5 L/p/day led to a 24% reduction in cholera incidence (IRR 0.76, 95% CI: 0.61-0.94).
Whole-genome sequencing and phylogenetic analyses of V. cholerae in the region
To understand the dynamics of cholera transmission and the evolution of V. cholerae in the region, a study analyzed 96 V. cholerae O1 isolates collected between 2015 and 2020 in DRC (86 clinical isolates) and Tanzania (10 environmental isolates). These isolates were subjected to antibiotic susceptibility testing, whole-genome sequencing, comparative genomics, and phylogenetic analyses within a global collection of 1,366 seventh pandemic V. cholerae O1 genomes, including an additional 130 genomes from DRC (1998-2020) (3).
From 2001 to 2020, cholera outbreaks in eastern DRC were caused exclusively by the T10 sublineage of V. cholerae O1, which was introduced into East Africa from South Asia in the late 1990s. One clade became predominant after acquiring a mutation associated with reduced sensitivity to ciprofloxacin. The emergence of this antibiotic-resistant clade underscores the need for more systematic documentation of antibiotic use, particularly in the response to cholera outbreaks. To improve the effectiveness of interventions, these results also highlight the need for continuous genomic surveillance and coordinated communication between countries in the Lake Tanganyika basin (3).
Spatial and temporal analysis of cholera in Uvira
A 2018 study identified areas of increased cholera risk of at least 200 meters for 5 days immediately following case presentation at a clinic. The risk was highest for those living closest to cases and decreased over time and space (4). To inform appropriate responses during future cholera epidemics, a study was conducted in Uvira to (1) assess the location, timing, and annual prediction of spatiotemporal clusters of cholera cases and (2) estimate the areas at high cholera risk around incident cases in an endemic setting (Gallandat et al., preliminary results) (5).
The preliminary results of the study, based on data from the period 2016-2020, detected 26 clusters with an average radius of 652 meters. Each cluster alarm predicted increased transmission in the following weeks. They also found a high-risk radius of approximately 585 meters (or RR ≥ 2.0) around incident cases within 5 days after these cases reported to a clinic. Furthermore, a high-risk radius (RR ≥ 1.0) up to 1,915 meters demonstrated persistent risk (Gallandat et al., preliminary results). In Uvira, cholera clusters persist and provide information on where intensive transmission occurs during the beginning of an epidemic. These findings may help target early prevention and control efforts to mitigate seasonal epidemics before they spread (5).
REFERENCES
- Bompangue D, Bafambembe J, Saidi J, Gallandat K, Ross I, Hounmanou G, et al. L’évaluation d’impact des améliorations de l’approvisionnement en eau sur le choléra et les maladies diarrhéiques à Uvira: le mercredi 25 janvier 2023 à Kinshasa. Cette étude a été menée par des chercheurs de la London School of Hygiene and Medicine (LSHTM), en collaboration avec le Ministère de la Santé Publique et la REGIDESO, grâce au soutien de l’Agence Française de Développement (AFD), de la fondation Veolia et d’OXFAM. 2023 Jan 25; Kinshasa, DRC.
- Jeandron A, Saidi JM, Kapama A, Burhole M, Birembano F, Vandevelde T, et al. Water Supply Interruptions and Suspected Cholera Incidence: A Time-Series Regression in the Democratic Republic of the Congo. Brocklehurst C, editor. PLOS Medicine. 2015 Oct 27;12(10):e1001893.
- Hounmanou YMG, Njamkepo E, Rauzier J, Gallandat K, Jeandron A, Kamwiziku G, et al. Emergence of a seventh pandemic Vibrio cholerae O1 multidrug-resistant clade in the Lake Tanganyika basin. Emerging Infectious Diseases. 2023;
- Azman AS, Luquero FJ, Salje H, Mbaïbardoum NN, Adalbert N, Ali M, et al. Micro-Hotspots of Risk in Urban Cholera Epidemics. J Infect Dis. 2018 Oct 1;218(7):1164–8.
- Gallandat K, Knee J, Saidi JM, Rumedeka BB, Azman AS, Finger F, et al. Analyse spatio-temporelle du choléra pour informer la riposte en futur: Uvira, RDC, 2016—2020: Résultats préliminaires. Ruwan Ratnayake. 2023 Jan.
Conclusion
These results highlight the importance and challenges of improving water supply infrastructure to control and prevent cholera and other diarrheal diseases. To have an impact on diarrheal diseases, infrastructure improvement programs must ensure high quality execution and implementation, i.e., ensure that interventions improve the services available to the population. The research platform established in Uvira will also enable significant advances in both understanding cholera dynamics in an endemic region and targeted responses to support cholera elimination efforts.