What is Cholera and why does it matter?
Cholera is a diarrhoeal disease caused by the bacteria Vibrio cholerae. The infection if untreated can within hours, cause diarrhoea and vomiting leading to severe dehydration and in some cases death. Cholera is easily treated with oral rehydration solution so why then are there still so many cases reported every year? In fact the World Health Organisation (WHO) estimates that there are between 3-5 million cholera cases and 100,000 deaths every year, of which only a fraction are officially reported.
The battle against cholera has been fought since it was first reported in Asia in 1817. The work of Dr. John Snow during the outbreaks in London’s Soho district in the 1850’s focussed attention to its water-borne transmission route and highlighted the need for improved water supply, sanitation and hygiene (WASH) infrastructure, which we enjoy today. These days, cholera outbreaks are more likely to occur following emergencies, particularly in those countries where WASH services have been damaged or still remain an unmet need. Cholera knows no boundaries. It is spread by multiple pathways, mainly through ingestion of contaminated water and food and can decimate an unprepared population such as was seen in Haiti following the earthquake in 2010.
The Environmental Health Group strives to continue John Snow’s work to find evidence-based practical solutions to control and prevent this devastating disease.
Key research and contributions to this area:
Systematic literature review of WASH activities to prevent Cholera
This systematic literature review conducted by Sandy Cairncross, Jeroen Ensink and Tanya Kahawita evaluated the impact of WASH activities undertaken to prevent and control cholera outbreaks in Guinea-Conakry and Guinea-Bissau. The evaluation had three aims: 1) To assess whether the WASH interventions have resulted in an improved understanding of the risk factors and mode of transmission of cholera among the target population, policy makers and those involved in the implementation of the cholera control activities, 2) To assess whether the WASH interventions have resulted in an improvement in water quality, sanitation and hygiene in those households and neighbourhoods affected by the cholera epidemic and 3) To provide recommendations, based on the findings of the field evaluation and a literature review, for the improvement of the current cholera control program.
Current research in this area:
Aurelie Jeandron is currently working on an impact evaluation of a large water supply improvement project in Uvira, in Eastern DRC. Funded by the French Development Agency, the European Union, the Veolia Environment Foundation and OXFAM UK, this project aims at improving access and reliability of tap water supply in a cholera endemic area on the shores of Lake Tanganyika.
Uvira is located in South-Kivu province in Eastern DRC, at the border with Burundi, and has an estimated population of 230,000 inhabitants (2015). Cholera is endemic in Uvira and has been identified as one of eight ‘cholera hotspots’ in DRC with a high annual incidence of 632 cholera admissions per 100,000 inhabitants.
Access to safe drinking water is generally low with almost half of all households using surface water source that is rarely boiled or chlorinated at home. Some are served by the existing the Regideso water supply system, which provides chlorinated water, but this limited network (2800 private and shared taps) experiences frequent service interruptions. Households spend an average of one hour a day collecting water, with 75% of water collection done by women and girls. Only a third of households are estimated to have an improved sanitation facility.
Between 2017 and 2019, the water supply system in Uvira will benefit from a €10 million improvement project funded by the French Development Agency (AFD), the Veolia Foundation and the European Union, that will increase Regideso water treatment capacity, strengthen the water distribution network, set-up 110 community-managed public taps and double the number of functional water taps across town.
Although it has long been argued that improving domestic water supply is critical in reducing faecal-oral transmission of enteric pathogens by making greater quantities of water available for hygienic practices, there have been no rigorous controlled intervention studies. Specifically with regard to cholera, it is unclear if and how improving water supply – i.e. the quantity of water available for domestic consumption – might prevent and control outbreaks in endemic settings.
AFD and the Veolia Foundation contracted the London School of Hygiene and Tropical Medicine in 2014 to design and conduct an impact evaluation of the water supply improvement works on cholera, other diarrhoeal diseases and water-related practices. A stepped wedge cluster randomised controlled trial (SWcRCT) will be carried out to measure the effect of the intervention on cholera centre admission and confirmed cholera cases (www.clinicaltrials.gov identifier: NCT02928341). In parallel, a cohort study will be implemented to assess how water-related practices change following the intervention.
Based on data collected daily since 2009 at the Uvira Cholera Treatment Centre (CTC) and at the water treatment plant, we first conducted a time-series regression between suspected cholera and daily amounts of tap water supplied across town and found a strong and consistent association between interruptions in water service and suspected cholera. Spatio-temporal modelling of admissions at Uvira CTC since 2009 is currently being used to explore the relationship between neighbourhoods’ water and sanitation characteristics and local patterns of suspected cholera incidence.
Since 2009, more than 10’000 cases were admitted to the Cholera Treatment Centre in Uvira. The CTC admits all patients presenting with severe acute diarrhoea. Patients are treated for dehydration and administered broad spectrum antibiotics and/or zinc. However, in the absence of adequate local laboratory facilities, regular confirmation of cholera is not conducted, except occasionally at the beginning of suspected cholera outbreaks. Admission to, and treatment at, the CTC is free of charge for all patients. In order to confirm or infirm cholera diagnosis amongst patients admitted to the CTC, we started a cholera confirmation study in April 2016, with rapid diagnostic tests.
The impact evaluation will last until summer 2020.
Systematic literature review of the health impact of WASH interventions in cholera outbreak response.
This systematic literature review will review the existing evidence to distil which WASH related activities can be considered best practice during cholera outbreaks.
Publications related to Cholera:
- Jeandron A, Saidi JM, Kapama A, Burhole M, Birembano F, Vandevelde T, et al. (2015) Water Supply Interruptions and Suspected Cholera Incidence: A Time-Series Regression in the Democratic Republic of the Congo. PLoS Med 12(10): e1001893. https://doi.org/10.1371/journal.pmed.1001893
- Cairncross, S., Ensink, J., Kahawita T. Evaluation of the WASH activities undertaken to prevent and control cholera outbreaks in Guinea-Conakry & Guinea-Bissau & systematic literature review. In HUmanitarianResponse. 2009.
- Taylor DL, Kahawita TM, Cairncross S, Ensink JHJ. The Impact of Water, Sanitation and Hygiene Interventions to Control Cholera: A Systematic Review. PLoS ONE. 2015;10(8):e0135676.