OBJECTIVES

Cholera is an easily treatable disease, but many people are still unnecessarily dying from it. To improve current case management practices and prevent mortality requires a comprehensive understanding of who is at higher risk of dying. To identify the most common risk factors, a scoping review was undertaken, to explore the literature and summarise the evidence on cholera mortality and reported risk factors.

METHODS

Following the scoping review framework proposed by Arksey and O'Malley (2005), Pubmed, EMBASE, Web of Science, LILACS, Scielo, Cochrane and Open Grey and African Journals Online were searched on 24 November 2021, without restrictions in language or date. After screening and assessing the records across predefined criteria, we performed a thematic analysis on mortality.

RESULTS

A total of 77 studies were included in the final review. The potential reasons explaining the observed mortality were classified in the following categories: Patient characteristics; Healthcare; and Health‐seeking behaviour. The identified risk factors were multi‐dimensional, inter‐dependent and context‐specific. When exploring the patients' characteristics, the available data suggested that in many contexts, case fatality ratios were higher among males and older people, especially those aged 50 or above. Twelve studies reported the place of death, with the percentage of community deaths ranging from 23% to 96%. Evidence on comorbidities and cholera deaths was too scarce for analysis.

CONCLUSIONS

Cholera has been a disease of global importance for more than two centuries. Despite this, our review highlighted that there has been limited published evidence about factors that increase the risk of cholera‐related death. Collecting, reporting and analysing baseline characteristics such as age, sex and predisposing conditions can improve our understanding of cholera mortality risk factors and guide improvements in future case management recommendations.

Cholera is a bacterial water-borne diarrheal disease transmitted via the fecal-oral route that causes high morbidity in sub-Saharan Africa and Asia. It is preventable with vaccination, and Water, Sanitation, and Hygiene (WASH) improvements. However, the impact of vaccination in endemic settings remains unclear. Cholera is endemic in the city of Kalemie, on the shore of Lake Tanganyika, in the Democratic Republic of Congo, where both seasonal mobility and the lake, a potential environmental reservoir, may promote transmission. Kalemie received a vaccination campaign and WASH improvements in 2013–2016. We assessed the impact of this intervention to inform future control strategies in endemic settings. We fit compartmental models considering seasonal mobility and environmentally-based transmission. We estimated the number of cases the intervention avoided, and the relative contributions of the elements promoting local cholera transmission. We estimated the intervention avoided 5,259 cases (95% credible interval: 1,576.6–11,337.8) over 118 weeks. Transmission did not rely on seasonal mobility and was primarily environmentally-driven. Removing environmental exposure or contamination could control local transmission. Repeated environmental exposure could maintain high population immunity and decrease the impact of vaccination in similar endemic areas. Addressing environmental exposure and contamination should be the primary target of interventions in such settings.

BACKGROUND

In 2019–2020, preventative Oral Cholera Vaccine campaigns were conducted in 24/32 non-contiguous health areas of Goma, DR Congo. In August 2022, we measured coverage and factors potentially influencing success of the delivery strategy.

METHODS

We used random geo-sampled stratified cluster survey to estimate OCV coverage and assess population movement, diarrhea history, and reasons for non-vaccination.

RESULTS

603 households were visited. Coverage with at least one dose was 46.4 % (95 %CI: 41.8–51.0), and 50.1 % (95 %CI: 45.4–54.8) in areas targeted by vaccination compared to 26.3 % (95 %CI: 19.2–34.9) in non-targeted areas. Additionally, 7.0 % of participants reported moving from outside Goma since 2019, and 5.4 % reported history of severe diarrhea. Absence and unawareness were the main reasons for non-vaccination.

CONCLUSION

Results suggest that targeting non-contiguous urban areas had a coverage-diluting effect. Targeting entire geographically contiguous areas, adapted distribution, and regular catch-up campaigns are operational recommendations to reach higher coverages arising from the study.

We evaluated the spatiotemporal clustering of rapid diagnostic test−positive cholera cases in Uvira, eastern Democratic Republic of the Congo. We detected spatiotemporal clusters that consistently overlapped with major rivers, and we outlined the extent of zones of increased risk that are compatible with the radii currently used for targeted interventions.