Identifying and quantifying the factors associated with cholera-related death during the 2018 outbreak in Nigeria

Trends of cholera epidemics and associated mortality factors in Cameroon: 2018-2023: a cross-sectional study

BACKGROUND

Cameroon has faced frequent and severe cholera outbreaks since 1971, with case-fatality rates (CFRs) ranging from 12% in 1991, to 5.3% in 2014, all higher than the less than 1% cholera CFR target set by WHO. However, not many studies providing insight on context-specific risk factors have been published. The purpose of this study was to describe the recent cholera outbreaks in Cameroon and to determine factors associated with mortality.

METHODS

This was an analytical cross-sectional study that employed a retrospective design exploiting Ministry of Public Health cholera line-lists from 2018-2023. These line lists were obtained from the Public Health Emergency Operations Coordination and Control Center, compiled into a single Microsoft Excel Sheet, cleaned and analyzed using Microsoft Excel 2016 and SPSS version 20. Cholera cases were defined as those confirmed in reference laboratories via stool culture and suspected cases with proven epidemiological link to laboratory-confirmed cases (suspected cases in health districts with active laboratory-confirmed cases). Factors associated with cholera mortality were identified using binary logistic regression (adjusted odds ratios), after socio-demographic, clinical, and geographical distribution of cholera cases were described. Maps were generated using QGIS version 3.28.14.

RESULTS

Between May 2018 and March 2023, Cameroon experienced four cholera epidemics resulting in 18,986 reported cases and affecting 8 out of 10 administrative regions. The three coastal regions (Littoral, South and South-West Region) reported 83.4% (15,839/18,986) of all the cases while the remaining five affected regions jointly reported 16.6% (3,147/18,986) cases. The most represented age group were those aged 25-35 years (21.9%; 4,163/1,876) and the male: female sex ratio was 1.27. The overall CFR was 2.7% (478 deaths/17,967 cases with known outcome) and was highest among persons > 65 years (6.8%; 59/869). Urban areas notified more cases than rural areas (13,267 vs 5,484). Factors associated with increased mortality were male sex (aOR 1.61, 95% CI: 1.30-2.04), dry season (aOR 1.67, 95% CI: 1.28-2.22), age above 45 years (aOR 1.79, 95% CI: 1.45-2.22) and severe dehydration at consultation (aOR 12.76, 95% CI: 7.66-21.25).

CONCLUSIONS

Cholera outbreaks occurred in eight out of the ten administrative regions in Cameroon during the study period and mortality appeared to be driven by multiple factors notably severe dehydration at time of consultation, advanced age, male sex and the dry season. The high caseloads and case-fatality rates reiterate the need for further strengthening of existing cholera surveillance and outbreak response mechanisms.

Risk factors for cholera mortality: A scoping review

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 Outbreaks in Low- and Middle-Income Countries in the Last Decade: A Systematic Review and Meta-Analysis

Cholera is linked to penury, making low- and middle-income countries (LMICs) particularly vulnerable to outbreaks. In this systematic review, we analyzed the drivers contributing to these outbreaks, focusing on the epidemiology of cholera in LMICs. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered in PROSPERO (ID: CRD42024591613). We searched PubMed, Scopus, Web of Science, and Google Scholar to include studies on cholera outbreaks that occurred in LMICs from 1 January 2014 to 21 September 2024. Studies on outbreaks outside LMICs and focusing on sporadic cases were excluded. The risk of bias among included studies was assessed using a modified Downes et al. appraisal tool. Thematic analysis was used to synthesize the qualitative data, and meta-analyses to estimate the pooled prevalence. From 1662 records, 95 studies met inclusion criteria, primarily documenting outbreaks in Africa (74%) and Asia (26%). Contaminated water was the main route of disease transmission. The pooled fatality prevalence was 1.3% (95% CI: 1.1-1.6), and the detection rate among suspected cases was 57.8% (95% CI: 49.2-66.4). Vibrio cholerae O1 was the dominant serogroup while Ogawa was the dominant serotype. All studies reporting biotypes indicated El Tor. Although the isolates were 100% susceptible to ofloxacin, levofloxacin, norfloxacin, cefuroxime, and doxycycline, they were also fully resistant to amikacin, sulfamethoxazole, trimethoprim, and furazolidone. The persistence of cholera outbreaks in destitute areas with limited access to clean water and sanitation emphasizes the need for socioeconomic improvements, infrastructure development, and ongoing surveillance to support timely responses and achieve long-term prevention.

Cholera in Nigeria: A review of outbreaks, trends, contributing factors, and public health responses

Cholera remains a significant public health challenge in Nigeria, with recurrent outbreaks exacerbated by inadequate water, sanitation, and hygiene (WASH) infrastructure, as well as conflict and displacement. This review examines cholera outbreaks in Nigeria from 2010 to 2024, analyzing epidemiological trends, contributing factors, and public health responses. Seasonal peaks during periods of heavy rainfall and flooding have consistently facilitated Vibrio cholerae transmission, with Northern regions disproportionately affected due to poor infrastructure and ongoing conflicts. Displacement into overcrowded camps has heightened vulnerability, particularly in conflict-affected areas such as Borno and Adamawa. The outbreaks have exhibited multiple epidemic waves within single periods, reflecting persistent transmission dynamics. Recent outbreaks have seen higher incidence rates among children under the age of five and vulnerable populations, highlighting the need for targeted interventions. Public health responses have focused on improving surveillance, case management, and WASH infrastructure, with coordinated efforts from national and international agencies. Vaccination campaigns, particularly in high-risk areas, have proven effective in controlling outbreaks. However, challenges remain, including inadequate healthcare capacity, vaccine stockouts, and the emergence of antimicrobial-resistant Vibrio cholerae strains (serogroup O1) resistant to antibiotics such as tetracycline, doxycycline, ampicillin, and trimethoprim-sulfamethoxazole, complicating treatment efforts. The COVID-19 pandemic further strained Nigeria's healthcare system, underscoring the need for an integrated health system to be strengthened to manage concurrent public health crises. This review emphasizes the importance of a multi-sectoral approach to cholera prevention and control, addressing underlying social determinants and ensuring sustained investments in public health infrastructure to mitigate future outbreaks.

Development of a Scorecard to Monitor Progress toward National Cholera Elimination: Its Application in Uganda

In 2017, the Global Task Force for Cholera Control (GTFCC) set a goal to eliminate cholera from ≥ 20 countries and to reduce cholera deaths by 90% by 2030. Many countries have included oral cholera vaccine (OCV) in their cholera control plans. We felt that a simple, user-friendly monitoring tool would be useful to guide national progress toward cholera elimination. We reviewed cholera surveillance data of Uganda from 2015 to 2021 by date and district. We defined a district as having eliminated cholera if cholera was not reported in that district for at least 4 years. We prepared maps to show districts with cholera, districts that had eliminated it, and districts that had eliminated it but then "relapsed." These maps were compared with districts where OCV was used and the hotspot map recommended by the GTFCC. Between 2018 and 2021, OCV was administered in 16 districts previously identified as hotspots. In 2018, cholera was reported during at least one of the four previous years from 36 of the 146 districts of Uganda. This number decreased to 18 districts by 2021. Cholera was deemed "eliminated" from four of these 18 districts but then "relapsed." The cholera elimination scorecard effectively demonstrated national progress toward cholera elimination and identified districts where additional resources are needed to achieve elimination by 2030. Identification of the districts that have eliminated cholera and those that have relapsed will assist the national programs to focus on addressing the factors that result in elimination or relapse of cholera.

Healthcare workers knowledge of cholera multi-stranded interventions and its determining factors in North-East Nigeria: planning and policy implications

BACKGROUND

Healthcare workers' (HCWs) knowledge of multi-stranded cholera interventions (including case management, water, sanitation, and hygiene (WASH), surveillance/laboratory methods, coordination, and vaccination) is crucial to the implementation of these interventions in healthcare facilities, especially in conflict-affected settings where cholera burden is particularly high. We aimed to assess Nigerian HCWs' knowledge of cholera interventions and identify the associated factors.

METHODS

We conducted a cross-sectional study using a structured interviewer-administered questionnaire with HCWs from 120 healthcare facilities in Adamawa and Bauchi States, North-East Nigeria. A knowledge score was created by assigning a point for each correct response. HCWs' knowledge of cholera interventions, calculated as a score, was recoded for ease of interpretation as follows: 0-50 (low); 51-70 (moderate); ≥ 71 (high). Additionally, we defined the inadequacy of HCWs' knowledge of cholera interventions based on a policy-relevant threshold of equal or lesser than 75 scores for an intervention. Multivariable logistic regression was used to identify the factors associated with the adequacy of knowledge score.

RESULTS

Overall, 490 HCWs participated in the study (254 in Adamawa and 236 in Bauchi), with a mean age of 35.5 years. HCWs' knowledge score was high for surveillance/laboratory methods, moderate for case management, WASH, and vaccination, and low for coordination. HCWs' knowledge of coordination improved with higher cadre, working in urban- or peri-urban-based healthcare facilities, and secondary education; cholera case management and vaccination knowledge improved with post-secondary education, working in Bauchi State and urban areas, previous training in cholera case management and response to a cholera outbreak-working in peri-urban areas had a negative effect. HCWs' knowledge of surveillance/laboratory methods improved with a higher cadre, 1-year duration in current position, secondary or post-secondary education, previous training in cholera case management and response to a cholera outbreak. However, HCWs' current position had both positive and negative impacts on their WASH knowledge.

CONCLUSIONS

HCWs in both study locations recorded a considerable knowledge of multi-stranded cholera interventions. While HCWs' demographic characteristics appeared irrelevant in determining their knowledge of cholera interventions, geographic location and experiences from the current position, training and involvement in cholera outbreak response played a significant role.

Epidemiology, diagnostics and factors associated with mortality during a cholera epidemic in Nigeria, October 2020-October 2021: a retrospective analysis of national surveillance data

OBJECTIVES

Nigeria reported an upsurge in cholera cases in October 2020, which then transitioned into a large, disseminated epidemic for most of 2021. This study aimed to describe the epidemiology, diagnostic performance of rapid diagnostic test (RDT) kits and the factors associated with mortality during the epidemic.

DESIGN

A retrospective analysis of national surveillance data.

SETTING

33 of 37 states (including the Federal Capital Territory) in Nigeria.

PARTICIPANTS

Persons who met cholera case definition (a person of any age with acute watery diarrhoea, with or without vomiting) between October 2020 and October 2021 within the Nigeria Centre for Disease Control surveillance data.

OUTCOME MEASURES

Attack rate (AR; per 100 000 persons), case fatality rate (CFR; %) and accuracy of RDT performance compared with culture using area under the receiver operating characteristic curve (AUROC). Additionally, individual factors associated with cholera deaths and hospitalisation were presented as adjusted OR with 95% CIs.

RESULTS

Overall, 93 598 cholera cases and 3298 deaths (CFR: 3.5%) were reported across 33 of 37 states in Nigeria within the study period. The proportions of cholera cases were higher in men aged 5-14 years and women aged 25-44 years. The overall AR was 46.5 per 100 000 persons. The North-West region recorded the highest AR with 102 per 100 000. Older age, male gender, residency in the North-Central region and severe dehydration significantly increased the odds of cholera deaths. The cholera RDT had excellent diagnostic accuracy (AUROC=0.91; 95% CI 0.87 to 0.96).

CONCLUSIONS

Cholera remains a serious public health threat in Nigeria with a high mortality rate. Thus, we recommend making RDT kits more widely accessible for improved surveillance and prompt case management across the country.