Cholera remains a significant public health burden in many countries in sub-Saharan Africa, though the exact mechanisms of bacterial emergence and spread remain largely undefined. We generated genomic data from 763 Vibrio cholerae O1 isolates predominantly collected between 2019-2024 to create the largest dataset of V. cholerae genomes sequenced locally in Africa. This dataset enabled us to interrogate recent patterns of spread, including the rapid circulation of the AFR15 lineage associated with unusually large outbreaks in Southern Africa. We provide evidence for the movement of the AFR15 lineage into new African Union Member States and confirm previously observed differences in V. cholerae transmission dynamics in West versus East Africa, though cross-border transmission is prevalent on both sides of the continent. Despite observed differences, evolutionary processes are similar across lineages and we find no evidence for significant changes in antimicrobial resistance genotypes. Overall, our findings emphasize the importance of regionally coordinated cross-border surveillance and interventions, while also demonstrating the critical role of locally generated genomic data in understanding the spread of cholera in Africa.

Enterotoxigenic Escherichia coli (ETEC) remains a major cause of diarrheal morbidity with no licensed vaccines. Role of gut microbiota in vaccine immunogenicity and protection was investigated using 16S rRNA sequencing from the stool samples of 27 volunteers receiving two doses of the live attenuated oral ETEC vaccine ACE527 followed by virulent ETEC H10407 challenge. Systemic and mucosal IgG and IgA responses to heat-labile toxin-B (LTB) and colonization-factor-antigen-I (CFA/I) were quantified by ELISA in serum and antibody-in-lymphocyte-supernatant (ALS). Microbiome α-diversity, β-diversity, and taxa-immune associations were evaluated using regression models, MiRKAT, and relaxed LASSO. Vaccination increased (~ 25-30%) Eubacterium_brachy_group, Family_XIII_AD3011 and Actinomyces. Higher α-diversity (inverse-Simpson) was associated with reduced ALS anti-LTB and CFA/I IgA responses, whereas β-diversity correlated with increased serum anti-CFA/I IgA. Members of Anaerovoraceae, Peptostreptococcaceae, Oscillospiraceae, and Veillonellaceae enhanced immune responses and protection against severe diarrhea and ETEC colonization, while Ruminococcaceae, Sutterellaceae, Coriobacteria, Clostridia, and Actinobacteria showed antagonistic associations.

The October 2023 to 2024 cholera outbreak demonstrates significant challenges related to water quality and sanitation, especially in peri-urban areas with limited access to clean water. This study assesses the presence of faecal coliforms and Escherichia coli (E. coli) in drinking water sources across five townships, identified as cholera transmission hotspots, two months post the cholera outbreak in the Lusaka District. A total of 169 water samples were collected from protected sources, treated piped water, and unprotected sources, including dams and shallow wells. Faecal coliforms and E. coli were detected across all source types. Among unprotected sources, 92.3% (12/13) of samples contained ≥100 CFU/100 mL of both faecal coliforms and E. coli. Protected sources showed variable contamination, with 18.3% exceeding ≥100 CFU/100 mL for faecal coliforms and 15.4% for E. coli. Treated water sources showed the lowest contamination, with 88.5% of samples having no detectable faecal coliforms and 90.4% having no detectable E. coli. Zero-inflated negative binomial regression showed that treated water sources were associated with substantially lower faecal coliform counts compared with protected sources (PR = 0.11, 95% CI: 0.03–0.35), while unprotected sources exhibited higher contamination intensity (PR = 1.77, 95% CI: 0.94–3.31). Treated sources were significantly more likely to be structurally free of contamination, whereas unprotected sources had an extremely low probability of yielding zero counts. These findings indicate that current water safety conditions in Lusaka’s cholera hotspot areas remain inadequate for preventing faecal-oral transmission.

BACKGROUND:The aim of this prospective cohort study is to build evidence on transmission dynamics and risk factors for Vibrio cholerae infections in cholera patient households. METHODS:Household contacts of cholera patients were observed for 1 month after the index cholera patient was admitted to a healthcare facility for stool, serum, and water collection in urban Bukavu in South Kivu, Democratic Republic of the Congo. A V. cholerae infection was defined as a V. cholerae bacterial culture positive result during the 1-month surveillance period and/or a 4-fold rise in a V. cholerae O1 serological antibody from baseline to the 1-month follow-up. RESULTS:Sixty-seven percent of cholera patient households (56/83) had ≥1 V. cholerae infected contact during the 1-month surveillance period. Twenty-seven percent of contacts (134 of 491) of cholera patients had a V. cholerae infection. Twelve percent (9 of 77) of cholera patient households had a stored water sample with V. cholerae by bacterial culture, and 7% (5 of 70) for water sources. Significant risk factors for symptomatic V. cholerae infections among contacts were stored food left uncovered (odds ratio (OR): 2.39, 95% confidence interval (CI): 1.13, 5.05) and younger age (children <5 years) (OR: 2.09, 95% CI: 1.12, 3.90), and a drinking water source with >1 colony forming unit Escherichia coli 100 mL (OR: 3.59, 95% CI: 1.46, 8.84) for V. cholerae infections. None of the contacts residing in households where the index patient consumed doxycycline in the past 48 hours had a V. cholerae infection compared with 28% of contacts (133 out of 470) where the index patient did not consume doxycycline (P = .005). CONCLUSIONS:The findings indicate a high risk of cholera among contacts of cholera patients in this urban cholera endemic setting, and the need for targeted water treatment and hygiene interventions to prevent household transmission of V. cholerae.

Background:Despite ongoing containment and vaccination efforts, cholera remains prevalent in many countries in sub-Saharan Africa. Part of the difficulty in containing cholera comes from our lack of understanding of how it circulates throughout the region, so this study uses genomic epidemiology to identify disease transmission patterns in Southern and Eastern Africa. Methods:To better characterize regional transmission, we performed whole genome sequencing on 142 Vibrio cholerae samples of different sample types, each collected between 2007-2019 from five different countries in Southern and Eastern Africa. We obtained 114 high quality V. cholerae genomes that we combined with 1385 previously published genomes to conduct phylogenetic and other analyses used to better understand cholera transmission and circulation in Southeastern Africa. Findings:We showed that V. cholerae sequencing can be successful from a variety of sample types and filled in spatial and temporal gaps in our understanding of circulating lineages, including providing some of the first sequences from the 2018-2019 outbreaks in Uganda, Kenya, Tanzania, and Malawi. Our results present a complex picture of cholera transmission in the region, with multiple lineages found to be co-circulating within several countries. Interpretations:Our findings suggest that previously identified sporadic cases may be from larger, undersampled outbreaks, highlighting the need for careful examination of sampling biases and underscoring the need for continued and expanded cholera surveillance across the African continent.

Background:Effective cholera outbreak response requires accurate bedside rapid diagnostic tests (RDTs) because access to laboratories is often limited. Formative studies suggest cholera diagnostics have multiple vulnerabilities, including antibiotics and predation by bacteriophage ('phage') specific to Vibrio cholerae (Vc). Methods:We conducted a prospective nationwide study in Bangladesh among over 2000 patients with diarrhoeal disease to characterize how these vulnerabilities impact RDT performance. Assays included culture, qPCR and mass spectrometry. Findings:With the current gold standard of culture or qPCR Vc positivity, we found no effect of phage on RDT performance. When the diagnostic criteria were expanded to include phage, there was a small decrease in RDT sensitivity. In contrast, large increases in sensitivity and specificity were observed among patients with moderate and severe dehydration. Using the expanded definition, the odds of RDT positivity decreased among cholera patients with phage exposure. The effect was most robust among patients with severe dehydration. Antibiotic were detected in over 80% of samples by LC-MS/MS which limited testing for effects on RDTs. Applying these findings, we estimated that restricting RDT use to severe patients with no reported antibiotic exposure increases sensitivity by 50% compared to unrestricted use. If phage were a diagnostic proxy for Vc, we estimate RDT would miss an additional 17% of cholera cases. Interpretation:Cholera RDTs have critical limitations that require consideration in global deployments. Inclusion of phage detection in diagnostic criteria may improve case detection which requires further study. The impact of these findings likely extends to other diseases where diagnostics share similar vulnerabilities.

Background:The prevalence of ETEC in the environment could be influenced by environmental factors, which may contribute to seasonal outbreaks. This study assessed the seasonal prevalence of the ETEC population in water bodies in relation to ecological changes in Bangladesh. Method:The presence of ETEC in water, plankton, and sediment samples collected from water bodies in Mathbaria, a southern coastal region, was investigated using quantitative PCR (qPCR) and an extensive culture method over a year. Concurrently, the physico-chemical parameters of the water were measured. We also tested aquatic samples from Chhatak, a northern hilly region. Results:ETEC was detected in a high proportion (56%-78%) in water, plankton, and sediment samples from both sites. In Mathbaria, higher abundance of ETEC was noted in fall and spring, followed by summer and lowest in the monsoon. ETEC positivity was high in winter by qPCR, but no viable ETEC could be isolated. Environmental conditions such as neutral to low alkaline pH, elevated dissolved oxygen levels, and warmer water temperatures showed a trend of association with increased ETEC prevalence. Conclusion:The persistence of ETEC in environmental water and their association with ecologic factors may help to explain seasonal illnesses in people.

Enterotoxigenic Escherichia coli (ETEC) causes significant morbidity, mortality, and growth faltering among children, particularly in low- and middle-income countries. While gut inflammation contributes to growth faltering, the role of ETEC in inflammation remains poorly understood. We previously demonstrated that ETEC-producing heat-labile toxin (LT) and heat-stable toxins (ST) induced significant inflammation in humans, but LT-ETEC strains are understudied. In this study, we evaluated the intestinal inflammation induced by the LT-ETEC strain LSN03-016011/A in a human challenge model. Stool samples were analyzed for pre- and post-challenge myeloperoxidase (MPO) and pro and anti-inflammatory cytokines, ETEC shedding, and ETEC-specific antibody responses. MPO, IL-1β, and CXCL-8 levels significantly increased post-ETEC challenge, but there was no significant difference between symptomatic and asymptomatic participants. Participants protected from severe diarrhea had higher levels of pre-challenge IL-10, IL-13, and IFN-γ compared to those not protected. The MPO and specific cytokine levels were significantly correlated with the seroconversion status to LT and the colonization factor antigen CS17. This study provides evidence that LT-ETEC strain can induce significant intestinal inflammation even in the absence of symptoms, highlighting the need for a vaccine and a better understanding of the impact of ETEC-attributable inflammation on child health in endemic areas.

Background: We assessed whether the Preventative-Intervention-for-Cholera-for-7-Days (PICHA7) program reduced diarrhea and improved child growth in the Democratic Republic of the Congo (DRC). Methods: The PICHA7 cluster-randomized controlled trial enrolled diarrhea patient households in urban Bukavu, DRC. Households were randomized into two arms: single in-person visit for the DRC governments diarrhea patient standard message on oral rehydration solution use and a basic WASH message (standard arm); or this standard message and the PICHA7 program with quarterly in-person visits and weekly voice and text mobile health messages (mHealth) (PICHA7 arm). The primary outcome was diarrhea in the past two weeks assessed monthly for 12 months. Secondary outcomes were diarrhea with rice water stool, healthcare facility visits for diarrhea, stunting, underweight, and wasting over 12 months. Generalized estimating equations were used for regression models to account for clustering at the individual and household level. Results: Between December 2021 and December 2022, 2334 participants in 359 households were randomly allocated to two arms: 1138 standard arm and 1196 PICHA7 arm. Diarrhea prevalence during the 12 month surveillance period was significantly lower among PICHA7 arm participants (Prevalence Ratio: 0.39 (95% Confidence Interval (CI): 0.32, 0.48). PICHA7 arm participants had lower odds of diarrhea with rice water stool (Odds Ratio (OR): 0.48 (95% CI: 0.27, 0.86)), and lower odds of visiting a healthcare facility for diarrhea during the 12 month surveillance period (OR: 0.44 (95% CI: 0.25, 0.77)). PICHA7 arm children 0-4 were significantly less likely to be stunted (52% vs. 63% standard arm) (OR: 0.65 (95% CI: 0.43, 0.98)) at the 12 month follow-up. All WASH components had high adherence. Conclusion: The PICHA7 program which combines mHealth with quarterly in-person visits lowered diarrhea prevalence and stunting in the DRC. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial NCT05166850 ### Funding Statement This work was made possible with funding from Wellcome and UK aid from the Foreign and Commonwealth Development Office grant number 215674Z19Z and 1R01AI148332-01 provided to Christine Marie George at Johns Hopkins School of Public Health. The views expressed do not necessarily reflect FCDOs official policies or views. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: We received ethical approval for this study from the institutional review boards of the Johns Hopkins School of Public Health and Catholic University of Bukavu. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors.

Cholera rapid diagnostic tests (RDTs) can strengthen existing surveillance systems by offering a cost-effective screening method that improves understanding of cholera burden allowing for targeted prevention and control efforts. The RDT Implementation Strategy and Evaluation (RISE) project is the pilot study for Gavi's innovative Diagnostic Procurement Platform which provides cholera RDTs to enhance national surveillance. Implementation of cholera RDTs was evaluated following their distribution in 2023 to facilities within Nepal's Early Warning and Reporting System (EWARS). Quantitative data was collected through EWARS surveillance reports, national-level and individual-level REDCap surveys from select facilities in Kathmandu. Key-informant interviews were also conducted in Kathmandu with personnel involved in cholera surveillance and response. Interviews were conducted using a semi-structured interview guide and analyzed according to inductively identified themes. Qualitative findings indicated generally positive perceptions of cholera RDTs, highlighting their speed and ease of use, and suitability for deployment in under-resourced areas by unskilled personnel. However, a lack of awareness of the RDTs, limited training, and concerns about the RDTs' quality, availability, and costs were challenges raised consistently. Quantitative findings revealed underreporting of acute gastroenteritis (AGE) and cholera in EWARS and an underutilization of the cholera RDTs, with only 2.6% of reported AGE cases screened using an RDT. This field evaluation demonstrated that RDTs can have an important role in cholera surveillance but highlighted significant challenges with cholera lab capacity, reporting, and training. Both the qualitative and quantitative findings showed gaps in surveillance reporting, which were exacerbated by the complexity of adding RDTs without strong guidance as well as beliefs about the RDTs' poor validity. These misconceptions and challenges need to be addressed at the local and national level to successfully scale-up cholera RDTs in Nepal and beyond.

The integration of rapid diagnostic tests (RDTs) into cholera surveillance marks a pivotal shift in global cholera control strategies. In 2024, Gavi, the Vaccine Alliance initiated the shipment of cholera RDTs to cholera-endemic countries via Gavi diagnostic support, aligning with the publication of the Global Task Force for Cholera Control (GTFCC) surveillance for cholera guidance. The GTFCC guidance recommends systematically testing suspected cases of cholera with RDTs. Implementing these tests at scale requires substantial changes to health systems spanning logistics, operations, and finance, such as supply chain adaptations, training key personnel, and integrating RDTs into national surveillance systems. Competing health priorities and declining global health funding further complicate implementation efforts. Additionally, although RDTs are valued for their speed and accessibility, concerns about their diagnostic accuracy remain. This is despite GTFCC guidance-based on prospective studies and systematic reviews-confirming that their performance is sufficient to support expanded use for early outbreak detection and monitoring. This Personal View argues that RDT-driven surveillance can close long-standing data gaps, refine burden estimates, and improve targeted interventions, such as vaccines, through early outbreak detection and rapid response. Despite complex factors that must be accounted for during implementation, with sustained support from Gavi and the GTFCC, the roll-out of RDTs for cholera is a major step towards achieving the 2030 cholera elimination goals.

No licensed vaccines are available for the largely antibiotic-resistant Shigella or enterotoxigenic Escherichia coli (ETEC), the two most common bacteria causing children's diarrhea and travelers' diarrhea. Virulence heterogeneity is a key obstacle to developing vaccines against Shigella or ETEC. By applying a multiepitope fusion antigen (MEFA) vaccinology platform, we recently constructed epitope- and structure-based polyvalent proteins to induce cross-protective antibodies against heterogeneous Shigella or ETEC strains. In this study, we combined a polyvalent Shigella protein with two polyvalent ETEC proteins, examined antigen compatibility and broad immunogenicity, and evaluated the potential of developing a combined vaccine against the two groups of bacteria. Data showed that mice intramuscularly immunized with the combined vaccine candidate (ShecVax) developed antibodies to all the following target virulence factors: Shigella IpaB, IpaD, VirG, GuaB, StxA, Stx2A, and StxB, and ETEC STa, LT, CFA/I, CS1, CS2, CS3, CS4, CS5, and CS6. ShecVax-induced antibodies significantly inhibited the invasion of all Shigella species and important serotypes, prevented the adherence of all important ETEC pathotypes, and neutralized the enterotoxicity of ETEC toxins STa and LT. Moreover, ShecVax prevented mice from lethal pulmonary infection with Shigella sonnei or S. flexneri 2a, significantly reduced ETEC bacterial colonization in rabbit small intestines, and passively protected newborn pigs against ETEC toxin-mediated clinical diarrhea. These results indicated that ShecVax is broadly immunogenic and cross-protective against Shigella and ETEC, suggesting ShecVax can be a Shigella/ETEC combined vaccine against children's and travelers' diarrhea, and the MEFA platform can be generally applied for vaccine development against heterogeneous pathogens or different diseases.IMPORTANCEThere are no effective countermeasures against Shigella and enterotoxigenic E. coli (ETEC), two antibiotic-resistant groups of bacteria and the leading causes of diarrhea in children in developing countries (children's diarrhea) and international travelers (travelers' diarrhea). Vaccines are a more practical approach to protect against infectious diseases, including diarrhea caused by Shigella or ETEC. A combined vaccine cross-protective against Shigella and ETEC can save hundreds of thousands of lives and prevent hundreds of millions of diarrhea cases yearly; it can also reduce antibiotic prescription and decrease antibiotic resistance, thus significantly improving global health. In addition, we may apply the MEFA platform to develop combined vaccines against heterogeneous pathogens or different diseases to accommodate an increasingly crowded expanded program on immunization (EPI).

Background:Cholera is a public health threat in resource-limited settings and is responsible for causing over 3 million cases globally. Mucosal immune responses play an important role in protecting against Vibrio cholerae infection, a non-invasive mucosal pathogen, yet traditional plasma-based assays are invasive and logistically challenging, particularly during outbreaks in low- and middle-income countries (LMICs). Saliva offers a unique window into mucosal immunity and may serve as a non-invasive alternative for seroprevalence and vaccine immunogenicity studies. Methods:We conducted a cross-sectional antibody profiling study to analyse cholera-specific antibodies in saliva and plasma samples from 74 participants upon presenting to the cholera treatment centres. These were collected from four treatment centres in Lusaka during Zambia's most severe cholera outbreak in 2024 caused by Vibrio cholerae O1 Ogawa. Levels of total IgG, IgG1-3, IgM, secretory IgA, and IgA1-2 isotypes were used to compare the biomarker profile between the two sample types. Results:Saliva and plasma antibody profiles were comparable, with elevated IgA1 and IgA2 responses to cholera toxin-B (CtxB), sialidase, HlyA, and TcpA in saliva. Broader systemic responses were seen in plasma, including high CtxB-specific IgM, IgA1, and total IgG levels. Notably, biomarkers such as HlyA, Ogawa O-specific polysaccharide (OSP), and sialidase exhibited significant positive correlations between plasma and saliva. Elevated biomarker levels of HlyA, Ogawa O-specific polysaccharide (OSP), and sialidase in people living with HIV/AIDS (PLWHA) suggested immunological differences that warrant further exploration. Conclusion:We demonstrate that saliva is a viable, non-invasive alternative for cholera antibody-based profiling, offering practical advantages in resource-constrained settings. Given its strong correlation with systemic antibody profiles, saliva may be a practical sample for sero-surveillance in resource-limited settings. Future studies should investigate the duration of these salivary responses to further substantiate their use in estimating disease burden and immunity.

Objective: Globally, there are estimated to be 2.9 million cholera cases annually. Early detection of cholera outbreaks is crucial for resource allocation for case management and for targeted interventions to be delivered to stop the spread of cholera. In resource limited settings such as Eastern Democratic Republic of the Congo (DRC), there is often limited laboratory capacity for analysing stool samples for cholera by bacterial culture. Therefore, rapid diagnostic tests (RDTs) for cholera present a promising tool to rapidly test stool samples in a health facility setting for cholera. Our objective is to evaluate the Crystal VC O1 RDT for cholera detection compared with bacterial culture and polymerase chain reaction (PCR) for Vibrio cholerae. Methods: From March 2020 to December 2022, stool samples were collected from 644 diarrhoea patients admitted to 94 health facilities in Bukavu in Eastern DRC. Patient stool samples were analysed by Crystal VC O1 RDT for cholera and by bacterial culture and PCR for V. cholerae O1. Results: Twenty six percent of diarrhoea patients (166/644) had stool samples positive for cholera by RDT, and 24% (152/644) had stool samples positive for V. cholerae O1 by bacterial culture or PCR. The overall specificity and sensitivity of the Crystal VC O1 RDT by direct testing was 94% (95% confidence interval [CI]: 92%-96%) and 90% (95% CI, 84%-94%), respectively, when compared with either a positive result by bacterial culture or PCR. Conclusion: Our findings suggest that the Crystal VC O1 RDT presents a promising tool for cholera surveillance in this cholera endemic setting in sub-Saharan Africa.

Saliva, as a diagnostic medium, offers a promising alternative to blood by virtue of its non-invasive collection, which enhances patient compliance, especially in paediatric and geriatric populations. In this study, we assessed the utility of saliva as a non-invasive medium for measuring Vibrio cholerae-specific serum antibodies in naturally infected individuals. We tested paired serum and saliva samples obtained from a total of 63 patients with cholera enrolled in a cohort study. Vibriocidal antibodies assay (IgM/IgG) as markers for accurate determination was used to determine cholera-specific antibody levels. Using receiver operating characteristics (ROC) curve, we found that the best cut-off that maximizes (sensitivity + specificity) is 10 titres. At this saliva titre, the sensitivity is 76.9% (95%CI: 60.9%, 87.7%) and specificity is 80.0% (95%CI: 56.6%, 92.5%). Using Spearman's correlation coefficient, we also found evidence of a positive correlation between V. cholerae saliva and serum antibodies (rho = 0.66, P < 0.001). In conclusion, saliva-based diagnostic cholera tests have high diagnostic accuracy and would be advantageous, cheaper, and quicker for early diagnosis of severe cholera outcomes.

(1) Shigella spp. (Shigella) is known for causing dysentery with blood in stool, but most children infected with Shigella have non-dysentery Shigella-associated diarrhea (NDSD). The World Health Organization recommends the use of antibiotics when diarrhea is bloody, leaving most NDSD cases untreated. The absence of dysentery may not indicate a low risk of death and severe morbidity. Rapid diagnosis and treatment of shigellosis in vulnerable, young children may be lifesaving. INSIGHT aims to determine the potential benefit of identifying NDSD cases (n = 296) and their outcomes compared to cases of Shigella dysentery [DS (n = 148)] and non-Shigella watery diarrhea [WD (n = 148)]. (2) Children seeking care at hospitals in Bangladesh will be enrolled and followed for 1 year (NDSD and DS) or 90 days (WD). We will determine the impact of NDSD on morbidity, mortality, gut health, nutritional status, and cognitive development compared to DS and WD in children and whether the simple “Rapid LAMP-based Diagnostic Test (RLDT)” can accelerate the detection and treatment of shigellosis in the clinical settings of rural Bangladesh. (3) INSIGHT will determine the impact of NDSD in children and determine if the treatment guidelines of shigellosis need to be revisited to improve clinical outcomes and the development of these children.

This study investigated whole-cell oral cholera vaccine (kOCV) single-dose effectiveness and transmission dynamics of Vibrio cholerae through 4 years of epidemiological and genomic surveillance in Democratic Republic of the Congo (DRC). Whole genome sequencing was performed on clinical and water V. cholerae strains from 200 patient households and found annual bimodal peaks of V. cholerae clade AFR10e. 1154 diarrhea patients were enrolled with 342 culture confirmed cholera patients. A large clonal cholera outbreak occurred 18 months after a kOCV campaign of >1 million doses of Euvichol-Plus, likely because of low vaccine coverage in informal settlements (9%). Clinical and water V. cholerae strains in the same household were more closely related than different households suggesting both person-to-person and water-to-person transmission. Single-dose kOCV vaccine effectiveness in the first 24 month after vaccination was 56.9% (95% CI: 18.6%-77.2%), suggesting a single-dose provided modest protection against medically attended cholera during the 24 months post-vaccination.