Summary
Background: On 24 June 2025, a cholera outbreak was confirmed in Egge Village, Dzaipi Sub-county, Adjumani District. We investigated to determine the source, magnitude, and risk factors associated with the outbreak to inform control and prevention measures.
Methods: We defined a suspected case as the onset of watery diarrhoea and dehydration or death from acute watery diarrhea in a resident (aged ≥2years) of Dzaipi, Arinyapi and Pakele sub-counties, Adjumani District from 1 May to 10 July 2025. A confirmed case was a suspected case with a positive stool culture for Vibrio cholerae. We reviewed health facility records and conducted active case search in the community with the help of local leaders. We conducted descriptive epidemiology and environmental assessment to generate a hypothesis. We conducted an unmatched case-control study and identified risk factors using logistic regression.
Results: We identified 19 cases (4 confirmed and 15 probable) with an attack rate (AR) of 6.4/100,000 and a case fatality rate of 4.3% (1/19). The median age was 38 (IQR: 2-78 years). Males (AR=0.04/100,000) and females (AR=0.09/100,000) were similarly affected. Ajugopi parish was the most affected parish with 15 cases (AR=2.6/100,000). The primary case developed acute watery diarrhoea on 2 June 2025 immediately after returning from the Elegu border point and shared a meal and drinking water at Nyumanzi Reception Centre with the index case (the primary case later died before testing). We observed latrines with compromised sub-structures, open defecation and confirmed faecal contamination of a borehole located 200 metres from a latrine. Drinking untreated borehole water was significantly associated with cholera infection (aOR=5.2; 95% CI: 1.6–17.0). Latrine use (aOR=0.2, 95% CI: 0.05–0.9) and water treatment (aOR=0.2, 95% CI: 0.02–1.4) were protective.
Conclusion: The outbreak was likely imported from South Sudan and amplified by consumption of water from a contaminated borehole in a refugee-hosting community. We recommended boiling or treating water, strengthened border screening, construction of recommended pit latrines and an oral cholera vaccine (OCV) campaign.
Background
Cholera, caused by the bacterium Vibrio cholerae, is characterized by profuse rice-water diarrhea and is primarily transmitted through consumption of water or food contaminated with fecal matter (1). The disease has a short incubation period, ranging from a few hours to five days, with most infected individuals being asymptomatic carriers capable of spreading the infection (2).
Uganda is a cholera-endemic and a priority country for elimination efforts under the Global Task Force on Cholera Control. Hotspots include border districts, refugee-hosting areas, lakeshore communities, and urban slums (3). Adjumani District, located in Northern Uganda, is a key cholera hotspot due to its proximity to South Sudan and its role as a host to over 200,000 refugees, primarily in settlements like Nyumanzi (4). The district’s population of approximately 300,590 faces increased cholera risk from cross-border movement and limited access to safe water and sanitation in refugee settlements. Between 2018 and 2021, Uganda implemented Oral Cholera Vaccination (OCV) campaigns in several high-risk districts, administering two doses 14 days apart to individuals aged 2 years and older, offering up to 80% protection for three years. Despite these efforts, cholera outbreaks persist in Uganda’s endemic districts (5).
On 24 June, 2025, the District Health Officer notified Ministry of Health of a confirmed cholera outbreak in Adjumani District. We determined the source of the outbreak, its magnitude, and risk factors to inform control and prevention measures.
Methods
Adjumani District is located in the West-Nile region of Northern Uganda, bordering South Sudan. The district has a population of 297,894 of which 84,349 are refugees primarily from South Sudan and Sudan residing in settlements like Nyumanzi in Egge village and other 11 settlements (Ayilo 1, Ayilo 2, Baratuku, Boroli, Elema, Mirieyi, Mungula 1, Mungula 2, Nyumanzi Settlement, Olua 1, Olua 2, and Pagirinya). Nyumanzi is the largest refugee settlement in the district with a population of 24,281.
We defined a suspected case as onset of acute watery diarrhoea and dehydration or death from acute watery diarrhea from 1 May to 10 July, 2025 in a resident of Adjumani District aged ≥2 years. A probable case was a suspected case with positive RDT test for V. Cholerae. A confirmed case was a suspected or probable case with positive culture for V. Cholerae from a stool sample. Cases were identified through health facility records review and active case search in the community with the help of local leaders to create a line list. We conducted a descriptive analysis of the cases.
We collected stool samples from 22 cases to confirm the Cholera diagnosis. We also collected 3 water samples from different water sources within most affected community including 3 boreholes for bacteriological culture identification of V. cholerae.
We assessed hygiene conditions at drinking-water and household-water sources including human activities and human waste disposal practices likely leading to water contamination.
We interviewed 19 cases using a case investigation form to generate hypotheses likely associated with this outbreak. We explored the following factors: sources of household water, water treatment practices, food sources, contact with an individual with loose diarrhea, travel history to and from areas with cholera and hand hygiene. We conducted an unmatched case-control study to test the hypothesis, in which we interviewed 19 cases and 76 controls. We defined a control as a resident of Egge village, aged ≥2 years with no history of acute watery diarrhea from 1 May to 10 July, 2025.
This investigation was in response to a cholera outbreak following a directive from Ministry of Health of to investigate this outbreak. The Office of the Associate Director for Science at the Center for Disease Control and Prevention (CDC) Uganda determined that this research did not involve human subject research and that its primary intent was public health practice or disease control. Verbal informed consent was obtained from participants or, if the interviewee was a minor, guardians before the start of each interview.
Results
Descriptive epidemiology
We identified 19 cases (4 confirmed, 15 probable) with an attack rate (AR) of 6.4/100,000. There was 1 death; case fatality rate of (CFR=4.3%). The median age was 38 (IQR: 2-78 years). Females (AR= 0.09/1,000) were slightly more affected than males (AR= 0.04/1,000). Dzaipi was the most affected sub-county with an attack rate of 8.4/10,000. The majority of the cases 84% (16) drank untreated borehole water and none of them received OCV.
The epidemic curve shows a propagated outbreak with point-source introduction followed by person-to-person and waterborne spread. The primary case was a female resident of Egge village who developed acute watery diarrhoea on 2 June 2025 immediately after returning from the Elegu border point with South Sudan, where a large cholera outbreak was ongoing (75,196 cases and 1,383 deaths reported by June 2025) (6). On 2 June 2025, the primary case, in the symptomatic “wet stage” of cholera with acute watery diarrhoea, shared a meal and water likely contaminated with Vibrio cholerae with the first missed case (MN), at Nyumanzi Reception Centre in Dzaipi Sub-County, enabling direct faecal-oral transmission (4). The primary case later died before stool sample collection and testing.
This was followed by MN on 5 June 2025. Two caregivers who had direct contact with MN and likely ingested contaminated water or had inadequate hand hygiene after contact developed symptoms on 8 and 9 June. The index case presented on 10 June 2025, triggering the official notification. Cases continued at 1–2 per day, peaking at three cases on 19 June. No cases were recorded from 21 June to 4 July 2025. A small resurgence occurred on 5 July with two recently arrived refugees from South Sudan (a mother and child) in Nyumanzi settlement, plus an isolated case on 1 July, a health worker who had attended to several cases presenting with acute watery diarrhea and also sought care at Elegu, indicating possible ongoing importation or low-level transmission.
Environmental findings
We found that most of the residents of Egge village collect water for all domestic use from boreholes nearest to their residences. Residents were also seen drinking water directly from the boreholes. We also noted pieces of fecal matter around one borehole in Egge village. The contaminated borehole is located about 200 meters away from a latrine at Nyumanzi HC III.
Hypothesis generation
Out of 19 cases, 16 (84%) depended on borehole water for domestic use, 11 (58%) did not have a pit latrine at home and only 8 (42%) had travelled outside Adjumani District within two weeks before the onset of the disease. Based on the results of the descriptive analysis, we hypothesized that the outbreak was likely imported from South Sudan and amplified by consumption of water from a contaminated borehole in a refugee-hosting community.
Case-control study results
Compared to other primary water sources, drinking untreated water from a borehole in Egge village, Dzaipi sub-county were 5 times more likely to develop acute watery diarrhea relatable to cholera (aOR=5.2, 95% CI: 1.6-17.0). The odds of getting cholera were reduced by using a latrine in a home (aOR=0.2, 95% CI: 0.05-0.9) and treatment of water by any means (aOR=0.2, 95% CI: 0.02-1.4). (Table 1)
Table 1: Risk factors for cholera among residents of Adjumani District, June–July 2025
| Exposure | Cases n (%) |
Controls n (%) |
cOR (95% CI) |
aOR (95% CI) |
|
| Source of water for domestic use | Others (tap water, treated water) | 4 (21%) | 54 (72%) | Ref | Ref |
| Untreated borehole water | 15 (79%) | 21 (28%) | 9.7 (2.9–32) | 5.2 (1.6–17) | |
| Drinking untreated water | Treated (boiled, filtered, chlorinated) | 4 (21%) | 44 (58%) | Ref | Ref |
| Untreated | 15 (79%) | 32 (42%) | 5.2 (1.6–17) | 4.2 (1.4–12.9) | |
| Contact with a diarrhea case | No | 7 (37%) | 58 (76%) | Ref | Ref |
| Yes | 12 (63%) | 18 (24%) | 4.7 (1.7–12) | 4.1 (1.4–12) |
CI: confidence interval, cOR: crude odds ratio, aOR: adjusted odds ratio
No handwashing after latrine use, recent travel to endemic areas and overcrowding were assessed in the multivariable model but were not statistically significant
Discussion
This cholera outbreak was likely imported from South Sudan and amplified by a contaminated borehole in Egge village. South Sudan had experienced a cholera outbreak since October 2024(7). The primary case introduced the infection following cross-border travel from Elegu, with initial transmission occurring through shared contaminated food and water at the overcrowded Nyumanzi Reception Centre in Dzaipi Sub-County. This transmission mode is prevalent in overcrowded refugee settings, where limited access to safe food and water heightens contamination risks (8).
Additional cases included two refugees who arrived from South Sudan already infected and an Elegu health worker who sought care while symptomatic, emphasizing the role of cross-border movement in introducing cholera to Adjumani, a district hosting 84,349 refugees among its 297,894 residents [5,7]. This pattern of disease importation is consistent with outbreaks in other Ugandan border districts, such as Lamwo, where population mobility drives cholera spread (9). These dynamics underscore the challenges of managing infectious diseases in humanitarian settings, where ongoing displacement complicates surveillance and response efforts. Sustained cross-border health coordination and investments in safe food and water provision are essential to prevent recurrent outbreaks in refugee-hosting regions (10). The concentration of cases in Dzaipi Sub- County, a refugee-dense area, highlights how displacement amplifies transmission through shared resources (11).
Study limitation
Given the outbreak context, incomplete case ascertainment may have occurred due to population movement in and out of the settlement, potentially leading to underestimation of the true burden.
Conclusion
The cholera outbreak in Adjumani District, spanning June to July 2025, originated from importation of Vibrio cholerae from South Sudan, subsequently amplified by a contaminated water-source in Egge village, Dzaipi sub-county. The outbreak highlights how easily diseases can spread across border areas.
Public health actions
To stop the propagation of the outbreak, we conducted health education on cholera prevention and use of safe water for domestic use. We educated residents of the affected sub-counties especially those in the refugee settlements and encouraged them to use chlorine releasing tablets that had been provided, to make water safe for consumption and to utilize the prophylactic treatment that had been provided by health care workers. Health care workers were trained on Infection Prevention and Control practices (IPC) and case management.
Recommendations
To prevent future cholera outbreaks in Adjumani District, we recommend that the Government of Uganda, in partnership with local authorities, provide safe drinking water through regular borehole chlorination and monitoring in Egge village and similar refugee-hosting areas. In the long term, the Adjumani District Local Government, in collaboration with the Ministry of Health, Medical Teams International, and other partners, expand latrine availability with improved pit designs and handwashing facilities in Dzaipi Sub-County to reduce faecal contamination and strengthen community health resilience. Additionally, the Ministry of Health, with support from the World Health Organization (WHO) and UNICEF, initiate a district-wide oral cholera vaccine (OCV) campaign targeting refugees and vulnerable host communities to address the absence of prior vaccination and provide up to 80% protection for three years, as demonstrated in previous Ugandan campaigns.
Conflict of interest
The authors declare that they have no conflict of interest.
Authors’ contributions
WJ and MN designed the study and contributed to data collection and analysis. PP and PO also contributed to the study design and data collection. WJ led the writing of the bulletin. PP, PEO, RM, BK, and ARA participated in the writing of the bulletin and review to ensure scientific integrity. All authors contributed to the final draft of the bulletin.
Acknowledgments
The authors would like to thank the Adjumani District Health Team, Nyumanzi HC III administration and staff, and the refugee settlement and reception administration and staff as well as community members of Adjumani District for their support in active case search and line listing of cases during this investigation.
Copyright and licensing
All materials in the Uganda Public Health Bulletin are in the public domain and may be used and reprinted without permission; citation as to source; however, is appreciated. Any article can be reprinted or published. If cited as a reprint, it should be referenced in the original form.
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