Summary
Background: In November 2025, Uganda’s Ministry of Health received reports of community deaths linked to an unknown cutaneous ulcerative illness in Rubirizi District. We investigated to verify the event, describe epidemiology, assess etiologies, health seeking behavior and recommend control measures.
Methods: A suspected case was defined as onset of a painful papule or blister, limb swelling, and a non-healing ulcer lasting >4 weeks with at least one of the following symptoms: fever, general body weakness, headache, loss of appetite, vomiting or abdominal pain in a Rubirizi resident from March–December 2025. We reviewed facility records, verified household cases, conducted active case finding, and collected clinical, exposure, environmental, and health-seeking data. Blood, wound swabs, and biopsies were tested by microscopy, serology, culture, PCR, histopathology, toxicology, and metagenomic sequencing. We conducted 12 key informant interviews on community perceptions and care-seeking.
Results: We identified 18 suspected cases, including 4 deaths (case fatality rate= 22%). Fourteen (78%) were male; median age was 43.5 years (interquartile range: 22–59.5). All had painful ulcers; 17 (94%) had unilateral limb swelling. Cases occurred sporadically, with late October–November clustering; no household had >1 case. Priority infectious, toxic, metabolic, and malignant causes were negative or non-diagnostic. Metagenomic sequencing detected Mycobacteroides abscessus and Paraburkholderia fungorum in two wound swabs, but no definitive etiology was established. Ten cases sought biomedical care, mostly from drug shops; none reported government-facility care. Qualitative findings suggested that delayed formal care-seeking was influenced by distrust of health facilities, fear of poor outcomes after facility attendance, uncertainty about the illness, financial and transport barriers, perceived medicine shortages, and reliance on herbal remedies.
Conclusions: This investigation identified a cluster of chronic painful lower-limb ulcers of undetermined etiology, without evidence of rapid person-to-person transmission. We recommended strengthened surveillance, community engagement, early referral, and advanced diagnostics to guide prevention and control.
Background
Chronic cutaneous ulcers are an important but often underrecognized cause of morbidity in low-resource settings, where delayed diagnosis and limited access to wound care can result in prolonged illness, disability, secondary infection, and death [1-3]. Their causes are diverse and include non-infectious conditions such as diabetes, vascular disease, malignancy, and trauma-related wounds, as well as infectious causes including Buruli ulcer, leishmaniasis, leprosy, lymphatic filariasis, mycetoma, yaws, anthrax, and atypical mycobacterial infections [3-7].
On 26 November 2025, Uganda’s Ministry of Health received an alert about community deaths associated with an unknown illness in Kyabakara Subcounty, Rubirizi District. Initial reports described fluid-filled blisters on the lower limbs that progressed to non-healing ulcers; by 27 November, 13 suspected cases, including 4 deaths, had been reported. We investigated to verify the reported event, describe the epidemiology and clinical features of the cases, assess possible infectious, toxic, metabolic, malignant, environmental, and behavioral contributors, and recommend evidence-based measures for surveillance, case management, community engagement, and prevention.
Methods
Rubirizi District is predominantly rural, with most residents engaged in subsistence farming. The district has an estimated population of 167,527 people across two town councils and nine sub counties and part of Queen Elizabeth National Park is located within the district (Uganda Bureau of Statistics).
We conducted a field investigation to characterize the cluster of cases presenting with an unknown cutaneous ulcer in Rubirizi District, Western Uganda from March to December 2025. A suspected case was defined as onset of a painful papule or blister, limb(s) swelling and non-healing ulcer or >4 weeks with at least one of the following symptoms: fever, general body weakness, headache, loss of appetite, vomiting or abdominal pain in a resident of Rubirizi District between March–December 2025.
We reviewed health facility records and district line list, verified reported cases, and conducted active case finding. Suspected cases were interviewed using a standardized questionnaire to collect sociodemographic, clinical, health-seeking and exposure information. Key informant interviews (KII) were conducted with district health leaders, community leaders, traditional healers, cases and caregivers of deceased cases to explore perceptions of the illness, health-seeking behavior, access to health services, and potential environmental or socio-cultural risk factors.
All identified case-patients were screened for diabetes mellitus. Blood specimens were collected from 10 case-patients and ulcer specimens were collected from 6 case-patients. Specimens were referred to national reference laboratories for testing for viral infections, toxicologic causes, microbiological, antimicrobial susceptibility and histopathological testing. Laboratory investigations included polymerase chain reaction (PCR), serology, microscopy, bacterial culture, and antimicrobial susceptibility testing. Cases were described by person (age, sex, clinical characteristics), place (village, parish, sub county), and time (date of symptom onset). An epidemic curve was constructed to describe the temporal distribution of cases.
The Ministry of Health, Uganda provided administrative clearance to conduct this investigation. Permission to conduct the investigation was obtained from Rubirizi District Health Office. In addition, we received a non-research determination clearance from the US Centers for Disease Prevention and Control (US CDC). This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy. § §See e.g., 45 C.F.R.part 46, 21 C.F.R. part 56; 42 U.S.C. §241(d); 5 U.S.C. §552a; 44 U.S.C. §3501 et seq. All respondents gave individual verbal consent or assent for interviews. We conducted the interviews in privacy to ensure confidentiality and the data kept under password protection by the investigation team.
Results
Descriptive epidemiology of the chronic painful lower limb ulcer cases, Rubirizi District, Uganda, March–December 2025
We identified a total of 18 cases were including 4 deaths (case fatality rate = 22%). Of the 18 cases, 14 (78%) were male and 4 (22%) were female. The overall attack rate was 10/100,000 and the median age was 43.5 (1QR 22-59.5) years. All cases except one presented with unilateral swelling of the limb. All the identified cases had a wound/ulcer hich were painful. Sporadic cases were identified at the parish level across five administrative units in Rubirizi District, Uganda (Figure 1).
The epicurve shows a sporadic pattern of cases occurring throughout the year, with isolated cases reported between March and December 2025 (figure 2). A marked increase began in late October (epidemiological week 44) and the last recorded date of onset was in December 2025
Environmental and laboratory assessment of chronic painful lower– limb ulcer cases, Rubirizi District, Uganda, March Uganda, March–December 2025
Case households generally had poor sanitation and hygiene, and no household had more than one case, providing no evidence of person-to-person transmission. No animal deaths were reported in the affected communities.
Laboratory investigations did not identify a definitive cause. Random blood glucose, complete blood count, and renal function tests results were within normal limits for all patients tested. Investigations for common infectious and non-infectious causes of chronic skin ulcers were largely unremarkable. Ziehl-Nelsen staining of ulcer specimens showed no acid-fast bacteria while filarial antigen testing was negative in all tested patients.
Serological testing identified one patient with a positive leishmaniasis antibody result. Histopathology examination of punch biopsy specimens showed no evidence of malignancy. Culture of wound swab yielded mixed Gram-negative and Gram-positive bacterial organisms. Antimicrobial susceptibility testing was performed to guide clinical management. Anthrax rapid diagnostic tests and PCR were also negative. Metagenomic sequencing identified Mycobacteroides abscessus in two samples. Heavy metals analysis of blood and soil detected iron only; aluminium, arsenic, cadmium, mercury, or lead were not detected.
Healthcare seeking and community perceptions of chronic painful lower–limb ulcer cases, Rubirizi District, Uganda March–December, 2025
Delayed healthcare seeking was common. Of 18 cases, 10 sought biomedical care, most initially obtaining treatment from drug shops, and none reported seeking care at a government health facility. Key informants described fear of death following hospital attendance, limited trust in formal health services, financial and transport constraints, perceived medicine shortages, and beliefs that the illness was caused by witchcraft as barriers to timely care. Herbal remedies were commonly used and were often applied directly to the ulcers.
Discussion
This investigation identified 18 suspected cases of chronic painful lower-limb ulcers, 4 deaths, and did not establish a definitive etiology. Cases occurred sporadically across several parishes, with no household clustering or evidence of rapid person-to-person transmission. However, high case fatality, delayed formal care-seeking, and absence of a confirmed cause made the event an important public health signal.
The clinical syndrome helped narrow the differential diagnosis. Painful distal lower-limb ulcers with unilateral swelling differed from the classic early presentation of Buruli ulcer, which is often painless and commonly affects children in endemic settings [8, 9]. Testing reduced the likelihood of several infectious, toxic, metabolic and other causes. Metagenomic sequencing detected Mycobacteroides abscessus and Paraburkholderia fungorum in two wound specimens. Mycobacteroides abscessus is a rapidly growing, multidrug-resistant nontuberculous mycobacterium that is ubiquitous in soil and water [10]. These findings are hypothesis-generating rather than evidence of causation because organisms detected in chronic wounds may represent colonization, secondary infection or environmental contamination.
A major public health finding was limited formal care-seeking. Although 10 cases sought biomedical care, most obtained medicines from drug shops, and none reported seeking care from a government health facility. Interviews identified distrust, fear of poor outcomes after facility attendance, financial and transport barriers, perceived medicine shortages, and reliance on herbal remedies contributed to avoidance or delay in seeking formal care [11-13]. Strengthen surveillance and referral for unexplained or non-healing ulcers, standardize wound assessment and referral specimen referral, and engage communities, local leaders and traditional healers could support earlier identification and improve diagnosis and management.
Study limitations: The relatively small number of identified cases may limit the extent to which findings can be extrapolated to populations beyond the affected communities. To mitigate this, we conducted an exhaustive active case search through house-to-house visits in all affected villages, reviewed health facility records, and used snowball sampling to ensure we captured every identified case. We also triangulated quantitative findings with qualitative data from 12 key informants and laboratory results, strengthening internal validity.
Laboratory testing was incomplete: metagenomics was performed on only two samples, and confirmatory testing (culture, specific PCR) is pending. To mitigate this limitation, we prioritized sampling from patients with active, untreated ulcers to maximize pathogen yield. Samples were aliquoted and stored at −80°C to enable future testing. We also tested for a broad range of endemic pathogens (filaria, anthrax, Buruli ulcer, leishmaniasis, VHFs, toxicants) to rule out common causes. Results were interpreted cautiously, with clear distinction between preliminary and confirmed findings.
Conclusion: This investigation identified a cluster of chronic painful lower-limb ulcers of undetermined etiology in Rubirizi District. Although the pattern did not suggest rapid person-to-person transmission, the unexplained deaths and delayed formal care-seeking warranted a public health response. Strengthening surveillance, early referral, standardized wound care, community engagement and diagnostic capacity could improve management of similar presentations. Further multidisciplinary investigations integrating clinical, microbiological, pathological, environmental and molecular approaches are needed to determine the underlying cause and guide targeted prevention and control.
Acknowledgements: We acknowledge the participation and support of Rubirizi District Health Team for their leadership, coordination and support during this investigation. We also appreciate the staff of the Central Emergency Reference Laboratory, the National Microbiology Reference Laboratories at the Uganda National Health Laboratory Services, and all other collaborating laboratories for their technical expertise and support in specimen processing and laboratory analysis. We are grateful to the healthcare workers, study participants, and community members whose cooperation made this investigation possible.
Author contributions: DA took lead in conceptualizing the study idea, data collection, data analysis, bulletin article writing and editing. MM, SN, MN, CM, AA were involved in the investigation, data collection, and bulletin writing. RM, BK, NA supervised the investigation, and reviewed the bulletin article. All the authors read and approved the final bulletin article.
Conflict of interest: The authors declare no competing interests.
Copyrights and licensing: All materials in the Uganda Public Health Bulletin is 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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