Summary
Background: In February 2026, Amolatar District in Northern Uganda reported a measles outbreak among children admitted into high-volume health facilities. We investigated to determine the magnitude of the outbreak, identify risk factors for infection, and assess vaccination coverage to recommend control measures.
Methods: We defined a suspected case as fever and maculopapular rash with ≥1 of cough, coryza, or conjunctivitis in an Amolatar District resident from November 1, 2025–February 20, 2026. A confirmed case was a suspected case with a positive measles-specific IgM test. Cases were identified through medical records review and active community search. We calculated attack rates (AR) by age, sex, and subcounty. We conducted an unmatched case-control study (1:3) and used logistic regression to identify risk factors. Controls were community-based and randomly selected from the same sub-counties as the cases. We estimated vaccination coverage (VC) using the proportion of vaccinated controls.
Results: We identified 120 cases (5 confirmed, 115 suspected); 75(63%) were female. Children aged 9–17 months (AR:360/100,000), females (AR:79/100,000), and Akwon Subcounty (AR:690/100,000) were most affected. The outbreak was propagated following a burial with peaks in November 2025 and January–February 2026. In a case-control analysis (87 cases and 261 controls), 44(51%) of cases and 176(67%) controls had received at least one dose of measles vaccine, while 23(26%) cases and 113(43%) controls had received both doses. Attending burial ceremonies (aOR=2.41;95%CI:1.21–4.78) and household crowding (aOR=3.38;95% CI:1.85–6.17) increased the odds of infection. Vaccination with one dose was protective (aOR=0.50; 95%CI:0.28–0.88) with a coverage of 67%.
Conclusion: Attending burial ceremonies, household crowding, and low vaccination coverage fueled measles transmission. Mass vaccination to increase coverage and strengthen surveillance and risk communication during social gatherings could prevent similar future outbreaks.
Introduction
Measles is a highly contagious, vaccine-preventable disease caused by the measles virus. [1]. It spreads primarily through inhalation of respiratory droplets or direct contact with an infected individual [2]. Due to its high transmissibility, where a single infected person can transmit the virus to 12–18 susceptible individuals, measles poses a significant public health threat, especially in areas with low immunisation coverage [3]. The disease has an incubation period of 7–21 days and presents with a characteristic maculopapular rash, fever, cough, coryza (runny nose), and conjunctivitis [4]. In severe cases, patients may develop complications such as corneal ulcers (wounds in the black spot of the eye), otitis media (ear discharge), and pneumonia (difficulty in breathing) [5].
Globally, measles remains one of the leading causes of death among young children, with over 95% of measles-related fatalities occurring in developing countries [6]. The disease can be effectively prevented through the Measles-Rubella (MR) vaccine, which in Uganda is administered in two doses at 9 and 18 months of age [7]. The World Health Organisation (WHO) recommends at least 95% vaccination coverage to establish herd immunity and interrupt transmission [8]. Additionally, timely isolation of suspected and confirmed cases is critical to curbing the spread of the virus [9].
In February 2026, measles emerged as a critical public health threat in Amolatar District, Uganda, when the Uganda Virus Research Institute (UVRI) confirmed an outbreak in the sub-counties of Akwon, Muntu, and Arwotcek following laboratory confirmation of five suspected cases. We estimated the magnitude, identified the source of the outbreak, assessed risk factors for transmission, established the vaccination coverage and vaccine effectiveness, and recommended evidence-based control and prevention measures.
Methods
We investigated in Amolatar District in Lango sub-region, Northern Uganda (Figure 1). The district comprises thirteen (13) sub-counties and two (2) town councils. However, Muntu and Akwon subcounties lacked vaccination health facilities. The investigation was conducted in Akwon and Muntu Subcounties, the areas most affected by the measles outbreak.
We defined a suspected case as onset of fever and maculopapular rash plus ≥1 of the following symptoms cough, coryza (runny nose), or conjunctivitis (red eyes), in a resident of Amolatar District from November 1, 2025–February 20, 2026; and a confirmed case was as a suspected case with laboratory confirmation of measles-specific IgM antibodies in a resident Amolatar District from November 1, 2025–February 20, 2026. We line-listed suspected cases by reviewing health facility records. We used standard case investigation forms to collect data on patients’ demographics, clinical characteristics, vaccination status, exposure history, and treatment and admission history.
We constructed an epidemic curve to determine the distribution of measles cases over time. We computed Attack Rates (AR) by person and place, using projected populations from Uganda Bureau of Statistics (UBOS) as the denominator. We described AR by place, depicting it on maps using Quantum Geographic Information System (QGIS)
We conducted 15 hypothesis-generating interviews with case patients using the measles investigation form. We asked caregivers about potential sources of exposure and interviewed the District Health Team (DHT) about these factors. We conducted an unmatched case-control study to evaluate the hypotheses generated. We recruited 87 case patients and 3 controls per case. We identified factors associated with measles using logistic regression.
We estimated VC using the percentage of controls with a history of measles in the case-control study, assuming that the controls were representative of the general population. We calculated VE using the formula: VE = (1 − aOR) × 100%, where aOR is the adjusted odds ratio for having received at least one dose of measles vaccine, estimated by conditional logistic regression and adjusted for risk factors significant in the univariate analysis.
The Ministry of Health of Uganda issued a directive and approved the investigation of this outbreak. The office of the Associate Director for Science at the US Centres 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 consent was obtained from participants or, if the interviewee was a minor, from their guardians before the start of the interview.
Results
Descriptive epidemiology
We identified 120 cases (86 suspected, 29 probable, and 5 confirmed), with no deaths. The epidemic curve shows a propagated pattern with multiple peaks (Figure 1). The outbreak began in Akwon Sub-County in November 2025 and progressively spread to other sub-counties, with sustained person-to-person transmission peaking in early February 2026.
All cases presented with fever and generalised rash. Additionally, 86/120 (72%) had coryza, 85/120 (71%) had cough, 42/120 (35%) had conjunctivitis, and 3/120 (3%) had diarrhoea. The attack rate was higher among females (79/100,000) compared to males (49/100,000). By age group, the highest attack rate was observed in children aged 9–17 months (360/100,000), followed by those aged 0–8 months (167/100,000) and 18–59 months (159/100,000). The attack rate declined steadily with increasing age, with the lowest among individuals aged 15 years and older (22/100,000). Overall, the attack rate was 64/100,000 across both sexes and age groups. Attack rates varied across Amolatar District, with Akwon Sub-County recording the highest at 690/100,000, followed by Muntu Sub-county at 120/100,000 (Figure 2).
Hypothesis generation and case-control study findings
Of the 87 cases interviewed, 44 (50%) were not vaccinated, 43 (50%) hadn’t received any measles vaccine, and 40 (57%) had a symptomatic case patient.
Risk factors for measles infection during an outbreak, Amolatar District, Uganda
Receipt of one measles-rubella vaccine dose was independently protective against measles infection (aOR=0.48; 95%CI:0.26–0.89; p=0.019), corresponding to approximately 52% lower odds of infection. Household exposure remained a significant risk factor for measles transmission, with individuals reporting a household member with measles having more than three times higher odds of infection compared to those without household exposure (aOR=3.38;95% CI:1.85–6.17; p<0.001) (Table 1).
Table 1: Risk factors for measles outbreak in Muntu and Akwon sub-counties, Amolatar District, Uganda, November 2025–February 2026 (n=261)
| Risk factor | Number (% exposed) | cOR (95% CI) | p-value | aOR (95% CI) | p-value | |
| Cases n (%) | Controls n (%) | |||||
| Attending school | ||||||
| No | 72 (82.8) | 230 (88.1) | Ref | – | Ref | – |
| Yes | 15 (17.2) | 31 (11.9) | 1.54(0.78–3.02) | 0.20 | 1.28 (0.60–2.73) | 0.52 |
| Visited social function | ||||||
| No | 63 (72.4) | 232 (88.9) | Ref | – | Ref | – |
| Yes | 24 (27.6) | 29 (11.1) | 3.05(1.65–5.60) | <0.001 | 2.41 (1.21–4.78) | 0.012 |
| Household member with measles | ||||||
| No | 49 (56.3) | 220 (84.3) | Ref | – | Ref | – |
| Yes | 38 (43.7) | 41 (15.7) | 4.16(2.41–7.18) | <0.001 | 3.38 (1.85–6.17) | <0.001 |
| Measles vaccination | ||||||
| No | 43 (49.4) | 85 (32.6) | Ref | – | Ref | |
| Yes | 44 (50.6) | 176 (67.4) | 0.49(0.30–0.79) | 0.004 | 0.50 (0.28–0.88) | 0.0016 |
| Measles vaccination (MR doses) | ||||||
| No dose | 43 (49.4) | 85 (32.6) | Ref | – | Ref | – |
| One dose | 23 (26.4) | 113 (43.3) | 0.40(0.22–0.71) | 0.002 | 0.48 (0.26–0.89) | 0.019 |
| Two doses | 21 (24.1) | 63 (24.1) | 0.66(0.35–1.21) | 0.20 | 0.72 (0.38–1.36) | 0.31 |
Measles vaccine coverage and vaccine effectiveness
The estimated VE was 50% (95%CI= 12%-72%). The estimated VC based on the percentage of controls with a history of measles vaccination was 67%.
Discussion
Children aged 9-17months and females were most affected during the outbreak. Attendance at social gatherings and household exposure were associated with measles infection, while receipt of measles-containing vaccine was protective. These findings are consistent with the well-established epidemiology of measles and highlight the role of close-contact exposure and immunity gaps in facilitating transmission. Household exposure was the leading risk factor for measles infection in this investigation. This is consistent with the high transmissibility of measles in close-contact settings [10, 11]. The concentration of cases within households reflects sustained airborne exposure when infectious and susceptible individuals share living space over prolonged periods.
Social gatherings and community events were significant settings for transmission. Crowding increased contact between infectious and susceptible individuals[9]. In populations with incomplete vaccination coverage and herd immunity thresholds not met, even brief exposures in congregate settings can initiate chains of transmission that extend well beyond the initial event.
A large proportion of cases occurred in unvaccinated children, highlighting the role of measles vaccination. With one dose approximately 93% effective and two doses approximately 97% effective, the accumulation of unvaccinated children across successive birth cohorts creates susceptible pools that sustain and amplify outbreaks once measles is introduced into the community [12]. The observed vaccination coverage was below the level required for herd immunity, suggesting immunity gaps in affected communities. These gaps may have resulted from missed vaccination opportunities, barriers to access, or weaknesses in the routine immunisation system, particularly poor documentation and incomplete vaccination records [13]. This made it difficult to identify and follow up children who had missed doses, allowing susceptible individuals to accumulate over time.
School attendance was not a significant risk factor in this outbreak, indicating transmission was primarily community-based rather than school-driven. This aligns with evidence from other settings where uneven vaccination coverage creates immunity gaps at the community level, favouring community transmission over institutional amplification [14]. The absence of a school-based signal suggests susceptibility was distributed broadly across households and community spaces rather than concentrated in any single institutional setting.
Study limitations: This study had several limitations. Recall and information may have affected the accuracy of reported exposures and vaccination histories, potentially misclassifying cases and influencing estimated associations. Residual confounding from unmeasured factors such as population mobility and contact patterns, as well as possible selection bias in control recruitment, are additional limitations. Finally, findings are specific to Muntu and Akwon sub-counties and may not be generalizable to other settings.
Conclusion: The measles outbreak in Muntu and Akwon sub-counties was primarily driven by immunity gaps, delayed detection, and weaknesses in surveillance and reporting systems. Household exposure and social gatherings facilitated transmission, while measles vaccination provided protection, although vaccine effectiveness appeared lower than expected. The findings underscore the need to strengthen routine immunisation, improve surveillance and early case detection close immunity gaps and prevent future outbreaks.
Recommendations: Strengthening routine immunisation through targeted outreach, improved service delivery, and effective defaulter tracking is essential to close immunity gaps. Enhanced community engagement, early case detection, prompt isolation, risk communication, and strengthened preparedness, coordination, rapid response, and infection prevention measures are critical for reducing transmission and improving outbreak control.
Public health actions: Suspected measles cases were managed at health facilities, while infection prevention and control measures, risk communication, and community sensitisation activities were strengthened in affected sub-counties. The district implemented targeted vaccination and outreach services to improve coverage among unvaccinated and under-immunised children. Surveillance and outbreak response were enhanced through mentorship of health workers and activation of the District Task Force, which supported timely confirmation and response.
Conflict of interest: The authors declared no conflict of interest.
Author contribution: MDN conceptualised the study, led data collection and analysis, and drafted the article. SN and MM supported data analysis and technical review of the draft article. MDN and PE supported the revision of the first draft of the bulletin. MDN contributed to tool development, field coordination, and data quality assurance. RM and BKprovided technical input during the study design and data interpretation. All authors read and approved the final bulletin.
Acknowledgements: We appreciate the leadership and stewardship of the Amolatar District Local Government, as well as the active participation of the local community. Our gratitude also extends to the Ministry of Health, particularly the Uganda National Expanded Program for Immunisation (UNEPI), for their invaluable technical support.
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 republished. If cited as a reprint, it should be referenced in the original form.
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