Measles outbreak propagated by poor isolation practices in schools and health facilities, Mityana District, Uganda, March–August 2025

Summary

Background: In April 2025, Mityana District in Central Uganda confirmed a measles outbreak. We investigated to determine the outbreak’s magnitude, identify risk factors for transmission, assess vaccine coverage (VC), and provide evidence-based recommendations to prevent future outbreaks.
Methods: We defined a suspected case as acute fever and maculopapular rash with cough, coryza, or conjunctivitis in a Mityana resident from March to August 2025; a confirmed case was a suspected case who was IgM-positive for measles. We found cases through health facility records review and community case search using a house-to-house approach and snowballing and developed a line list. We conducted a matched case-control study to identify factors associated with measles transmission. We estimated VC as the proportion of vaccinated controls. We conducted environmental assessments in health facilities, households, and schools to evaluate patient flow, isolation practices, and levels of crowding that could facilitate disease transmission.
Results: We identified 100 case-patients. Median age was 3 years (IQR: 1-5 years). The earliest case-patient was a 12-months old male from Kiboga District with a reported on-going measles outbreak. Receipt of MR was protective (aOR 0.24, 95% CI: 0.095-0.53), while attending school (aOR 4.0, 95% CI: 1.2-12) and visiting a health facility 3 weeks before onset (aOR=2.6, 95% CI=1.2-5.7) were risk factors. The VC was 84% (95% CI=74-91). Environmental assessment revealed overcrowding in schools and lack of isolation at health facilities.
Conclusions: The outbreak was likely introduced from a neighboring district, Kiboga and driven by low vaccination coverage. These were exacerbated by transmission in schools and nosocomial transmission at health facilities. We recommended mass immunization campaigns targeting children, strengthening triage and isolation in schools and health facilities, and intensified community sensitization on early recognition and isolation of measles cases. Following implementation of these interventions, the number of reported cases progressively declined.

Background

Measles is a highly infectious vaccine-preventable disease caused by measles virus. It is transmitted via droplets from the nose, mouth, or throat of infected persons. Measles presents with high-grade fever, maculopapular rash, cough, coryza and conjunctivitis. The rash develops 14 (range: 7-21) days after exposure, starting on the face and upper neck and gradually spreading downwards. Patients are infectious starting approximately four days before to four days after rash onset (1). Measles infection can result in severe complications including diarrhea, pneumonia, encephalitis, and vision loss, with pneumonia being the leading cause of measles-related deaths. These complications contribute to high morbidity and mortality, particularly in sub-Saharan Africa, where malnutrition, limited healthcare access, and gaps in vaccination coverage amplify the disease burden (2-5).

Vaccination remains one of the most effective strategies for preventing measles and limiting its transmission. Globally, measles vaccination is estimated to have saved approximately 60 million deaths between 2000 and 2023 (6). To achieve herd immunity and prevent outbreaks, the WHO recommends a vaccine coverage (VC) of at least 95% for any antigen (7). Globally, the coverage is below the WHO recommendation with approximately 83% of children had received the first dose of the measles-containing vaccine (MCV1).

In Uganda, the national immunization program provides two doses of the measles-rubella (MR) vaccine, as recommended by WHO (8). The first dose (MR1), is administered at 9 months, while the second dose (MR2) is given at 18 months. Despite these efforts, Uganda’s vaccination coverage remains suboptimal with MR1 coverage at 96% and MR2 at only 52% as of the first quarter of the 2024/2025 financial year (MoH DHIS2 data). Consequently, Uganda continues to experience recurrent measles outbreaks, reflecting persistent immunity gaps. From January to August 17, 2025, 53 districts had been confirmed to have measles outbreaks according to the Uganda National Expanded Program on Immunization (UNEPI) report. On 19th April 2025, Mityana District confirmed a measles outbreak after suspected measles cases were admitted at Mityana General Hospital. We investigated the outbreak to determine its scope, assess risk factors for disease transmission, assess vaccine coverage and recommend evidenced-based interventions.

Methods

The investigation was conducted in Mityana District where MR vaccination coverage was 88% before the outbreak (DHIS2, June 2025). We defined a suspected measles case as acute onset of fever and maculopapular rash and any of the following symptoms: cough, coryza, and conjunctivitis in a resident of Mityana District from March 1^st to 30^th August, 2025. A confirmed case was a suspected case that tested positive for IgM measles-specific antibodies.

We conducted active case search in both health facilities and communities. In health facilities, we reviewed health records including out-patient department (OPD) and in-patient department (IPD) registers.  In the communities, with the help of village health teams (VHTs) and health assistants, we conducted house to house search and also found cases through snowballing.

We calculated attack rates (AR) by age, sex, and sub-county using population denominators obtained from the Uganda Bureau of Statistics 2024 for Mityana District. We constructed choropleth maps using QGIS software to describe the ARs by sub-county for Mityana District. We conducted an environmental assessment in the pediatric ward, focusing on patient flow and isolation practices. In addition, we inspected households and schools in the outbreak area to assess levels of crowding.

To identify factors associated with infection, we conducted an age-matched case-control study among children aged ≤14 years residing in the two most affected divisions, Ttamu and Busimbi. Controls were selected from the same villages as cases and had no history of fever or rash during the outbreak period. Vaccination status was verified using vaccination cards where available or caretaker recall when both the vaccination date and site could be accurately reported. VC for MR1 was estimated as the percentage of controls aged ≥9 months who had received the MR vaccine, by age groups (9-17 months, 18-59 months, and 5-14 years), assuming that the controls were representative of the general population.

This outbreak investigation was conducted as part of a public health emergency response and was classified as non-research/public health practice by the Uganda Ministry of Health and the US CDC. The investigation was approved by the US CDC in accordance with applicable federal laws, CDC policy, and the Declaration of Helsinki. Written informed consent was obtained from participants aged 18 years and above, while parental/guardian consent and participant assent were obtained for individuals below 18 years.

Results

Descriptive epidemiology

We interviewed 100 case-patients, of which five were confirmed, 95 were suspected, and one died. Of the 100 cases, 6 (6%) were aged <8 months, 11 (11%) were 9-17 months, 48 (48%) were aged 18-59 months, and 35 (35%) were aged between 5 and 14 years. Median age was 3 years (IQR: 1-5 years). Children aged 9-17 months (AR=11/10,000) and those aged 18-59 months (AR=10/10,000) were the most affected. Males and females were equally affected. Vaccination status was assessed using vaccination cards for 47% (47) of the case-patients. Overall, 7% (7) of all case-patients had received both MR vaccine doses.  Regarding education status, 62% (62) were attending school. Most case-patients 95% (95) were not isolated during illness, while 24% (24) were admitted to hospital. Additionally, 29% (29) of the case-patients came from households that had other case-patients.

Six out of the 13 (46%) sub-counties in Mityana District were affected with measles infection with Ttamu (77/10,000) and Busimbi (60/10,000) divisions being most affected (Figure 1). According to DHIS2 data, Ttamu and Busimbi had a lower MR1 coverage of 55% and 60% respectively compared to the recommended MR coverage of 95% (9).

On 7^th March, 2025, case A, a 12-month-old male from Kiboga District, sought care at Mityana General Hospital. A few days later, more measles cases were suspected at the hospital. Between May 1-9, a selective vaccination campaign was conducted targeting children who had missed any of the MR doses. However, the campaign was limited to only three divisions and achieved just 24% coverage, which was insufficient to break the transmission as cases continued to rise. Consequently, the National Rapid Response Team (NRRT) was deployed to Mityana from July 28 to August 7, 2025, to investigate the outbreak. We recommended a non-selection vaccination campaign which was conducted between 22^nd August to 1^st September.

Environmental assessment findings: At Mityana General Hospital, we observed that children with suspected or confirmed measles were not separated from other patients in OPD. In the pediatric ward, measles cases were admitted in the same space as non-measles patients, resulting in mixing of infected and uninfected children. Similarly, in schools, children with measles were not isolated from their classmates, which could have propagated the measles transmission in schools.

Case-Control study findings: In multivariable analysis (Table 1) factors significantly associated with measles infection were; having received one dose of MR1 (aOR=0.24, 95%CI=0.095-0.53), attending school (aOR 4.0, 95%CI 1.2-12), and having visited a health facility three weeks prior to onset of symptoms (aOR=2.6, 95%CI=1.2-5.7).

Table 1: Factors associated with measles infection in Mityana District, March–August 2025

Vaccine coverage

Overall, among children aged 9 months to 14 years, coverage was 84% (95% CI=74-91).

Discussions

The measles outbreak in Mityana District was propagated by non-vaccination for measles, exposure to a measles case-patient in schools and in health facilities and most likely originated as a spillover from the neighboring Kiboga District, which had been experiencing an ongoing outbreak since February 2025.

Children aged 9-17 months were affected the most, highlighting the vulnerability among children who are due for the second MR vaccine. In Mityana, this vulnerability was likely exacerbated by a low MR coverage. These findings are similar with investigations in Nakaseke and Kakumiro districts (10, 11).

School attendance increased odds of having a measles infection by four times, with clusters emerging in MF Primary School. Schools are recognized amplifiers of measles outbreaks due to crowding, prolonged indoor exposure, and challenges in implementing isolation measures. Similarly, children who visited health facilities within three weeks prior to symptom onset were 2.6 times more likely to get a measles infection than those who did not. Similar findings were documented in Lyantonde District (11) and in Moroto District (12). In Mityana, absence of triage systems and lack of isolation rooms likely created opportunities for transmission in health facilities.

Study limitations: Some exposures such as attendance at social gatherings and contact with suspected cases relied on self-reported data, which is subject to reporting bias and, not all suspected cases were laboratory-confirmed; thus, some misclassification of rash illnesses as measles cannot be ruled out.

Conclusion: The measles outbreak in Mityana District resulted from cross-district importation and was sustained by low vaccination coverage. Transmission was amplified in schools and health facilities due to overcrowding and inadequate isolation.

Public health actions: Mityana District conducted a non-selective mass vaccination campaign targeting all eligible children across the 13 sub-counties. Additionally, the pediatric ward at Mityana General Hospital established a dedicated isolation unit for children presenting with measles symptoms. This intervention was critical in reducing nosocomial transmission by separating suspected measles cases from other pediatric patients. Health workers were oriented on infection prevention and control measures, including triage of febrile rash illnesses, use of personal protective equipment, and early referral of suspected cases.

Recommendations: Strengthening routine immunization with emphasis on timely completion of the two-dose MR schedule, improving triage and isolation in schools and health facilities, and enhancing cross-district surveillance and coordination are critical to preventing similar measles outbreaks in the future.

Acknowledgements: We acknowledge the Ministry of Health under Uganda expanded program on immunization (UNEPI), Uganda Public Health Fellowship Program for the technical oversight and funds and the District Health Team of Mityana for the support and work done during this investigation.

Author contributions: MN conceptualized the study idea, collected data, analyzed it, and wrote the bulletin. NM, JW, RM, YN conceptualized the study idea, collected data and reviewed the bulletin. YN RM, and BK supported in editing, and reviewing of the bulletin.

Conflict of interest: The authors declare no conflict of interest

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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