Investigation of the 2024 Aeromonas hydrophila outbreak in Jinja and Luuka, Uganda: A mixed-methods approach

Abstract

Introduction: Aeromonas infections are an emerging global public health challenge due to their complex pathogenicity and diverse virulence factors. These infections can lead to various conditions in humans, such as gastroenteritis, wound infections, and septicaemia. On February 12, 2024, an outbreak of Aeromonas hydrophila infection in Jinja and Luuka, Uganda, resulted in cases of abdominal pain, diarrhoea, vomiting, and death. This study described the epidemiology of the outbreak and the public health response. Methods: To investigate the outbreak and evaluate the epidemiology and public health response, a mixed-methods study was conducted using secondary data involving 185 individuals. Confirmed cases were identified through positive culture results from gastric aspirates or stool samples. Suspected and probable cases were defined by at least two symptoms, including abdominal pain, vomiting, and diarrhoea, history of exposure, and an epidemiological link to a confirmed case or outbreak cluster occurring between February 12 and 27, 2024. The study also included secondary laboratory investigations, food safety assessments, and an evaluation of timeliness using the 7-1-7 metric. Data analysis was performed using STATA-17. Results: Among 185 individuals investigated, 54.1% were female, the mean age was 23.9 ±18.7years, 103 Aeromonas hydrophila cases were identified, resulting in an attack rate of 55.7%(103/185), including one laboratory-confirmed case. Cases were younger than non-cases (22.1 vs. 26.3 years). The outbreak lasted five days (12–16 February 2024), peaked on 14 February, and had an incubation period of 33–38 hours, indicating a common-source exposure. Eight deaths occurred (case fatality rate: 7.8%). Geographical clustering of cases was observed, with high attack rates in Iziru (48%) and Bugomba (78%) parishes, respectively. Funeral food exposure showed an attributable risk of 9.3/100 and an attributable fraction of 15.7%. A. hydrophila was detected in gastric aspirate and water samples, implicating contaminated water and ill food handlers. Relapse occurred in 30.1% of cases. Conclusion: The outbreak of Aeromonas hydrophila was rapid, geographically clustered, and linked to contaminated water and ill food handlers, with funeral food exposure contributing to the outbreak. High attack, relapse, and fatality rates highlight the need for timely water safety interventions, improved food hygiene, and strengthened outbreak detection and response to prevent future occurrences.