Investigation of a COVID-19 Outbreak at a Military Training Unit Mueang Ubon Ratchathani District, Ubon Ratchathani Province, May 2025

Abstract

Background: The ongoing COVID-19 pandemic necessitates rapid and effective outbreak responses to suppress disease transmission and minimize multi-dimensional impacts. This study investigated a COVID-19 cluster among military recruits at a training facility in Mueang Ubon Ratchathani District, Ubon Ratchathani Province. The primary objectives were to confirm the outbreak, review diagnostic criteria, characterize epidemiological features, trace cases and sources of infection, identify risk factors, and establish targeted containment and prevention measures.

Methods: A retrospective analytical epidemiological study was conducted among N = 164 military personnel at the facility, comprising n = 127 cases and n = 37 non-cases. Data were extracted using standardized outbreak investigation forms. Statistical analyses were performed using descriptive statistics alongside modified Poisson regression to estimate adjusted risk ratios (aRR) with 95% confidence intervals (95% CI), setting the threshold for statistical significance at p < 0.05.

Results: The attack rate reached 77.44% (127/164). Diagnostics identified 123 probable cases via Rapid Antigen Tests (ATK) and 5 laboratory-confirmed cases via RT-PCR. Regular hand hygiene served as a significant protective factor, substantially lowering infection risk (aRR = 0.38, 95% CI: 0.18–0.82, p = 0.012). Conversely, face mask usage was associated with an elevated risk of infection (aRR = 1.35, 95% CI: 1.02–1.78, p = 0.034), a phenomenon likely attributable to reverse causality, wherein individuals initiated mask-wearing reactively following symptom onset. Other exposure parameters—including close contact proximity, sharing of personal items, and communal bathing practices—demonstrated no statistically significant association with transmission risk between cases and non-cases.

Recommendations: Outbreak management within high-density environments should prioritize personal hygiene practices—specifically routine handwashing—complemented by environmental sanitation enhancements and accelerated COVID-19 vaccination coverage for new recruits and personnel in high-risk zones to ensure robust containment and prevention in future scenarios.