Investigation of a COVID-19 Cluster in a Football Academy of Buri Ram, October 2021

A COVID-19 cluster in a football academy, Buri Ram, Thailand, was notified in October 2021. We aimed to characterize the outbreak, identify the source of disease and risk factors for infection, and give recommendations for preventive measures. We conducted a descriptive study by interviewing cases and academy participants, and assessed ventilation measures at the academy via an environmental survey. We performed a retrospective cohort study among football players using Poisson regression to identify risk factors of COVID-19 infection presenting adjusted incidence rate ratios (AIRR) and 95% confidence intervals (CI). The attack rate was 22.4% (48/214). The median age was 14 years and 77.1% of patients had mild illnesses. All examined environmental surfaces tested negative for SARS-CoV-2. The bedroom density had a strong relationship with attack rates among female bedrooms. Risk factors for infection were being high-risk close contact with the primary case (AIRR 5.4, 95% CI 2.2–12.9) and sleeping in crowded bedrooms (AIRR 2.42, 95% CI 1.14–5.15). Mask-wearing was a protective factor (AIRR 0.32, 95% CI 0.13–0.80). We recommend sports academies and schools encourage mask-wearing during an outbreak, provide living areas that conform to recommended density guidelines, and prepare an isolation or quarantine room for infected students.