Investigation of a Cluster of COVID-19 among Factory X Workers, Buikwe District, Uganda, 2020

ABSTRACT

Introduction/ Background: In September 2020, a cluster of SARS-COV-2 infections was reported among workers at a factory in Uganda. The factory had already introduced COVID-19 risk reduction measures for all employees, including face mask use. We investigated the cluster to determine exposures associated with transmission and inform evidence-based control measures. Methods: We defined a case as positive RT-PCR test for SARSCOV- 2 in a Factory X worker during August- September 2020. We conducted a case-control study using a randomly selected subset of case patients. A control was a Factory X worker with a negative RTPCR test for COVID-19 during August-September 2020, selected randomly from Factory X departments with cases. Case-patients and controls were interviewed using a standardized questionnaire, asked about possible exposures. We analysed data using logistic regression to obtain an adjusted odds ratio (AOR) with confidence interval (CI). We interviewed facility staff on preventive measures and conducted an observational assessment for ventilation and crowding. Results: Among 163 case-patients (factory attack rate=11%), none died. The index case-patient was a 27-year-old employee with infection confirmation on August 10. In the case-control study with 75 cases and 75 controls, lack of self-reported mask use (AOR=14, 95% CI 2.4-76), and working in the engineering (AOR=5.9, 95% CI 2.3-16) or old garments (AOR=2.4. 95% CI 1.1- 5.5) departments were associated with infection. Engineering and old garments departments lacked windows, while other departments all had open windows. We observed workers on production lines spaced closely together. Impact Based on the findings, Integration of tracking mechanisms for local infections at workplaces and enhanced focus on preventive measures, including periodic worker monitoring to ensure adherence to preventive measures, may be warranted during higher-risk times to prevent such outbreaks in the future. Conclusion: This SARS-COV-2 cluster was associated with inadequate mask use and poor ventilation, likely exacerbated by congestion. We recommended enforcement of factory risk reduction measures including mask use, increased spacing on production lines and provision of adequate windows and doors in all departments.