An investigation of COVID-1 9 outbreak in a superstore at Chiangmai province, October - November 2021

Abstract

Introduction: In October 2021, the Office of Disease Prevention and Control 1 (ODPC 1) in Chiangmai province was alerted by the Chiangmai Provincial Public Health Office (CMPPHO) about a COVID-19 outbreak at a superstore A. The ODPC 1 and CMPPHO investigation joint team aimed to confirm diagnoses and verify the outbreak, describe case characteristics, identify associated factors, and suggest control measures of COVID-19 outbreak.

Methods: A cross-sectional analytical study was conducted for active case finding and the COVID-19 vaccine database of the Ministry of Public Health were reviewed. Confirmed cases were employees of Store A who tested positive for SARS-CoV-2 between October 6 and November 28, 2021. Studies were including environmental survey, analytical study and related risk. Data were analyzed using frequency statistics, percentages, and multiple logistic regression for associated factor analysis.

Results: We identified 48 confirmed cases from 374 employees (12.8%) and a male-to-female infection ratio was 1:1.5. The median age was 29 years. The index case emerged on October 6 in a hardware store employee who had attended a social alcohol drinking together then spread to nearby shops, leading to its closure for cleaning from October 20-22. Subsequently, employees were quarantined for 14 days. No additional infected person was found since November 1. Multiple logistic regression indicated partial vaccination (Adjusted OR = 0.22, 95%CI 0.06-0.77, p<0.05) and occasional handwashing (Adjusted OR 0.19, 95%CI 0.05-0.76, p<0.05) as protective factors, while having infected family members was a significant risk factor (Adjusted OR = 16.57, 95%CI 2.87- 95.76, p<0.05)

Conclusion: The outbreak started in a hardware store and expanded to other sectors within superstore A. Household infections were a risk factor, while vaccination and handwashing served as protective factors. Recommendations include symptom monitoring, ATK testing for symptomatic individuals, promoting vaccination, and implementing COVID-19 prevention guidelines in superstores.