Study population and setting
The aim of this study was to investigate an outbreak of COVID-19 among 3,635 employees of a meat processing facility in South Dakota during the first wave of the COVID-19 pandemic in the United States. Following notification of a case of COVID-19 among employees at the facility on March 24 2020, the South Dakota Department of Health (SDDOH) led an investigation to isolate the case, and identify and quarantine contacts. A contact was defined as a person within 6 feet of the COVID-19 case for ≥ 5 minutes during the infectious period, i.e., between start of symptoms and end of isolation. On April 1, the definition of a contact was expanded to include the 48 hours before symptom onset. By April 2, 19 cases were confirmed, and enhanced testing was put in place such that any employee with signs & symptoms of COVID-19 could get a test from a local health facility. The following additional measures were also implemented: employee screening, physical barriers installed on production lines, and masks were made optional. By April 11, 369 cases were confirmed, and a phased closure of the facility began. From April 12-14, no more animals were slaughtered, only already slaughtered meat was processed for shipping, and the facility began closing departments. From April 13, masks became mandatory. From April 15, only staff responsible for maintenance, cleaning & sanitization, transportation of remaining meat, and implementation of COVID-19 prevention protocols reported to work. A case was defined as a reverse transcription–polymerase chain reaction (RT-PCR) positive test in a symptomatic individual, or a positive test in an asymptomatic person up to 2 weeks after the phased closure which began on April 12. Employees who did not work during this period of March 2 to April 25 were excluded from the analysis.
Summary of Main Findings
The facility had 3,635 employees who harvested and processed animals from March 2 to April 25, 2020. In total, 25.6% (929) of employees, and 8.7% (210 out of 2,403) of their contacts outside of work were diagnosed with COVID-19. Within the two counties where the facility is located, a total of 2,199 COVID-19 cases were identified during this period, and facility employees made up almost 42% of these cases. Median age of persons with COVID-19 was 42 years among employees, and 29 years among contacts. Overall, 4.2% of employees with COVID-19 were hospitalized (median age, 60 years), and 4.3% of contacts with COVID-19 were hospitalized (median age, 64 years). Two employees died. In the first 3 weeks of the outbreak, the proportion with COVID-19 increased 5-fold (week 1 = 0.2%, week 2 = 1.2%, and week 3 = 6.8%). There were an average of 67 cases per day in week 4, which declined to 10 cases per day within 7 days of facility closure.
Use of an RT-PCR positive test to confirm COVID-19 infection.
Enhanced testing among facility workers likely led to more case detection among employees than among contacts or community members. Given that most employees were tested for COVID-19 following onset of symptoms, the proportions in the study are likely to be underestimates of the true proportion with COVID-19 among facility employees and their contacts.
This study demonstrates the potential of COVID-19 to spread rapidly in settings where individuals are in close proximity to one another, and for extended periods. It additionally illustrates the importance of enacting COVID-19 control measures before and immediately after introduction of COVID-19 within a workplace setting.
This review was posted on: 27 August 2020