COVID-19 Outbreak in a Call Center, South Korea.

COVID-19 Outbreak in a Call Center, South Korea. Spencer EA, Heneghan C.

https://www.cebm.net/study/covid-19-outbreak-in-a-call-center-south-korea/

Published on June 30, 2020

Reference Park SY, Kim YM, Yi S, Lee S, Na BJ, Kim CB, et al. Coronavirus disease outbreak in call center, South Korea. Emerg Infect Dis. 2020 Aug. 2020
Study type
Country South Korea
Setting Workplace: call centre
Funding Details
Transmission mode Person to person, Close contact
Exposures Office work

Bottom Line

High attack rates were identified for workers in an office space.  A map of the workspace and cases demonstrates the likelihood of close working contact increasing risk.

Evidence Summary

1,143 out of 1,145 (99.8%) persons under investigation were tested for COVID-19 (922 employees, 201 residents, and 20 visitors): 97 (8.5%) confirmed cases were identified, indicating an attack rate of 8.5%.

Restricting the analysis to just the workers on one high-prevalence floor, the attack rate was around 44%.

Source: Volume 26, Number 8—August 2020 – Emerging Infectious Diseases journal – CDC https://wwwnc.cdc.gov/eid/article/26/8/20-1274-f2

What did they do?

This study described the epidemiology of a COVID-19 outbreak in a call centre in South Korea. 

The authors identified and investigated 922 employees who worked in commercial offices in a specified building, as well as 203 residents who lived in the residential apartments, and 20 visitors to the building.

The call centre is located on the 7th, 8th, 9th floors and the 11th floor of the building; with a total of 811 employees. Employees do not generally go between floors, and they do not have an in-house restaurant for meals.

Information was collected on demographic characteristics and presence of symptoms using face-to-face interviews using standardized questionnaires. 

The building was closed on 9th March 2020, immediately after the outbreak was reported. 

The study authors offered testing to all occupants (office workers and apartment residents) during March 9th to 12th. Nasopharyngeal and oropharyngeal swab specimens from PUIs for immediate real-time reverse transcription PCR testing were collected; the average turnaround time was 12 to 24 hours.  Confirmed case-patients were isolated, and negative case-patients were mandated to stay quarantined for 14 days.  All test-negative case-patients were followed and re-tested until the end of quarantine. 

Also investigated, tested, and monitored were the household contacts of all confirmed case-patients for 14 days after discovery, regardless of symptoms.  People tracked via cell phone data to having been present close to the building were messaged by SMS and instructed to avoid contact with others and get tested. The frequencies and proportions for categorical variables were reported. 

Study reliability

It is hard to know what features of this study are representative of the wider community.
The methods of observation were comprehensive with complete 14-day follow-up of close contacts of case-patients after containment measures were implemented.

These cases could not be tracked to another cluster, making it difficult to identify the actual index case-patient. Not all clinical information was available for all confirmed cases, prohibiting detailed description of clinical syndromes.

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes Yes Yes Yes Unclear

What else should I consider?

Extensive contact tracing, testing contacts, and early quarantine blocked further transmission and might be an effective strategy for outbreaks in crowded work settings.

About the authors

Carl Heneghan

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings

Elizabeth Spencer

Elizabeth Spencer

Dr Elizabeth Spencer; MMedSci, PhD. Epidemiologist, Nuffield Department for Primary Care Health Sciences, University of Oxford.