J Korean Med Sci.  2020 Dec;35(46):e415. 10.3346/jkms.2020.35.e415.

Evidence of Long-Distance Droplet Transmission of SARS-CoV-2 by Direct Air Flow in a Restaurant in Korea

Affiliations
  • 1Department of Preventive Medicine, Jeonbuk National University Medical School, Jeonju, Korea
  • 2Jeonbuk Center for Infectious Disease Control and Prevention, Jeonju, Korea
  • 3Korea Disease Control and Prevention Agency, Cheongju, Korea
  • 4Division of Health Care, Jeonbuk Provincial Government, Jeonju, Korea
  • 5Department of Aerospace Engineering, College of Engineering, Jeonbuk National University, Jeonju, Korea

Abstract

Background
The transmission mode of severe acute respiratory syndrome coronavirus 2 is primarily known as droplet transmission. However, a recent argument has emerged about the possibility of airborne transmission. On June 17, there was a coronavirus disease 2019 (COVID-19) outbreak in Korea associated with long distance droplet transmission.
Methods
The epidemiological investigation was implemented based on personal interviews and data collection on closed-circuit television images, and cell phone location data. The epidemic investigation support system developed by the Korea Disease Control and Prevention Agency was used for contact tracing. At the restaurant considered the site of exposure, air flow direction and velocity, distances between cases, and movement of visitors were investigated.
Results
A total of 3 cases were identified in this outbreak, and maximum air flow velocity of 1.2 m/s was measured between the infector and infectee in a restaurant equipped with ceiling-type air conditioners. The index case was infected at a 6.5 m away from the infector and 5 minutes exposure without any direct or indirect contact.
Conclusion
Droplet transmission can occur at a distance greater than 2 m if there is direct air flow from an infected person. Therefore, updated guidelines involving prevention, contact tracing, and quarantine for COVID-19 are required for control of this highly contagious disease.

Keyword

Infectious Disease Transmission; SARS-CoV-2; COVID-19

Figure

  • Fig. 1 The asymptomatic period and symptom onset of all three coronavirus disease 2019 cases.

  • Fig. 2 Timeline of coronavirus disease 2019 infector and infectees in the restaurant. Case A (index case) overlaps about 5 minutes (17:15–17:20) with case B (infector), who overlaps case C for about 21 minutes (17:22–17:43).

  • Fig. 3 Schematic diagram of the outbreak restaurant equipped with ceiling-type air conditioners. The arrowed solid streamlines represent the air flow directions in the restaurant. Curved air streamlines represent that air streams from the ceiling air conditioners are reflected from the wall or barrier, and move downward toward the floor.


Cited by  1 articles

Frequent Occurrence of SARS-CoV-2 Transmission among Non-close Contacts Exposed to COVID-19 Patients
Jiwon Jung, Jungmin Lee, Eunju Kim, Songhee Namgung, Younjin Kim, Mina Yun, Young-Ju Lim, Eun Ok Kim, Seongman Bae, Mi-Na Kim, Sun-Mi Lee, Man-Seong Park, Sung-Han Kim
J Korean Med Sci. 2021;36(33):e233.    doi: 10.3346/jkms.2021.36.e233.


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