A study1,2 written by Dr. Ju-Hyung Lee describes an experiment to investigate how airflow likely caused a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, the virus that causes the disease COVID-19) outbreak in a South Korean restaurant. Long before the COVID-19 pandemic, scientists worked to determine how far contaminated droplets can travel. Six feet is the social distancing standard for preventing droplet-borne illness. However, Dr. Lee’s team has shown contaminated droplets can travel much further, given the right situation. The researchers conducted airflow measurements, reviewed closed-circuit television footage, and interviewed people present at the time of the outbreak. See Figure 1 for a diagram of their investigation.
Confirmed case B was determined as already infected with SARS-CoV-2 when these individuals were dining in the restaurant. Due to the ventilation design, the direct airflow away from Confirmed case B infected at least three other people: Confirmed cases A, C, and D. The study indicated that a direct airflow with an air velocity of 1.0 meters/second (3.3 feet/second) was enough to infect someone 6.5 meters (21.4 feet) away, after only five minutes of exposure. Another person 4.8 meters (15.7 feet) away became infected after 21 minutes of exposure with an air velocity of 1.2 meters/second (3.9 feet/second). With the knowledge that infected droplets could travel farther than previously thought, Dr. Lee’s conclusion recommended “guidelines involving prevention, contact tracing, and quarantine for SARS-CoV-2 are required for control of this highly contagious disease.”
What does this mean for the public? When dining out, remember that social distancing six feet away may not be enough. Always consider using multiple means of exposure prevention when in public areas: cloth masks, face shields in combo with cloth masks, hand washing, ordering takeout/delivery, etc.
People can even participate in contact tracing programs. According to the Washington State Department of Health, Washington Exposure Notify3 is a tool that “works through smartphones, without sharing any personal information, to alert users if they may have been exposed.” This app does not keep personal information, and does not track where you go. It only exchanges Bluetooth coding to other app users. When a person tests positive, they update their app’s info and any phone you exchanged codes with within the last 14 days will receive a notification.
This is a contagious disease, so it is important to practice public health safety whenever possible. Never forget that safety is everyone’s responsibility.
- Journal of Korean Medical Science – :: JKMS :: Journal of Korean Medical Science
- LA Times – South Korea study shows how coronavirus spreads indoors – Los Angeles Times (latimes.com)
- WA Notify – WA Notify :: Washington State Department of Health