[Reading Science] Droplet Infection and Cough Etiquette

The corridor of Wuhan Red Cross Hospital crowded with patients wearing masks. With so many people like that, I am worried that infections might actually occur within the hospital. I hope a vaccine is developed as soon as possible.
[Photo by Wuhan AFP/Yonhap News]

[Asia Economy Reporter Kim Jong-hwa] As the 'Novel Coronavirus Infection (Wuhan Pneumonia)' continues to spread, the global community is on high alert. First reported on December 12 last year as an acute respiratory syndrome, the spread has not stopped due to the absence of a developed vaccine.

Since it is a newly emerged disease and spreads rapidly, the disease's name had not been decided until early this year. This disease is known as an acute pneumonia of unknown cause that originated in Wuhan, China, during the early outbreak, and is thus referred to as 'Wuhan Pneumonia' among other names. The English version of Wikipedia uses the term 'Wuhan coronavirus.'

Our government uses the term 'Novel Coronavirus Infection.' The temporary name for the pathogen designated by the World Health Organization (WHO) is '2019-nCoV (2019 Novel Coronavirus).' Our government follows the WHO's designated name as is.

Since 2015, WHO has recommended avoiding the use of geographic locations in disease names to prevent 'stigmatization.' Therefore, it is preferable not to use the place name 'Wuhan.' Instead of 'Wuhan Pneumonia,' it is more appropriate to use the term 'Novel Coronavirus Infection,' or simply 'Novel Coronavirus,' as used by our government.

The novel coronavirus spreads through 'droplet infection (飛沫感染).' Droplet infection occurs when an infected person coughs or sneezes, releasing small droplets containing viruses or bacteria that enter another person's mouth or nose, causing infection. Typically, the size of these droplets is 5 micrometers (μm, where 1 μm is one-millionth of a meter) or larger.

Generally, a single cough releases about 3,000 droplets within 2 meters in front of the person. Although the number of droplets is around this amount, the number of bacteria within these droplets is more concerning. According to one study, a single cough can release approximately 100,000 bacteria that can travel roughly 7.7 meters. Sneezing is even more powerful; about 40,000 droplets can travel at speeds exceeding 300 km/h.

A scene from the cough etiquette song "Neol Mannareo Ganeungil," produced by the Korea Disease Control and Prevention Agency together with singer Min Kyung-hoon to promote cough etiquette. It conveys the message that you should cover your mouth and nose with your sleeve when coughing.
[Photo by YouTube screen capture]

To avoid droplet infection, it is concluded that one should stay at least 2 meters away from an infected person. However, this is impossible in daily life where infected individuals are not identifiable. Moreover, when air conditioners or similar devices draw in viruses and then release them back into the air, droplets and bacteria can spread much farther, making distance from the infected person less meaningful.

The preventive measure against this is wearing masks. Since many masks have recently been developed to block fine dust, using masks designed for fine dust can also prevent infection. But what should one do when not wearing a mask?

Currently, a 'cough etiquette' campaign is underway, encouraging people to cover their mouth and nose with their sleeves when coughing or sneezing. Usually, people cover their mouth with their hands, but this can transfer bacteria from droplets onto the hands, which can then spread to others through handshakes, door handles, or public items.

When there is no time to take out a handkerchief or tissue, it is advised to cover the mouth and nose with the sleeve. However, there are opposing views on this cough etiquette campaign. Dr. Peter Lin, a renowned virus researcher from Canada, stated in an interview with a broadcaster, "Coughing or sneezing into sleeves covered with countless bacteria means inhaling bacteria stuck on the sleeve," and added, "I don't know the basis for such a belief."

Dr. Lin's argument has some merit. However, if a certain distance is maintained from the sleeve, inhaling bacteria is unlikely. A domestic expert responded positively to the cough etiquette, saying, "The sleeve is the least likely to infect others." In this regard, the cough etiquette campaign led by the Korea Centers for Disease Control and Prevention is considered reasonably effective.

Coronavirus primarily spreads through droplet infection. It is common for droplets expelled by an infected person's cough or sneeze to land on surfaces, survive there, and then be transmitted when another person touches those surfaces. Viruses survive longer on hard surfaces like metal or plastic, while their survival time is much shorter on soft surfaces like fabric.

Cough etiquette promoted by the Korea Disease Control and Prevention Agency to prevent droplet infection.
[Photo by Korea Disease Control and Prevention Agency website]

The reason for wearing masks or following cough etiquette is not only to protect oneself but fundamentally to prevent infecting others. Masks worn by infected individuals prevent saliva from splashing onto others' faces, masks worn by uninfected individuals block droplets from directly entering the respiratory tract, and masks also prevent hands contaminated with bacteria from directly touching the mouth or nose.

The cleanest method is to use tissues. After covering a cough or sneeze with a tissue, it should be immediately disposed of in a trash bin. Regardless of the efficiency of Korea's cough etiquette, Dr. Lin emphasized, "Be careful of the floor." He warned, "Viruses are abundant on streets, bus floors, and office floors, so carelessly placing bags on the floor can be fatal."

The most important preventive action against disease is always handwashing. Washing hands with soap under running water for more than 30 seconds is the foundation of all disease prevention. Cleaning the hands, which are used most frequently, is the top priority because droplet infection often starts when hands touch the mouth or nose.

The best way to overcome the novel coronavirus is to get vaccinated. However, since a vaccine has not yet been developed, avoiding infection is essential. Washing hands frequently and following cough etiquette are ways to protect yourself, your family, and your colleagues' health.