Coronavirus infection mechanism: Microdroplets infection
Introduction
The novel coronavirus disease 19 (COVID-19) has spread quickly throughout the world. It is highly contagious, causing an outbreak of respiratory illness in affected countries and even resulting in death. The WHO declared it a public health emergency of global proportions and concern (Adhikari et al., 2020). Although its characteristics and mechanisms of spread are not fully understood, there are two potential ways considered to explain transmission. One is an infection by coming into contact with something (someone) that has the virus on it, and the other is infection through droplets from coughing and sneezing. A third mechanism, experts say, is through microdroplets (NHK World report, 2020). This report explains how coronavirus microdroplets could linger in the air, the period they remain there, and how they spread coronavirus.
Coronavirus infection mechanism: Microdroplets infection
In this video, the research team in Japan conducts an experiment to study the potential transmission of severe acute respiratory syndrome coronavirus-2 via airborne microdroplets. Coronaviruses are small and can be carried in the air (Shereen, Khan, Kazmi, Bashir, & Siddique, 2020). It involves tracking the movement of particles in the air using laser beams and high sensitivity, high-definition cameras (Broom, 2020). Microdroplets are particles whose size is less than 100th of a millimeter. The technology can detect minute droplets as tiny as 0.1 micrometers wide (NHK World report, 2020).
It is already established that human to human transmission of the virus occurs as a result of close contact with an infected person, exposure to sneezing and coughing, respiratory droplets, and aerosols. Inhalation of the droplets carrying the virus facilitates penetration into the lungs and respiratory cells (Shereen, Khan, Kazmi, Bashir, & Siddique, 2020). The experiment tests the movement of the virus first via sneezing. Large droplets visible via the naked eye quickly fall. However, the high sensitivity camera shows tiny particles with a diameter of less than 10 micrometers that remain floating through the air. These particles are minute and light enough to linger and drift through the air as they ride the air currents (NHK World report, 2020). A single sneeze or cough, according to research estimates, could generate about 100,000 microdroplets (Broom, 2020).
The researchers ran the same experiment on a close-range conversation with people speaking loudly as an illustration of another source of microdroplets. It confirmed that when people talk, they emit these minuscule droplets (Broom, 2020). The loud conversation between two people generated many micro-droplets that remained in the air between them and did not drift away. Therefore, the people involved inhaled these droplets and their components from each other. These microdroplets carry many viruses, not just the SARS CoV-2 virus. Although it is uncertain what volume of micro-droplets leads to infection, micro-droplet transmission and infection may have occurred for COVID-19 and possibly other diseases. Heavy breathing may also generate microdroplets that linger in the air.
Sneeze and cough exposure, as well as a conversation within a reasonable distance, are therefore risk factors that can propagate the virus through microdroplet infection. The infection can spread from both symptomatic and asymptomatic people, which serves as another risk factor when one cannot identify who carries the virus (Singhal, 2020). These risks rationalize the directives on social distancing and wearing of face masks and other personal protective gear as a means to limit transmission (Broom, 2020). The risk increases in a closed, poorly ventilated space, as illustrated by the experiment on the video. To demonstrate the high risk in terms of the amount of time the virus can linger in the air, the lab simulated the movement of micro-droplets in an airtight room. If there were ten people in an enclosed space, the size of a classroom, and one person coughed, they spread about 100,000 droplets (NHK World report, 2020).
As in the previous experiment, the large droplets fall on the ground within one minute. However, the micro-droplets continued to drift. Twenty minutes later, these particles are still floating in the air and have spread throughout the entire enclosed space. The experiment shows that since the air currents are not moving, the micro-droplets do not move either. It is the flow of air that facilitates microdroplets’ movement as they cannot move on their own. Therefore, they stagnate and remain in place. However, if the air currents flow, the droplets would move along with them. The experiment shows that airflow carries away the floating, virus-harboring micro-droplets. The research advises having two openings to ventilate a room, perhaps one serving as an air inlet and the other an outlet which would allow airflow and increase its circulation. The flowing air can move the tiny, light micro-droplets, eliminating them from the space, and reducing the risk of transmission and infection (NHK World report, 2020).
Conclusion
The research presents a new way that explains how the coronavirus spreads. Micro-droplet infection is where tiny droplets in less than 10 micrometers in diameter linger in the air and can be inhaled, thus spreading disease. When an infected person sneezes, coughs, speaks (loudly), and breathes heavily, they generate these droplets. The big ones fall or settle on surfaces while the small particles float in the air. They can remain there for as long as 20 minutes in a poorly ventilated room. Movement of air currents sweeps the micro-droplets, moving them along and reducing the amount of time they linger in a given space.
References
Adhikari, S. P., Meng, S., Wu, Y.-J., Mao, Y.-P., Ye, R.-X., Wang, Q.-Z., . . . Zhou, H. (2020). Epidemiology, causes, clinical manifestation and diagnosis, prevention, and control of coronavirus disease (COVID-19) during the early outbreak period: a scoping review. Infectious Diseases of Poverty, 1-12. doi:https://doi.org/10.1186/s40249-020-00646-x
Douglas Broom. (2020, April). This Japanese experiment shows how easily coronavirus can spread – and what you can do about it. Retrieved from World Economic Forum: https://www.weforum.org/agenda/2020/04/coronavirus-microdroplets-talking-breathing-spread-covid-19/
NHK World report. (2020, April). SARS- CoV-2 Coronavirus Microdroplets. NHK World report. Japan: YouTube. Retrieved from https://www.youtube.com/watch?v=vBvFkQizTT4&t=12s
Shereen, M. A., Khan, S., Kazmi, A., Bashir, N., & Siddique, R. (2020). COVID-19 infection: Origin, transmission, and characteristics of human coronaviruses. Journal of Advanced Research, 91-98. doi:10.1016/j.jare.2020.03.005
Singhal, T. (2020). A Review of Coronavirus Disease-2019 (COVID-19). Indian Journal of Pediatrics, 281-286. doi:10.1007/s12098-020-03263-6