- Evidence of SARS-CoV-2 spreading via airborne transmission is growing
- Health professionals emphasise the need for face masks to reduce airborne transmission
- WHO's recommendation for physical distancing may be insufficient
Masks have become the world’s latest weapon against the new coronavirus which has infected more than 6.1 million people worldwide so far and killed 372 136, as of 1 June, stats by the Johns Hopkins Coronavirus Resource Centre indicate.
And since evidence of aerosol transmission of the virus in asymptomatic people is constantly surfacing, researchers, whose work was published in Science last month, suggest that this only proves the importance of regular widespread testing, mask-wearing and physical distancing.
WHO recommendation may not be sufficient
Public places in the world, including shopping centres, restaurants, and schools, have been following the World Health Organization’s (WHO) guidelines regarding physical distancing. According to WHO:
“Maintain at least 1m (3ft) distance between yourself and others. Why? When someone coughs, sneezes, or speaks, they spray small droplets from their nose or mouth which may contain the virus.
“If you are too close, you can breathe in the droplets, including the Covid-19 virus if the person has the disease.”
So far it is known that Covid-19 virus, named SARS-CoV-2, can be transmitted in at least two ways, either when an infected individual coughs or sneezes: by coming in close contact with infected individuals, or by touching contaminated surfaces and objects such as doorknobs and tables.
However, growing numbers of studies are showing that the virus can also be transmitted through aerosols, and that these aerosols can travel certain distances.
In their published paper, the three researchers explain that more recent measurements indicate that: “intense coughs and sneezes that propel larger droplets more than 20ft [6m] can also create thousands of aerosols that can travel even further”, and that WHO’s recommendations are therefore not sufficient, especially indoors where aerosols can stay airborne for hours, and even accumulate over time. When this happens, the aerosols then follow air flows over distances up to almost 2m.
The researchers also point out that the measurement of WHO’s physical distancing recommendation does not take into account recent studies that have detected submicron aerosols, and that they’re based on studies of respiratory droplets from the 1930s. At that time, technology used to detect submicron aerosols was not yet available.
What current research on aerosol transmission shows
Some of the latest studies on the topic have indicated that intense coughing and sneezing can lead to much larger droplets travelling more than 6m, and may also have the ability to create thousands of aerosols that can travel further than this distance.
According to a study, as reported by Health24 last month, a team of four researchers found that breathing and talking may contribute to the spread of the virus via aerosol transmission.
They offered recommendations to address aerosol transport of the virus, such as collecting more data exploring the concentration and duration of survival of the virus in its aerosol form.
Another study also found that in areas that have low ventilation and air exchange, as well as ineffective isolation measures, the virus’s RNA in aerosols may have high detection levels.
Their study was focused on two Wuhan-based government hospitals. Earlier research published in Environmental International also found that the virus can live in the air, especially in crowded indoor areas for extended periods of time.
However, despite the growing body of research on the methods of transmission of SARS-CoV-2, the authors stress that it’s still difficult to define what exactly the ideal measurement is for physical distancing.
Considering this, they emphasise the need for properly-fitted masks, as this can act as a physical barrier to the exhaled breath of asymptomatic individuals, and potentially reduce the rate of infections in countries worldwide.
They emphasise the importance of wearing these masks in high-risk areas with potentially high concentrations of the virus, including healthcare settings, restaurants, and airports, among others.
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