Covid-19 droplets can remain on a surface in case of high humidity: Study

Prashasti Awasthi Mumbai | Updated on August 20, 2020

According to researchers, the droplets exhaled by an infectious individual contain virus particles as well as other substances, such as water, lipids, proteins, and salt

According to a new study published in the journal Physics of Fluids, coronavirus droplets can remain on the surface in case of high humidity. This directly leads to the extension of the lifetime of the airborne virus.

The researchers stated in their study that the Covid-19 is thought to be transmitted by natural respiratory activities, such as breathing, talking and coughing, but little is known about how the virus is transported through the air.

The study analysed how airflow and fluid flow spread the virus-infected droplets.

The model developed by researchers at the University of Missouri in the US examined the impact of air on the trajectory of exhaled droplets.

One of the authors Binbin Wang stated in his study: “If the virus load associated with the droplets is proportional to the volume, almost 70 per cent of the virus would be deposited on the ground during a cough,”

“Maintaining physical distancing would significantly remediate the spread of this disease through reducing the deposition of droplets onto people and by reducing the probability of inhalation of aerosols near the infectious source,” Wang added.

According to the researchers, droplets exhaled in normal human breath come in a range of sizes, from about one-tenth of a micron to 1,000 microns.

For comparison, a human hair has a diameter of about 70 microns, while a typical coronavirus particle is less than one-tenth of a micron, they said.

The team noted that the most common exhaled droplets are about 50 to 100 microns in diameter.

The droplets exhaled by an infectious individual contain virus particles as well as other substances, such as water, lipids, proteins, and salt, the researchers mentioned.

Their study also analyzed the interaction of the droplets with the surrounding environment, mainly through evaporation.

The researchers used an improved description of air turbulence to account for natural fluctuations in air currents around the ejected droplet.

The researchers found that humidity impact the trajectory of exhaled droplets since dry air can accelerate natural evaporation.

In the air with 100 per cent relative humidity, the simulations show larger droplets that are 100 microns in diameter fall to the ground approximately six feet from the source of exhalation, they said.

Smaller droplets of 50 microns in diameter can travel further, as much as five meters, or about 16 feet, in very humid air, as per the authors of the study.

They added that less humid air could slow the spread.

At a relative humidity of 50 per cent, none of the 50-micron droplets travelled beyond 3.5 meters, they said.

Published on August 20, 2020

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