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Airborne Coronavirus Particles May Go Further Than Thought: Lab Study


Airborne Coronavirus Particles May Go Further Than Thought: Lab Study

The team estimates that the droplets encased in mucus can stay moist for up to 30 minutes

Washington:

A study conducted in a laboratory found that small coronavirus respiratory particles can remain moist in the air for longer periods of time and travel longer distances than previously thought.

The study, published in the journal International Communications in Heat and Mass Transfer, took a long look at the mucus that coats respiratory droplets that people spew from their lungs.

Researchers from the US Department of Energy’s Pacific Northwest National Laboratory (PNNL) note that mucus allows many viruses to travel farther than they otherwise would, allowing them to migrate transfer from one person to another.

Conventional wisdom holds that very small aerosol droplets, just a few micrometers, like those produced in the lungs, dry up in the air almost instantly, becoming harmless.

However, the PNNL team found that the mucous coating surrounding respiratory droplets can reduce the rate of evaporation, increasing the retention time of viral particles inside the droplets.

Since enveloped viruses such as SARS-CoV-2 have a fatty coating that must be kept moist for the virus to infect, slower evaporation allows the viral particles to infect longer.

The team estimates that droplets encased in mucus can stay moist for up to 30 minutes and travel up to about 200 feet.

“There are reports of people getting the coronavirus downwind of an infected person or in a room minutes after the infected person has left that room,” said Leonard Pease, the study’s corresponding author. ,” Leonard Pease, the study’s corresponding author.

Pease added: “The idea that enveloped virions can remain well hydrated and thus be fully infectious at considerable distances is consistent with real-world observations.

The researchers note that although many factors have been suggested as variables in how COVID is spread, mucus is largely ignored.

Focusing on mucus, they say, helps address another question: how does the virus travel in a multi-room office building.

In another study published in the journal Indoor Air, chemist Carolyn Burns created artificial respiratory-like droplets to study how particles move from room to room.

The team led by Alex Vlachokostas and Burns used an airbrush to disperse droplets in one room of a multi-room laboratory building.

The drops and airbrush simulate a person’s cough, releasing particles for about a minute in the source room.

The researchers found that both low and high filtration levels were effective in reducing levels of respiratory droplets in all rooms.

They say the filtration quickly cuts down on droplet levels in adjacent rooms – within about three hours, to a third of the level or less without filtration.

The team also found that increased ventilation rapidly reduced particle levels in the source room.

However, particle levels in other connected rooms increased immediately; spike 20 to 45 minutes later with a drastic change in air increasing the spike.

After the initial spike, droplet levels in all rooms gradually decreased after three hours with filtration and after five hours without it, the researchers said.

They conclude that while increasing air exchange for crowded spaces can be beneficial in certain situations, like large conferences or schools, under normal school and work conditions, it does can increase the transmission rate through all rooms of the building.

Pease added: “If you’re in a downstairs room and you’re not the source of the virus, you probably shouldn’t be ventilating more.

(Except for the title, this story has not been edited by NDTV staff and is published from an aggregated feed.)



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