Written By: Satata Karmakar | Updated : February 18, 2022 1:57 PM IST
In 2019, the world saw the emergence of a deadly virus infection caused by the SARS-CoV-2. Named COVID-19, this virus led to a pandemic that the world is still fighting. Over the years, many studies have shown the characteristics of this virus and how it affects the human body. Being an airborne disease, the COVID-19 virus can easily transmit or travel from one person to another in a span of seconds, which is why this infection has been able to spread its tentacles in almost every corner of the world time in no time.
Airborne diseases are mainly those health complications that spread easily or in layman's words can transmit easily through the air. It is so deadly that airborne diseases linger in the air we breathe (especially in the dust particles and respiratory droplets). This, when gets inhaled by another person who is not even infected yet, can also catch the virus and thus get infected. COVID-19 is also an airborne disease, but, how long and how far can the coronavirus travel in the air? Let's hear it from the experts.
According to a recent study, small coronavirus respiratory particles may remain moist and airborne for a longer time and travel to a greater distance than previously thought. Yes, you heard that right. Published in the journal International Communications in Heat and Mass Transfer, a research paper has taken a long look at the mucus that coats the respiratory droplets that people spew from their lungs.
What did they find? The researchers said that the mucus allows many viruses to travel further than they otherwise would, enabling them to journey from one person to another. The conventional wisdom has been that very small, aerosolised droplets of just a few microns, like those produced in the lungs, dry out in the air almost instantly, becoming harmless. However, the recent study has something else to say. The PNNL team found that the mucus shell that surrounds respiratory droplets likely reduces the evaporation rate, increasing the time that viral particles within the droplets are kept moist.
Since enveloped viruses like SARS-CoV-2 have a fatty coating that must be kept moist for the virus to be infectious, the slower evaporation allows viral particles to be infectious longer. The research team has estimated that the droplets encased in mucus can remain moist for up to 30 minutes and travel up to about 200 feet. Talking about the study, the author said, "There are reports of people becoming infected with a coronavirus downwind of an infected person or in a room several minutes after an infected person has exited that room." He further added, "The idea that enveloped virions may remain well hydrated and thus fully infective at substantial distances is consistent with real-world observations. Perhaps infectious respiratory droplets persist longer than we have realised."
They also noted that while there are many factors proposed as variables that can be considered responsible for how COVID spreads, mucus remains largely overlooked. The authors of the study said that the focus on mucus helps address another question: how the virus moves in a multi-room office building.
In a study which was published in the journal Indoor Air, chemist Carolyn Burns created artificial, respiratory-like droplets to study how the particles moved from room to room. The research team used an airbrush to disperse droplets in one room of a multi-room laboratory building. According to the study results, the droplets and airbrushes simulated a person's coughing fit, releasing particles for about one minute in a source room. The researchers found that both low and high levels of filtering were effective at reducing levels of respiratory droplets in all rooms.
The authors said that the filtration quickly cut down the levels of droplets in the adjoining rooms -- within about three hours, to one-third the level or less without filtration. The team also found that increasing ventilation rapidly reduced particle levels in the source room. However, particle levels in the other connected rooms jumped immediately; levels spiked 20 to 45 minutes later with vigorous air changes increasing the spike.
They said that after the initial spike, levels of droplets in all the rooms gradually dropped after three hours with filtration and after five hours without it. The researchers also concluded that while increased air exchange for crowded spaces may be beneficial in certain situations, like large conferences or school assemblies, in normal work and school conditions, it may actually increase transmission rates throughout all rooms of a building. "If you're in a downstream room and you're not the source of the virus, you probably are not better off with more ventilation," one of the authors quoted as saying.
(With inputs from Agencies)
