Here we are, more than 2.5 years into the worst pandemic since 1918 and people seem oblivious to how they can catch the coronavirus. Many are still arguing. The debate is over airborne transmission of COVID-19! A systematic review published in the BMJ (formerly the British Medical Journal) on June 29, 2022 should settle the issue once and for all.
Why should you care? Because a lot of people are currently catching COVID! That includes people who have been vaccinated and boosted as well as those who caught COVID once or twice before. Even those who have been careful and managed to avoid the SARS-CoV-2 virus are now becoming ill. Add Dr. Anthony Fauci to the list of new COVID victims. The latest research can help you avoid getting sick, transmitting the infection and/or developing long COVID.
Why Understanding Aerosol Transmission of COVID-19 Matters!
It is hard to avoid catching COVID unless you truly understand how SARS-CoV-2 moves through the air. That includes traveling on buses, trains or airplanes. It also concerns supermarkets, banks, pharmacies, office buildings, schools, restrooms and restaurants.
The bottom line, based on the latest BMJ (June 29, 2022) review, makes it clear how people catch COVID. It is:
Airborne Transmission of COVID-19!
Here is what the authors did:
“As evidence on the biological plausibility of long distance airborne transmission is available from environmental and experimental studies, we focused on epidemiological observational studies to assess where and when human-to-human transmission are likely to occur. In this rapid review we systematically identified and examined such studies to evaluate the potential for long distance airborne transmission of SARS-CoV-2 in indoor community settings and to assess the impact of potential modifying factors.”
The 18 studies covered COVID outbreaks in various community settings between 2020 and 2022. These included singing events, church services, a fitness facility, restaurants, buses, a courtroom, an office, a food processing factory, a department store, apartment buildings and quarantine hotels. Individuals identified as the source of the infection were often asymptomatic or pre-symptomatic.
Here is what the authors discovered:
“Evidence from the outbreak investigations discussed in this review suggests that airborne transmission of SARS-CoV-2 from an infectious individual to others located >2 m away [that’s more than 6 feet apart] can occur in different indoor non-healthcare settings…This finding is consistent with wider evidence that people with asymptomatic or presymptomatic SARS-CoV-2 infection can contribute to the community spread of covid-19, including from long distance airborne transmission.”
In other words, transmission of COVID-19 occurs at distances greater than 6 feet. If you are walking in a store, office building, bank or even an apartment, you could easily be exposed to the latest highly contagious variant of the coronavirus. Ditto for sitting in a restaurant, bar, movie theater or concert. The epidemiologists identified several factors associated with transmission. Chief among them was inadequate air replacement or inappropriate air flow direction.
What the authors recommend to avoid transmission of COVID-19:
“The results of this review therefore confirm the importance of the role of ventilation to mitigate the risk of long distance aerosol transmission.”
“The results from this rapid systematic review highlight the need to ensure measures to mitigate SARSCoV-2 long distance transmission in indoor settings, especially in poorly ventilated spaces. Identification of poorly ventilated public spaces should be undertaken and improvements made.”
Transmission of COVID-19 Is Invisible!
As I watch people walking unmasked through airports, big box stores and offices I realize that they no longer care if they catch COVID. That’s because they cannot see the danger. If red smoke were wafting through the air it would be a very different matter. No one would want to breathe those very visible aerosol particles. But airborne particles containing SARSCoV-2 are invisible!
Aerosols vs. Droplets?
Here is how three very smart Harvard physicians describe the difference between droplets and aerosols (JAMA, August 4, 2020).
“Droplets are classically described as larger entities (>5 μm) that rapidly drop to the ground by force of gravity, typically within 3 to 6 feet of the source person. Aerosols are smaller particles (≤5 μm) that rapidly evaporate in the air, leaving behind droplet nuclei that are small enough and light enough to remain suspended in the air for hours (analogous to pollen).”
If you would like to better understand the difference between greater (>) or less than (≤) 5 microns, here is an article we wrote to give you some sense of proportions. This link compares the thickness of a sheet of toilet paper to an E. coli bacterium to the flu virus to the coronavirus:
Can You Catch COVID-19 By Breathing Aerosolized Viral Particles?
Are you worried about catching the coronavirus? How far away from others do you have to be to stay safe? Is it possible to catch COVID-19 just by breathing?
Size Matters when It Comes to Transmission of COVID-19:
Here is why the size of aerosol particles carrying SARS-CoV-2 is so important. If droplets are the primary mode of transmission of COVID-19, a face mask will be protective, especially if people stay at least six feet away from each other.
If smaller aerosols are the transport vehicles for SARS-CoV-2, we’ve got problems according to the Harvard scientists.
They note that if the coronavirus is transported by:
“…aerosols that can remain suspended in the air for prolonged periods, medical masks would be inadequate (because aerosols can both penetrate and circumnavigate masks), face shields would provide only partial protection (because there are open gaps between the shield and the wearer’s face), and 6 feet of separation would not provide protection from aerosols that remain suspended in the air or are carried by currents.”
The authors point out that speaking can send aerosol particles distances of up to 27 feet and that SARS-CoV-2 can “…remain suspended in the air and viable for hours…”
In other words, the asymptomatic but contagious person who is sitting at a nearby table in a restaurant could be sending coronavirus particles in your direction for over an hour. Ditto for the person sitting behind you in a movie theatre or on an airplane.
Travel and Aerosol Transmission of COVID-19:
How risky is travel in the age of COVID-19? This question was addressed by Chinese and British scientists (Clinical Infectious Diseases, July 29, 2020) They collected data on Chinese passengers on high-speed trains between December, 2019 and March, 2020.
Passengers sitting next to an infected individual had a 3.5% chance of catching the coronavirus. For every additional hour of travel next to an infected person, the risk rose by 1.3%. The risk of transmission is related to both time and distance spent near a person with COVID.
Moving around the train to visit the restroom or obtain food or beverages also increases the chance for spread.
“When a passenger leaves a window or middle seat, the other passengers in the row need to let them pass, potentially increasing close face-to-face.”
So, what are the conclusions from this study of train passengers?
“Therefore, social distancing is an important method of reducing the risk of disease transmission on public transportation. The allocation of passenger seats on a train should be carefully considered to reduce the risk of transmission. Given the attack rates estimated for passengers on seats within the same row as the index patient, it follows that within 1 hour spent together, the safe social distance is more than 1 meter. After 2 hours of contact, a distance of less than 2.5 m can be insufficient to prevent transmission.”
We suspect that this would apply to buses, subways and airplanes as well as trains.
What Will It Take To Convince People There Is Aerosol Transmission of COVID-19?
An editorial in the BMJ (June 20, 2022) accompanies the most recent research on transmission of COVID-19.
The author noted:
“Just as the world woke up to a pandemic, a small group of determined scientists (including this author) appealed for consideration of airborne spread. Their advice was summarily dismissed. And so the group—in common with the pioneers of tuberculosis transmission—’provided an ingredient that scientists seldom mention: a mission to convince unbelievers.'”
This microbiologist, Dr. Stephanie Dancer, points out that the new research:
“…validates the premise that tiny respiratory particles containing SARS-CoV-2 freely transmit throughout inadequately ventilated environments.”
How Can People Avoid Transmission of COVID-19?
Dr. Dancer states that better indoor air quality is crucial. She concludes:
“Now, indeed, is the time for an indoor air revolution.”
Optimizing indoor ventilation may be a lot harder than most people think. There was a time when people could open windows and let fresh air in. That is uncommon these days. For decades, builders have tried to make houses, offices and apartments as “tight” as possible to improve heating and cooling efficiency. There is even something called “sick building syndrome.” It is often attributed to poor air quality.
Restrooms, restaurants, office buildings, factories, pharmacies and lots of other public spaces have highly variable air quality. Some locations provide lots of fresh air, while others offer very little. Some have excellent air filtration systems but others do not. There is almost no way to know.
So…Do Masks Make a Difference Against Transmission of COVID-19?
We are not about to fight what has become such a politicized issue. What we will do is cite a recent review article published in Public Health Practice (Oxford), online, June 13, 2022). These investigators looked at 461 reviews and 208 primary studies. They settled on 16 systematic reviews including 11 observational studies that met their quality criteria. They were especially interested in how well personal protective equipment (PPE) and face masks protect healthcare workers (HCWs) against COVID-19.
And the envelope please:
“Overall, the review results show that wearing face masks can significantly protect HCWs from infection.”
And the conclusions please:
“This evidence supports PPE use by HCW, and especially N95 masks, to reduce the risk of a COVID-19 infection.”
What to Do Going Forward to Stop Transmission of COVID-19?
We know that most Americans are not going back to wearing face masks. That is reality. Even if there are new variants that are highly contagious and escape vaccinations or prior immunity, most people are not putting on face masks again. So what is left to avoid catching the coronavirus?
As far as we can tell, there is only one strategy that might work. That is an “indoor air revolution.” We need better air quality, period. Full Stop!
What Do You Think?
We would love to read your perspective in the comment section below. Do you believe it would be beneficial if our heating and air-conditioning experts improved air quality? Should our schools install UV germicidal devices in the duct work along with improved air filters? What about in offices, banks, pharmacies, stores, doctors’ offices or apartment buildings?
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