We know you are getting tired of reading about the coronavirus. We are exhausted writing about it. But as long as people continue to argue about face masks and routes of transmission, we feel it is important to share the science. How good are masks at preventing the spread of COVID-19? A new study in AIP Advances (online, April 6, 2021) reports that there is huge variability. If N95 masks don’t fit well, even they may not protect people. It is entirely possible to contract COVID-19 simply by breathing contaminated air. Ventilation systems play a key role in the spread of aerosolized SARS-CoV-2. What is the ventilation like in your home, apartment, bank, grocery store or office?
Will Face Masks Protect You?
The last time we checked, roughly 20 percent of the population of the US has been fully vaccinated (CDC, April 8, 2021). That’s impressive! But it also means that 4 out of every 5 Americans have not been fully vaccinated.
No doubt you are aware that many states have opened up and are now allowing people to resume normal activities. That means shopping, dining and doing the normal errands of everyday life. Many people are wearing masks so they won’t contract COVID-19. But do they fit well enough to work?
Not all masks are created equal. Researchers in India have just reported on some intriguing experiments (AIP Advances (online, April 6, 2021). By the way, India is experiencing a terrible COVID outbreak right now. You can read about the dire situation there and find out what is happening across the US in this article.
Breathing Spreads Aerosol Particles:
There was a lot of concern about coughing and sneezing early in the pandemic. The real problem may be as simple as breathing.
The Indian scientists note that:
“The infected person’s exhaled breath may carry virus-bearing aerosol droplets, which may remain suspended in the air.”
While surgical masks can filter large droplets, they don’t do a great job against smaller aerosol particles. The researchers created breathing simulators to determine how well various masks work at filtering out aerosols.
What They Did:
They used a mannequin with a mechanical breathing simulator and a fog generator that produced particles from 1 to 10 micrometers in diameter. When the mannequin had no face covering, droplets from simulated breath zoomed up to 4 feet in just 5 seconds.
Two-layer cotton masks were not very effective. A surgical mask allowed significant leakage. However, a commercial 5-layer mask provided good protection. The commercial N95 mask was not quite as good, as there were leaks at the top of the mask where it didn’t conform closely to the nose.
You can see their research and the photographs of aerosol particles at this link.
Fitting a Face Mask:
You have no doubt seen politicians and other “important” people making speeches while their face mask slips down below their nose. It WON’T WORK unless it covers the nose and fits snugly. We often see gaps around the cheeks and under the chin. Just look at the photo at the top of this page for a perfect example of the wrong way to wear a face mask. Many face masks just do not fit very well.
We agree with the scientists from India when they conclude:
“The present study highlights that there is a need for innovation in face mask design, which can prevent the leakage of the droplets with adequate human comfort.”
The bottom line is that indoor spaces need excellent fresh air ventilation to maintain good air quality, even if people are masked. People who do not want to contract COVID-19 will need to have high-quality, well-fitting face masks and pay attention to the quality of the air around them.
An Accidental Experiment in a Nursing Home:
Dutch researchers report the importance of aerosol transmission when patients contract COVID-19 (Clinical Infectious Disease, Aug. 28, 2020). They describe an outbreak in one unit of a nursing home.
The authors introduce their study this way:
“Recently, we were involved in an outbreak in a Dutch nursing home that was likely to be the result of aerosol transmission in a setting of inadequate ventilation.”
The ward in question had been renovated. It had an unusual, energy-efficient ventilating system that brought in fresh outside air only when carbon dioxide levels started building up:
“If the CO2 concentration did not exceed 1000 ppm, the ventilation cabinets recirculated indoor air back into the ward without filtration.”
Because many of the elderly patients in this ward were inactive, carbon dioxide levels didn’t build up quickly. As a result, the stale, air-conditioned air was recirculated within the shared living space. This ventilation system may have been energy efficient and cost saving, but it had devastating coronavirus consequences.
Aerosol Transmission of COVID-19:
The investigators report that 81% of the residents in this ward and 50% of the healthcare staff came down with COVID-19.
The health care workers (HCWs) did wear face masks when interacting with patients:
“To prevent and control COVID-19 infections all HCWs in this nursing home had been assigned to specific wards and did wear surgical masks during patient contacts since April 26, 2020. HCWs did not wear masks during not patient related activities and breaks.”
The air in this ward circulated throughout the entire building. COVID-19 was detected on the air filters within the ventilation system. It is likely that the health care workers were able to contract COVID-19 when they were not directly interacting with patients and had taken off their masks.
Good Ventilation Worked:
In the six other wards of the nursing home, where outside air was a key part of the ventilation system, none of the 106 health care workers or 95 residents became sick.
The authors advise that:
“…prevention of COVID-19 transmission should take into account the possibility of aerosol transmission in healthcare facilities and other buildings where ventilation systems recirculate unfiltered inside air.”
Buddhists Contract COVID-19 Inside a Bus:
Here is another example of how people can contract COVID-19 just by breathing air containing aerosolized particles of SARS-CoV-2 (JAMA Internal Medicine, Sept. 1, 2020). The authors pose this question:
“Is airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) a potential mean[s] of spreading coronavirus disease 2019 (COVID-19)?”
The investigators point out that:
“…closed environments may facilitate secondary transmission of SARS-CoV-2. An experimental study demonstrated that SARS-CoV-2 can remain viable in aerosols for 3 hours or longer, and experimental evidence of transmission of SARS-CoV-2 between ferrets via the air was also established. Therefore, evidence supporting the potential for an airborne transmission route of SARS-CoV-2 is emerging. However, epidemiologic evidence from actual community transmission in human cohorts is lacking.”
This research attempts to supply much-needed data. A Buddhist worship event took place in Ningbo, China, on January 19. Although Ningbo is 700 km east of Wuhan, on that date there had been no COVID-19 cases reported in Ningbo city, and the 126 people traveling on two buses did not wear masks during their 50-minute ride to the event.
Catching COVID-19 from a Bus Ride:
Unbeknownst to them all, one of the passengers was already infected. Later, 23 of the 65 other riders who shared that bus developed symptoms and were diagnosed with COVID-19. None of those on the other bus became infected, although people from each bus were not separated during the outdoor worship event or luncheon.
The air system in the bus recirculated air. In other words, the ventilation system on the bus was not that different from the ventilation system in the nursing home in the Netherlands that recirculated stale air. The passengers and the driver sitting near the door and a window that opened did not become infected.
The trip took 50 minutes each way. So breathing air containing SARS-CoV-2 for about 100 minutes was sufficient for about one-third of the passengers to contract COVID-19. Imagine sitting in a dining room, a church or a classroom for about an hour and a half. If someone were sick, the viral particles could easily circulate though the air if the ventilation system was not very good.
The scientists conclude:
“These data suggest that forced, circulating air might play an important role in airborne spread of the virus, and gatherings in enclosed settings with minimal air ventilation should be limited.”
Breathing Out Viral Particles:
Chinese researchers also report the results of samples they collected during the active phase of the pandemic in Beijing (Clinical Infectious Diseases, Aug. 28, 2020). They recruited a total of 76 volunteers, including 57 patients with COVID-19. There were 15 healthy subjects in the study. The scientists sampled 242 surfaces in patient rooms or other areas being used by quarantined patients. In addition, the volunteers provided exhaled breath samples.
Analysis of the samples showed SARS-CoV-2 virus in 27% of the breath samples, but only 5% of surface samples. For example, only 2 of 22 patient mobile phones yielded virus.
Some of the exhaled breath samples contained millions of virus particles per minute, especially in early stages of infection. With so few surfaces testing positive, it seems likely that virus from infected patients’ breath is how people contract COVID-19.
The Bottom Line on How People Contract COVID-19:
The most likely way people contract COVID-19 is by breathing aerosolized particles containing the virus. It is highly contagious, as the stories above reveal. Whether it’s at a nursing home, a bus or a wedding reception, ventilation systems can spread the virus far and wide. And it seems as if viral particles can float in the air for hours.
We know that a lot of visitors to this website believe that face masks are worthless. We have been berated for suggesting that facial coverings might be beneficial at this link. The quality of the face mask and how well it fits are likely the most important variables.
For people who do not want to contract COVID-19, we suggest you listen to one of the world’s foremost authorities on the transmission of aerosol particles like SARS-CoV-2. Dr. Linsey Marr is a guest on our syndicated public radio show Saturday morning, April 10, 2021, at 7:00 am Eastern Daylight Time. You can listen to the live streaming audio at one of our stations (here is a list of stations and links). The podcast can be downloaded from this site on Monday morning. Here is a link to the show:
Show 1253: The Lessons of COVID-19 on How to Avoid Airborne Viral Transmission
Evidence shows that SARS-CoV-2, the coronavirus that causes COVID-19, moves like an aerosol. How can we avoid airborne viral transmission?
What do you think? How do people contract COVID-19? Please share your thoughts (in a respectful and non-political way) in the comment section below. If you think this article is worthwhile, please share it with friends, family and co-workers. There are icons at the top of this page that allow you to email it or put it on Facebook or Twitter.
