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 report the science. This week there were three studies confirming that people contract COVID-19 simply by breathing in viral particles. 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? Let’s look at the research.
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 during the last week of June.
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 Wedding in Millinocket, Maine:
By now we suspect that you have heard about the wedding in the small town of Millinocket, Maine, on August 7, 2020. In the last census (2010), the population was 4,506 people. There were no cases of COVID-19 in Millinocket prior to the wedding. On that day, 65 people gathered at the Big Moose Inn to celebrate a marriage. People were not wearing masks and were not maintaining much distance between themselves. No one seemed sick.
The next day, though, one person began developing symptoms of COVID-19. As of yesterday (September 3, 2020), public health authorities report that 144 people have come down with the coronavirus and two have died.
How did so many people contract COVID-19? Of the 65 people who attended the wedding, 56 guests and their friends and family members caught SARS-CoV-2. Those people went on to spread it to 46 inmates and 19 staff members at a jail. The Maplecrest Rehabilitation & Living Center is about two hours away from Millinocket, Maine. At this time it is reported that 16 residents and employees of that facility came down with COVID-19 as a result of indirect contact with someone at the wedding.
No one knows how many more people will contract COVID-19 because of the wedding celebration. The public health authorities are looking into an outbreak in and around Sanford, Maine. It is 233 miles from Millinocket. The minister who performed the wedding flew his plane to Millinocket from Sanford. It is not clear whether the case associated with his church is related to the wedding in Millinocket.
The Bottom Line on How People Contract COVID-19:
We suspect that some individuals contract COVID-19 from fomites. Those are objects that may have been contaminated with the virus such as doorknobs, gas pumps or elevator buttons. But we suspect that such cases are relatively rare.
The most likely way people contract COVID-19 is by breathing aerosolized particles of 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.
Why Are People So Confused About Face Masks?
Face masks remain polarizing. There have been fights and deaths over facial coverings. Why are Americans still so confused about face masks?
For people who do not want to contract COVID-19, we have few other ways to avoid breathing aerosolized viral particles when we are in places that might not have great fresh air ventilation.
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