Public health organizations such as the WHO and CDC have recently done an about-face on aerosol spread of SARS-CoV-2. Experts who have studied transmission of the virus have long maintained that it travels in tiny aerosol particles that can drift far from an infected person and stay airborne for hours. That contradicted the droplet dogma that most transmission was through close personal contact and relatively large globs of virus. Some experts have taken to calling aerosol particles “micro droplets” that can linger in air and travel long distances.
For decades the public health message was that if you stayed at least six feet apart you could avoid infection. That turns out not to be true for viruses like SARS-CoV-2 that can float on air. Improving ventilation is key to reducing risk. Some experts suggest a simple, old-fashioned approach: open the windows. Portable air cleaners and ultraviolet lights could also help. Monitoring indoor air quality with an eye toward improving it would provide some protection not only from COVID but also from colds and the flu (Science, May 14, 2021). This idea has been surprisingly controversial over the course of the pandemic.
Losing Faith in Public Health Dogma:
On Monday, October 5, 2020, the CDC went from flip-flop-flip back to FLOP! That was the day this once-respected public health agency admitted that aerosol spread of COVID-19 is a thing:
- “Airborne transmission is infection spread through exposure to those virus-containing respiratory droplets comprised of smaller droplets and particles that can remain suspended in the air over long distances (usually greater than 6 feet) and time (typically hours). “
The Old CDC Stance:
For months, the Centers for Disease Control and Prevention (CDC) had been asserting that people primarily catch the coronavirus by breathing in large infected “droplets.” The feds insist that this only occurs when people stand within six feet of someone who has COVID-19.
In this scenario the droplets fly through the air when someone coughs, sneezes or talks. They land on someone close by and are inhaled through the nose or mouth.
The CDC experts maintain that because droplets are big, they are pulled down quickly to the floor by gravity. If you stand seven feet away from an infected person, the theory goes that the droplets can’t reach that far and you will be safe.
The Big Flop on Aerosol Spread!
That was the old thinking until September 18, 2020. On that day the CDC changed its old “guidance.” The new thinking was that aerosol spread of the coronavirus could occur via tiny particles as well as through droplets. The agency stated that the SARS-CoV-2 virus could be transmitted through:
“…small particles, such as those in aerosols, produced when an infected person coughs, sneezes, sings, talks or breathes.”
The CDC went on to note that aerosol spread of the coronavirus can happen when an uninfected person inhales particles through the nose and mouth.
The feds went so far as to state that this was the primary way people catch COVID-19:
“There is growing evidence that droplets and airborne particles can remain suspended in the air and be breathed in by others, and travel distances beyond 6 feet (for example, during choir practice, in restaurants or in fitness classes.”
The CDC suggested that any indoor environment without good air ventilation poses a risk for aerosol spread. It also went on to encourage people to “stay at least 6 feet away from others, whenever possible.” That was a bit different from staying “about” 6 feet away. Such a small difference hardly seems worth noting, but it got someone’s attention.
The U-Turn Flip on Aerosol Spread!
On Monday, September 21, 2020, the CDC did a big boomerang. We went from the flop back to the flip.
The old guidance was back. The idea of aerosol spread seemed to have dissipated.
Here was the CDC’s web page reversal explanation (Sept. 21, 2020):
“A draft version of proposed changes to these recommendations was posted in error to the agency’s official website. CDC is currently updating its recommendations regarding airborne transmission of SARS-CoV-2 (the virus that causes COVID-19). Once this process has been completed, the update language will be posted.”
The CDC message about aerosol spread went back to this:
“Person-to-person spread”
“The virus is thought to spread mainly from person-to-person.
• Between people who are in close contact with one another (within about 6 feet).
• Through respiratory droplets produced when an infected person coughs, sneezes, or talks.
• These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs.
• COVID-19 may be spread by people who are not showing symptoms.”
This is the fastest no-yes-no about-face we have seen from the CDC. We can tell you that a CDC “guidance” doesn’t get posted without thoughtful review. That is especially true when it involves something as controversial as a change in thinking about the aerosol spread of COVID-19.
Someone clearly did not like the idea that that small viral particles might float in the air beyond six feet. If the virus can remain airborne beyond six feet for minutes or longer, it poses a significant threat. Now the CDC has reversed course yet again!
The Flip-Flop-Flip Has now Flopped Again!
On October 5, 2020, the CDC issued a “new” message about airborne transmission of the coronavirus. It seems to us that the image of the CDC has been tarnished with the flip-flop-flip-flop. In its attempt to explain this, the agency has trotted out some fairly complex word-smithing:
“The term ‘airborne transmission’ has a specialized meaning in public health practice
“Airborne can be used to describe any size particle (e.g., droplet, dust, pollen) capable of travel through the air. For respiratory droplets, that can include droplets that are close to the source and those that have moved farther away. However, most infectious disease and public health experts reserve the term airborne specifically for use in the context of airborne transmission to describe infections capable of being transmitted through exposure to infectious, pathogen-containing, small droplets and particles suspended in the air over long distances and that persist in the air for long times.”
The CDC still maintains that “COVID-19 most commonly spreads during close contact.” In other words, within the magic six feet. And the concept of droplet remains dominant. But the CDC’s public health experts have apparently prevailed. The new guidance admits that in some situations people can catch SARS-CoV-2 through small aerosol particles beyond six feet. But as you will read, there is a lot of derriere covering, or as we like to abbreviate: CYA.
In its own words, here is the CDC’s latest FLOP statement:
- “There is evidence that under certain conditions, people with COVID-19 seem to have infected others who were more than 6 feet away. These transmissions occurred within enclosed spaces that had inadequate ventilation. Sometimes the infected person was breathing heavily, for example while singing or exercising.
- Under these circumstances, scientists believe that the amount of infectious smaller droplets and particles produced by the people with COVID-19 became concentrated enough to spread the virus to other people. The people who were infected were in the same space during the same time or shortly after the person with COVID-19 had left.
- Available data indicate that it is much more common for the virus that causes COVID-19 to spread through close contact with a person who has COVID-19 than through airborne transmission.”
What Do the Experts Say?
Dr. Linsey Marr told the New York Times (September 21, 2020):
“‘In the scientific community, it’s become very clear that aerosols are very important,’ said Linsey Marr, an expert in airborne viruses at Virginia Tech. ‘I hope that it comes back in some form that acknowledges the importance of aerosols.’”
Dr. Marr was referring the the about face from the CDC. She believes that aerosol spread of small viral particles should be in the CDC guidance on how to avoid COVID-19.
Do You Believe in Science?
If you think science is important and you are concerned about aerosol spread, we encourage you to listen to our free People’s Pharmacy podcast. We were honored to have two of the world’s experts on aerosol spread of COVID-19 as guests on our syndicated public radio show.
Dr. Linsey Marr and Dr. Richard Corsi were kind enough to spend a lot of time with us explaining how the coronavirus moves through air. These are world-class researchers and great communicators.
Even if you listened to our radio Show 1227, you will want to listen to this extended podcast. That’s because Dr. Corsi provides much more detailed information. You can learn about air filters, UV air purifiers and ventilation systems.
What Do You Need to Know About Airborne Virus?
Ventilation is crucially important when it comes to preventing the spread of airborne virus. Learn how to protect yourself.
There are three ways to listen. Under the photograph of Dr. Marr there is a green circle with an arrow inside. Just click on the arrow to stream the audio on your computer or device. Super easy!
If you are used to downloading mp3 files, just scroll to the bottom of the page. There is a link to download the “free mp3.”
What Do You Think?
What do you make of the CDC flip, flop, flip, flop? Are you getting tired of all the chaos? You can share your thoughts in the comment section below. Please be respectful.
