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CDC Removes ‘Airborne’ COVID-19 Content

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In September 2020, the CDC added and then removed "airborne transmission" as a way in which COVID-19 is likely to spread.

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On September 21 2020, several prominent tweets suggested that the Centers for Disease Control and Prevention added, then removed guidance indicating that SARS-CoV-2 (the virus which causes COVID-19) was airborne — meaning it could potentially be spread through aerosolized droplets in confined spaces:

One tweet highlighted the changes:

Those tweets often followed tweets referencing and sharing the removed content from the CDC’s website:

Initial News About the CDC’s ‘Airborne Spread’ Changes

In the above tweet, published at 7:39 AM on September 21 2020, epidemiologist Eric Feigl-Ding shared a CNN link to a September 20 2020 article (“Updated CDC guidance acknowledges coronavirus can spread through the air”), which began:

The US Centers for Disease Control and Prevention updated guidance on its website to say coronavirus can commonly spread “through respiratory droplets or small particles, such as those in aerosols,” which are produced even when a person breathes.

“Airborne viruses, including COVID-19, are among the most contagious and easily spread,” the site now says.

Previously, the CDC page said that Covid-19 was thought to spread mainly between people in close contact — about 6 feet — and “through respiratory droplets produced when an infected person coughs, sneezes or talks.”

The page, updated [September 18 2020], still says Covid-19 most commonly spreads between people who are in close contact with one another, and now says the virus is known to spread “through respiratory droplets or small particles, such as those in aerosols, produced when an infected person coughs, sneezes, sings, talks or breathes.”

A separate September 21 2020 article also published on CNN.com (“As doctors worry about ‘a very apocalyptic fall,’ the CDC retracts info on how Covid-19 spreads”) addressed the removal of guidance about airborne transmission of COVID-19 from the CDC’s website:

Dr. Jeanne Marrazzo, director of the division of infectious diseases at the University of Alabama at Birmingham, said she agrees this fall “could be apocalyptic” after recent spikes.

[…]

[Marrazzo] cited a recent [September 18 2020] update from the CDC that said you can get Covid-19 just by inhaling tiny particles from an infected person’s breath that linger or travel in the air.

“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,” the CDC’s website said in an update [added September 18 2020]. “In general, indoor environments without good ventilation increase this risk.”

Many doctors have known that for months — hence their pleas for the public to wear masks.

“The updated guidance would have been fine if it came out last May [2020],” Hotez said. “We knew all of these things months ago.”

But by Monday afternoon [September 21 2020], the CDC’s update was removed.

“The fact that they retracted this, even though this is common scientific knowledge at this point, one has to wonder what’s behind it,” said Dr. Leana Wen, a CNN medical analyst and an emergency physician at George Washington University.

As for the retraction, a copy of a page titled “How COVID-19 Spreads” was updated September 18 2020, and archived just before 10 AM on September 21 2020. The archived version of the page read:

COVID-19 is thought to spread mainly through close contact from person to person, including between people who are physically near each other (within about 6 feet). People who are infected but do not show symptoms can spread the virus to others. We are still learning about how the virus spreads and the severity of illness it causes.

COVID-19 most commonly spreads

  • Between people who are in close contact with one another (within about 6 feet).
  • Through respiratory droplets or small particles, such as those in aerosols, produced when an infected person coughs, sneezes, sings, talks, or breathes.
    • These particles can be inhaled into the nose, mouth, airways, and lungs and cause infection. This is thought to be the main way the virus spreads.
    • Droplets can also land on surfaces and objects and be transferred by touch. A person may get COVID-19 by touching the surface or object that has the virus on it and then touching their own mouth, nose, or eyes. Spread from touching surfaces is not thought to be the main way the virus spreads.
  • It is possible that COVID-19 may spread through the droplets and airborne particles that are formed when a person who has COVID-19 coughs, sneezes, sings, talks, or breathes. 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). In general, indoor environments without good ventilation increase this risk.

As of 5:49 PM on September 21 2020, the same page at the same link did not include the content about airborne transmission:

COVID-19 is thought to spread mainly through close contact from person-to-person. Some people without symptoms may be able to spread the virus. We are still learning about how the virus spreads and the severity of illness it causes.

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

A note at the top of the edited page addressed the changes:

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.

CDC Officials Explain the Revision and Re-Revision

According to the second CNN article, two people with knowledge of the changes (one named, one not) spoke to the network:

The removal was not the result of political pressure, according to a federal official familiar with the situation.

“This was totally the CDC’s doing,” the official said. “It was posted by mistake. It wasn’t ready to be posted.”

The official said the guideline change was published without first being thoroughly reviewed by CDC experts.

“Somebody hit the button and shouldn’t have,” the official said.

The official added that the guidance is “getting revised,” but didn’t say when the revision would be posted to the CDC’s website … When asked why the CDC retracted its update on aerosolized spread, a spokesman for the agency said it was posted in error.

“A draft version of proposed changes to these recommendations was posted in error to the agency’s official website,” CDC spokesman Jason McDonald said in an email to CNN.

“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.”

A CNBC article published just after noon on September 21 2020 reported that the World Health Organization had contacted the Centers for Disease Control and Prevention about the changes:

The WHO had not seen any “new evidence” on airborne particles and was checking with the CDC to “better understand” the exact nature of the change, Dr. Mike Ryan, executive director of the WHO’s health emergencies program, said during a news conference at the agency’s Geneva headquarters.

The WHO has said Covid-19 primarily spreads through respiratory droplets that pass when an infected person coughs, sneezes or breathes. Studies have shown that the coronavirus could spread through aerosols in the air, and the WHO has said it is monitoring “emerging evidence” of possible airborne transmission.

The international agency’s position “on this remains the same,” Ryan said, “and we’ve always said going back over months and months about the potential for different kinds of roots of transmission and particularly driven by the context, the proximity, the intensity, the duration and the potential for different forms of transmission.”

In the same article, CNBC referenced research supporting the airborne spread of coronavirus:

Studies have suggested the virus can spread through the air. A study published by researchers at the National Institutes of Health earlier [in 2020] found that particles of the coronavirus released by talking can remain in the air for eight to 14 minutes.

A study published in the New England Journal of Medicine found that Covid-19 was detectable in aerosols for up to three hours.

In July [2020], the WHO said there is still no “definitive” evidence that indicates the virus is spreading widely by air, although it added that the possibility of airborne transmission in public settings “cannot be ruled out.”

A September 21 2020 Washington Post article quoted CDC deputy director for infectious disease Jay Butler, who said the CDC could not explain how the “airborne” guidance was initially published:

But Jay Butler, the CDC’s deputy director for infectious disease, said the Friday update was posted in error. “Unfortunately an early draft of a revision went up without any technical review,” he said.

The edited Web page has removed all references to airborne spread, except for a disclaimer that recommendations based on this mode of transmission are under review. “We are returning to the earlier version and revisiting that process,” Butler said. “It was a failure of process at CDC.”

Summary

On September 18 2020, a CDC page called “How COVID-19 Spreads” was updated to include prominent initial language about airborne coronavirus transmission. The changes attracted widespread attention on September 20 2020, and the updates were taken out of the CDC page the next day. Officials later said that “an early draft of a revision went up without any technical review,” because of “a failure of process at [the] CDC,” and that edits to the page were pending.