Updated CDC guidance acknowledges coronavirus can spread through the air

The US Centers for Disease Control and Prevention updated guidance on its website to say coronavirus can commonly spread "through respiratory droplets or sma...

Posted: Sep 21, 2020 7:37 AM
Updated: Sep 21, 2020 7:38 AM

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 Friday, 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."

These particles can cause infection when "inhaled into the nose, mouth, airways, and lungs," it says. "This is thought to be the main way the virus spreads."

"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 page now says. "In general, indoor environments without good ventilation increase this risk."

The CDC also added new measures to its information about protecting yourself and others.

Previously, CDC suggested maintaining "good social distance" of about 6 feet, washing hands, routinely cleaning and disinfecting surfaces and covering your mouth and nose with a mask when around others.

Now, it says "stay at least 6 feet away from others, whenever possible," and continues to direct people to wear a mask and routinely clean and disinfect. However, it also now says people should stay home and isolate when sick, and "use air purifiers to help reduce airborne germs in indoor spaces."

Masks, it notes, should not replace other prevention measures.

The update also changed language around asymptomatic transmission, shifting from saying "some people without symptoms may be able to spread the virus" to saying "people who are infected but do not show symptoms can spread the virus to others."

Scientists pushed for acknowledgment of airborne transmission

For months, scientists have noted the likelihood of coronavirus transmission through viral particles in the air, and pushed health agencies to acknowledge it.

In April, a prestigious scientific panel told the White House in a letter that research showed coronavirus can be spread not just by sneezes or coughs, but also just by talking, or possibly even just breathing.

"While the current [coronavirus] specific research is limited, the results of available studies are consistent with aerosolization of virus from normal breathing," according to the letter, written by Dr. Harvey Fineberg, former dean of the Harvard School of Public Health and chair of the NAS' Standing Committee on Emerging Infectious Diseases and 21st Century Health Threats.

"Currently available research supports the possibility that [coronavirus] could be spread via bioaerosols generated directly by patients' exhalation," the letter said.

And in July, 239 scientists published a letter that urged the World Health Organization and other public health organizations to be more forthcoming about the likelihood that people could catch the virus from droplets that were floating in the air.

"The current guidance from numerous international and national bodies focuses on hand washing, maintaining social distancing, and droplet precautions," scientists wrote in the letter, published in the journal Clinical Infectious Diseases.

"Most public health organizations, including the World Health Organization, do not recognize airborne transmission except for aerosol-generating procedures performed in healthcare settings. Hand washing and social distancing are appropriate, but in our view, insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people," they added.

After the letter published, WHO released a report that detailed how the coronavirus can pass from one person to another, including through the air during certain medical procedures and possibly the air in crowded indoor spaces.

On Sunday, one of the lead authors of the letter, Donald Milton, a professor of environmental health at the University of Maryland who studies how viruses are transmitted, said the CDC's new language was a "major improvement."

"I'm very encouraged to see that the CDC is paying attention and moving with the science. The evidence is accumulating," Milton wrote in an email to CNN.

He described a pre-print paper released in August -- in which scientists described culturing viable virus from air in a hospital -- as "an important addition to the reports of large outbreaks that were clearly a result of transmission by aerosols that travel more than 6 feet."

"It is time for WHO to acknowledge these advancements in the science," Milton said.

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Alabama Coronavirus Cases

Confirmed Cases: 159439

Reported Deaths: 2699
CountyConfirmedDeaths
Jefferson23443377
Mobile16934315
Tuscaloosa10414140
Montgomery10298197
Madison939496
Shelby743663
Baldwin669469
Lee655065
Calhoun462161
Marshall441150
Etowah431251
Morgan418235
Houston418034
DeKalb346129
Elmore322753
St. Clair299942
Limestone289330
Walker282392
Talladega267435
Cullman250824
Lauderdale231342
Jackson217515
Autauga207431
Franklin206131
Colbert204132
Russell19533
Blount194225
Chilton189332
Dallas187227
Coffee179511
Dale177251
Covington175529
Escambia173030
Clarke135317
Chambers135244
Pike134413
Tallapoosa133087
Marion109729
Barbour10339
Marengo102522
Butler101340
Winston93713
Geneva9167
Lawrence86132
Pickens86018
Bibb84314
Randolph82916
Hale77730
Clay74912
Washington74912
Cherokee74514
Henry7196
Lowndes71428
Bullock64917
Monroe64810
Crenshaw60930
Perry5936
Fayette58413
Cleburne5738
Wilcox57012
Conecuh56113
Macon53720
Lamar5065
Sumter47321
Choctaw39212
Greene34616
Coosa2053
Out of AL00
Unassigned00

Tennessee Coronavirus Cases

Confirmed Cases: 249866

Reported Deaths: 3163
CountyConfirmedDeaths
Shelby36685565
Davidson31975343
Knox1284891
Rutherford12017115
Hamilton11867109
Williamson718756
Sumner6184112
Wilson473159
Putnam445657
Montgomery424057
Out of TN415136
Sullivan381946
Madison381479
Bradley361923
Washington356951
Maury338938
Blount337436
Sevier336423
Robertson262842
Hamblen247548
Tipton238123
Unassigned22615
Dyer224732
Gibson217244
Coffee192325
Hardeman190533
Greene181252
Obion179522
Trousdale17768
Bedford174520
Dickson170719
Fayette169825
Anderson169713
McMinn165937
Lawrence164520
Loudon164311
Cumberland161327
Wayne16047
Carter158334
Weakley157326
Jefferson156421
Monroe147228
Warren144910
Lauderdale144117
Henderson142126
Hardin140420
Macon134825
Roane13217
Franklin130220
Haywood129728
Overton122917
Hawkins122625
White119414
Johnson11577
Marshall115710
Carroll115326
McNairy113427
Rhea112418
Cocke108014
Cheatham106911
Campbell103512
Bledsoe10264
Smith99413
Lake9873
Giles98336
Fentress91811
Lincoln9173
Crockett87020
Hickman81015
Henry80211
Marion7839
DeKalb73717
Chester73314
Decatur66311
Grainger6124
Grundy57511
Union5463
Claiborne5286
Polk51713
Humphreys4584
Jackson4535
Morgan4437
Unicoi4333
Houston42317
Benton4219
Cannon4212
Lewis4185
Clay40615
Scott3865
Sequatchie3472
Stewart33611
Meigs3296
Perry3082
Pickett2748
Moore2722
Van Buren2081
Hancock1213

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