New federal guidelines that acknowledged the role of aerosols in the spread of COVID-19 were removed Monday from the website of the Centers for Disease Control and Prevention, which said they had been posted by mistake.
The updated information about coronavirus-laden aerosols, which came to the attention of independent scientists on Sunday, was "a draft version of proposed changes" that had been "posted in error to the agency's official website," according to a notice that was added to the CDC site.
New guidance that clarifies the risk posed by aerosols will be posted once the update process is completed, the notice said.
The reversal threatened to further undermine the CDC's credibility in the midst of a pandemic and renewed charges that the Trump administration is improperly meddling in the agency's scientific process.
A CDC spokesman said the site had been updated "without appropriate in-house technical review." The criteria for making such changes are now under review, he added.
For now, the CDC says the coronavirus mainly spreads from person to person via tiny respiratory droplets that are produced when an infected person coughs, sneezes or speaks. Those droplets may land in the noses and mouths of other people within about 6 feet, potentially seeding a new infection.
The draft guidance added that the virus could also spread through smaller airborne particles, and that these aerosols could travel farther than 6 feet in certain circumstances, including in restaurants, at gyms and during choir practices.
Generally no more than 100 microns in size – less than the average diameter of a human hair – aerosols are light enough to remain suspended in the air. That means it would be risky to spend time in indoor areas without proper ventilation, the draft said.
Although virus-laden droplets and aerosols could land on surfaces that are touched by others who then touch their own nose, mouth or eyes, this is not considered a primary way the virus spreads, according to the draft, which bore Friday's date.
Independent researchers said Monday that they were confused by the sudden reversal.
"I don't know if it was an honest mistake or if it's political influence," said Linsey Marr, an environmental engineer at Virginia Tech and an expert on airborne transmission of viruses.
"I would like to see the website reflect the best available scientific evidence, which is that COVID-19 commonly spreads through inhalation of aerosols, and this means that we need to wear masks even when we're farther than 6 feet away from other people, and we need to ensure that our buildings have good ventilation," she said.
If approved, the draft guidelines would constitute a major shift in the CDC's understanding of the virus that has claimed almost 200,000 American lives, and how it spreads. It would also mean that the agency's current advice to stay 6 feet away from others and to wear a mask that covers the nose and mouth wouldn't be enough to stop the virus from spreading.