The Centers for Disease Control and Prevention updated its COVID-19 guidance to acknowledge the risk that the coronavirus can be transmitted through airborne respiratory particles — but then edited its website again Monday morning to take that information down, saying it was still being reviewed.
Before it was taken down, the updated guidance said the coronavirus is most commonly spread "through respiratory droplets or small particles, such as those in aerosols," which are produced when an infected person coughs, sneezes, sings, talks or even just breathes, and which can remain airborne for a period of time. The virus can then spread to other people who inhale it into their airways.
Many scientists and health experts have been warning for months that COVID-19 can spread through airborne respiratory particles, not just through larger droplets from an infected person coughing or sneezing nearby.
"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's updated, but then deleted, guidance said. "In general, indoor environments without good ventilation increase this risk."
But on Monday, the CDC updated the page again to remove the information about the risk of airborne transmission, with a disclaimer at the top: "A draft version of proposed changes to these recommendations was posted in error to the agency's official website," the notice read. "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 page still states that the virus is spread "through respiratory droplets produced when an infected person coughs, sneezes, or talks," but the information about tiny airborne droplets, like those in aerosols, has been removed. The page also no longer lists breathing as a way to transmit the virus.
Instead, the page reads: "These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs." The Monday update also says COVID-19 is primarily spread between people who have close contact (within 6 feet), and includes that it may be spread by people who are not showing symptoms.
In July, the World Health Organization (WHO) acknowledged the airborne transmission of "micro-droplets" as a possible cause of COVID-19 infections. WHO's acknowledgment came after 239 scientists signed an open letter about the risk of airborne transmission.
Very few diseases — tuberculosis, chicken pox and measles — have been deemed transmissible through aerosols. However, Japan, for example, had been operating for months on the assumption that tiny, aerosolized particles in crowded settings were fueling the spread of the coronavirus. Back in February, Japan adopted a strategy to fight airborne transmission of COVID-19 by telling residents to avoid "the three Cs" — cramped spaces, crowded areas and close conversation.
The CDC's guidance also explains that the closer and longer a person with COVID-19 is with others, the higher the risk of spreading the virus to those people.
On Friday, the CDC also updated its testing guidance after nearly a month of controversy over the role of political interference from officials at the Department of Health and Human Services overriding the CDC's scientists. In late August, the CDC's website was quietly revised to say that people who had been exposed to someone with coronavirus but weren't showing symptoms might not need testing. That caused an uproar among medical experts because asymptomatic people can easily spread the virus to others.
The new guidance now says, "Due to the significance of asymptomatic and pre-symptomatic transmission, this guidance further reinforces the need to test asymptomatic persons, including close contacts of a person with documented SARS-CoV-2 infection."
Many public health experts have long advised that even asymptomatic people should be tested if they suspect they've been in contact with someone who was infected. In July, a model published by the National Academy of Sciences, showed an estimated 50% of coronavirus cases may be spread by people who aren't showing symptoms.
-Lucy Craft contributed reporting.