The information reiterates, however, that “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 also spread the virus to others.”
In a statement to the media, the CDC said, “Today’s update acknowledges the existence of some published reports showing limited, uncommon circumstances where people with COVID-19 infected others who were more than 6 feet away or shortly after the COVID-19–positive person left an area. In these instances, transmission occurred in poorly ventilated and enclosed spaces that often involved activities that caused heavier breathing, like singing or exercise. Such environments and activities may contribute to the buildup of virus-carrying particles.”
“This is HUGE and been long delayed. But glad it’s now CDC official,” tweeted Eric Feigl-Ding, MD, an epidemiologist and health economist at Harvard University, Boston on Oct. 5.
The CDC announcement follows an abrupt flip-flop on information last month surrounding the aerosol spread of the virus.
Information deleted from website last month
On September 18, the CDC had added to its existing guidance that the virus is 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 be inhaled into the nose, mouth, airways, and lungs and cause infection.”
The CDC then deleted that guidance on Sept. 21, saying it was a draft update released in error.
A key element of the now-deleted guidance said, “this is thought to be the main way the virus spreads.”
The information updated today reverses the now-deleted guidance and says aerosol transmission is not the main way the virus spreads.
It states that people who are within 6 feet of a person with COVID-19 or have direct contact with that person have the greatest risk of infection.
The CDC reiterated in the statement to the media today, “People can protect themselves from the virus that causes COVID-19 by staying at least 6 feet away from others, wearing a mask that covers their nose and mouth, washing their hands frequently, cleaning touched surfaces often, and staying home when sick.”
Among the journals that have published evidence on aerosol spread is Clinical Infectious Diseases, which, on July 6, published the paper, “It Is Time to Address Airborne Transmission of Coronavirus Disease 2019,” which was supported by 239 scientists.
The authors wrote, “there is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (microdroplets) at short to medium distances (up to several meters, or room scale).”
Aerosols and airborne transmission “are the only way to explain super-spreader events we are seeing,” said Kimberly Prather, PhD, an atmospheric chemist at the University of California at San Diego, in an interview Oct. 5 with the Washington Post.
Dr. Prather added that, once aerosolization is acknowledged, this becomes a “fixable” problem through proper ventilation.
“Wear masks at all times indoors when others are present,” Dr. Prather said. But when inside, she said, there’s no such thing as a completely safe social distance.
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