On October 5, the Centers for Disease Control (CDC) updated its guidance on how COVID-19 is transmitted between people. The major takeaway? In certain instances, there is potential for airborne transmission.
“But wait,” you say. “Didn’t we always know this virus was spread through the air?” If this CDC update has you scratching your head in confusion, never fear. We asked Saskia Popescu, Ph.D., infection prevention epidemiologist and member of the Federation of American Scientists COVID-19 task force, to clarify what “airborne transmission” really means.
How COVID Spreads
Since the early days of this pandemic, we’ve all heard the social distancing refrain: Stay six feet apart from anyone outside your household. This isn’t an arbitrary number. Six feet is the recommended distance to avoid passing respiratory droplets to one another, those particles inside your nose and mouth that may contain traces of live virus.
This is called “droplet transmission,” and it remains the predominant way COVID-19 is spread. “The primary route is close contact,” Popescu says. The virus also spreads through direct personal contact, i.e. drinking from someone else’s water glass or touching a hand they’ve sneezed into.
In recent months, experts have learned more about COVID-19 from studying super-spreader events and tracking cases across the world. One thing they’ve noticed is that social distancing (on its own) isn’t a perfect solution. Now, we know the reason for this—the virus can linger in the air through tiny particles that float through space. This is called “airborne transmission.”
“Ultimately, this means that in high-risk environments, such as crowded indoor spaces with poor ventilation, there have been instances of airborne transmission, and the six feet apart rule didn't really apply,” Popescu explains. “Distance is important, but often people would think that just because they were apart indoors with other people, they could remove their mask.”
The risk of transmission does decrease the further away you are from someone, since droplet transmission is still the most likely method of spread. Transmission risk also decreases significantly in outdoor spaces (versus indoor spaces, where trapped and circulating air can linger for hours). The CDC notes that airborne transmission of COVID-19 only happens in special circumstances, like situations where a contagious person spends prolonged time in poorly ventilated air.
What This Means for You
In practical terms, this update doesn’t change the known precautionary measures. “This really doesn't change much,” Popescu says. “You still want to avoid crowded indoor spaces, and really, if you're inside with folks outside your household, you should be wearing a mask.”
What it does confirm is that masks are always important, even if you are six feet apart from everyone else. This is especially true in indoor gatherings, where airborne spread of COVID-19 is more likely.
So, before you head to the grocery store, mask up! Even if it’s not crowded inside, you want to minimize your chances of exposure to the virus—through a sneeze, a cough, or in the circulating air.