COVID-19: Airborne or Not?

Posted: March 19, 2020 in COVID-19
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When a virus is airborne, it means virus-laden particles are floating in the air. If someone becomes infected by breathing in these particles, they caught the virus by “airborne transmission.”

Virus particles eventually fall out of the air and land on near-by surfaces. Most end up on the ground, but some land on desktops, countertops, and tabletops. If someone touches these contaminated surfaces, their hands become “loaded” with virus particles, waiting to be transferred to anything they touch—another desktop, a doorknob, the phone. When you touch a contaminated object, then touch your eyes, mouth, or nose, you could become infected by “respiratory droplet”.

All respiratory viruses are briefly airborne, but most fall quickly out of their clouds (including seasonal influenza and most colds). These infections are primarily caught by respiratory droplets on surfaces. Most importantly, respiratory droplet infection can be prevented with good hand washing, particularly when combined with surface/object cleaning and disinfection.

But a few viruses—notably measles and tuberculosis—remain airborne for a long time. If an infected person stays in one place, the air around them slowly fills with virus particles, eventually extending wider than their 6-foot cloud.  The longer they sit and the smaller the room, the more virus ends up floating in the air. The virus can even drift around the room for several hours after the infected person leaves.

As you can imagine, airborne viruses are much more infectious than those that infect via respiratory droplets. If you spend a prolonged time in a room either with or after an infected individual, you might become infected simply by breathing. The only prevention? Infected patients must wear masks to catch the virus before it enters the air.

Is COVID-19 airborne?

This is the million-dollar question. Is COVID-19 transmitted like seasonal flu or like measles? The World Health Organization and the CDC have insisted since the beginning that COVID-19 is transmitted only by respiratory droplets. Worldwide response has been based on this principle.

But scientists and physicians have questioned this. We know people in prolonged close contact with each other (household contacts, nursing home residents, and cruise ship participants, for example) show much higher infection rates than the general population—the expected pattern from airborne transmission. Yet officially, these occurrences are attributed to too many shared surfaces and inadequate infection precautions—touching things with not enough hand washing, cleaning, and disinfecting.

And we’re learning that healthcare workers also become infected at alarmingly high rates—another close contact group. Yes, they are exposed to many more infected patients than everyone else, but they are also much, much better at following infection control guidelines, particularly when it comes to handwashing. It’s been drummed into us for years!

What healthcare workers lack is a way to prevent airborne infection. That requires three things: 1) a way to identify infected patients 2) rooms with specialized air filtration systems for infected patients, and 3) masks for both infected patients and healthcare workers. All three of these things are in very short supply during the COVID-19 pandemic.

Two days ago, the first study was released on how long COVID-19 virus remains alive on surfaces and in the air. And guess what? They found some virus particles still airborne after three hours! The number fell markedly over the three hours, but it was still there.

What Does This Mean For You?

Based on infection patterns, and supported by the study, COVID-19 might have significant airborne transmission, although there is no official acknowledgement of this. What does this mean? It still comes down to “Pigpen” clouds. You just have to imagine much larger clouds whenever people spend a prolonged time in “small” enclosed spaces. Their clouds might even fill the room.

How small is small? Until someone does the research, I can only guess. Anything the size of patient care rooms or nursing home bedrooms makes me nervous. I don’t know about conference rooms, shared workspaces, or smaller retail outlets, but I’m glad regulations are starting to limit their use.  And I feel pretty good about large spaces like pharmacies, grocery stores and warehouses.

How long is prolonged? Again, I can only guess, but an infected person probably has to spend an hour or more in an enclosed space to start filling it with virus. Otherwise, they are just a cloud passing by. Similarly, your odds of breathing in the virus increase the longer you stay in the room.

I suspect you can go freely in and out of smaller shared spaces in your community—just don’t spend more than 15 minutes in one. (If your work requires you do so, push for changes as soon as possible, before infection numbers climb higher.) You can also spend as much time as needed in large spaces as long as you practice good hand washing.

The tricky question is shared spaces in your living environment. But that will have to wait for another blog post.

Stay healthy.

  1. Allan Bell says:

    Thank you for all of your research and Information. I appreciate you and Brett on the 529 nets.

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