Something has really been bothering me a lot and it's the notion that there is a scientific debate about whether aerosol transmission of #SARSCoV2 #COVID19 #coronavirus occurs. I don't think there's any debate. It does.

The problem is that the terminology is used by scientists to mean different discipline-specific things. Epidemiologists talk about patterns of transmission. Infection preventionists talk about PPE. Aerosol engineers talk about physics/fluid dynamics. Virologists talk about dose.

Speaking very generally about my perspective as a virologist, we know that plenty of other "droplet"-borne pathogens, like influenza, can be transmitted by inhalation. The size and behavior of the particles that are inhaled are variable, but we are mostly thinking about the virus

How much infectious virus is in those particles? Where do the particles go in the respiratory tract? What is the receptor distribution like in the respiratory tract? What circumstances allow the virus to find a susceptible host cell?

These questions don't dispute an acknowledgement that aerosol transmission occurs, whether that means by floaty particles or small particles or both. But it's also very difficult to distinguish droplet transmission from short-range aerosol transmission using epidemiological data.

Unfortunately, most of the data we have is epidemiological data that shows transmission by air over a short range. You can't say for sure based on interviewing people and counting cases/contacts if they were infected by short-range aerosols or droplets.

Animal models have shown transmission by inhalation, but it's hard to use those studies to say definitively it's MOSTLY aerosol vs droplet in people in the real world, as opposed to ferrets or hamsters in a ABSL-3 lab. The point is that aerosol probably occurs IRL.

So I'd rather talk about the risks, benefits, and data for aerosol precautions. A common complaint is that we aren't doing enough to take precautions against aerosols, but other than ventilation/filtration, I don't see how the present guidelines change much.

Ventilation/filtration needs are specific to a given space. Not everyone will be able to implement meaningful changes to their air handling infrastructure beyond opening a window and even inexpensive portable filters may be out of reach.

Thus I'd rather emphasize the additive nature of risk reduction. For aerosols, droplets, or fomites, people should implement as many of the following measures as possible:
-Physical distance
-Avoid crowds
-Avoid indoors/enclosed spaces
-Masks
-Ventilate/filter
-Wash hands

This pandemic has been characterized by framing the science categorically, as if all scientific data is binary. It's all aerosol or none of it is. In real life, it's shades of gray. Probably aerosols, droplets, and fomites all mediate transmission, depending on the circumstances.

I'd like to get away from the aerosols vs. droplets non-controversy and start discussing these issues rather than the semantic preferences of one discipline over another. We agree that aerosols can transmit the virus. Let's start clearly communicating the knowledge gaps:

Here are some in virology:
1. We don't know infectious dose (how much virus you have to be exposed to in order to cause an infection)
2. We don't know how minimum infectious dose differs by route
3. We don't know how dose impacts disease severity

4. We don't know how route impacts disease severity
5. We don't know how dose or route impacts tissue tropism
6. We don't know how dose or route impacts functional immunity
7. We don't know if it matters at all if you're infected by short-range aerosol or droplet

So while there are still a lot of open questions, I'd go so far as to say there isn't actually much of a debate across disciplines over whether short-range aerosol transmission occurs and I'd really like it if we could stop fueling this exhausting narrative. /end rant