This scientist made a Google Doc to teach the general public about airborne coronavirus transmission


Why did you make this document instead of going down the traditional science publishing route?

Science publishing is very slow. For the scale of the pandemic, people need information today. And publishers can be cryptic. They all have their own rules. In reality, you can only publish things that have not been published before, so it’s not a good way to answer questions from the public. And crucially, it needed to be updateable so we can answer people’s questions as they come. In a journal, it would be frozen.

What have been your main frustrations with the response to the evidence around airborne transmission?

Ever since we wrote that letter, signed by 239 scientists, I have been waiting for the landslide. The evidence is now simply overwhelming that the virus is spread through aerosols. The idea it’s mainly droplets is a myth. It’s an error from 1910 made by Charles Chapin, who wrote a book called The Sources and Modes of Infection. In that book, he associated the risk of infection with droplets. He said, admitting later it had been without evidence, that aerosol transmission is almost impossible, and anyone who says otherwise has to prove it. And that has become dogma ever since. It’s almost a superstition. To this day it’s still what the CDC says.

I’m still waiting for that landslide, where suddenly everyone moves and there’s a huge change. But it hasn’t happened yet. Germany has started saying that good ventilation is the cheapest and best method to reduce the spread of the virus—and that only makes sense if you think it’s mostly spread by aerosols, not droplets or surfaces. The CDC published some guidelines which were confusing, which said inhalation is the main way it spreads—and that means aerosols, as only they can be inhaled—so they were admitting aerosols were the main mode of transmission. Then they took it down. We don’t know if it’s because of politics or dogmatic scientists who refuse to let go of droplets.

Aerosol transmission is the main way this virus spreads: the only question if it’s 70%, 80%, or 90%. Ballistic droplets are a negligible way to spread the virus. They only spread if someone coughs or sneezes on you. They drop to the ground, whereas aerosols linger. If you look at superspreading events, for example the Washington choir case, it is impossible they are being spread by droplets. For 52 people to get infected, it has to be by aerosols. If droplets were important, it would matter less if you are inside or outside, and you’d expect transmission to happen a lot more outdoors. But if you go outside, transmission drops tremendously. The evidence is clear. It’s scandalous and absurd these agencies refuse to give correct guidance.

What are the most important parts of the document to understand for personal safety?

The thing people need to understand is aerosol transmission is like everyone breathing out cigarette smoke, and you want to breathe in as little of others’ as possible. Everyone you are around, imagine they are breathing smoke, and try to avoid it. It’s not good enough to just give people guidelines; you need to explain the actual science behind it, too.

The second most important thing is the recommendations section—how to interpret the science for any given situation. Avoid anything that involves breathing in a lot of other people’s breath. Do things outdoors. But the most important things are free. Wear the mask you already have when you are inside public spaces, and open a window. If we did those, transmission would go down dramatically. Things like ventilation and air filtering matter, but the main things we can do cost nothing.

And finally, perhaps not for the general public but for people who want to understand how we got here—look at the history, in section 1.3 and 1.4 of the document. It is critical, and it explains why the WHO and CDC are not budging. I wonder what percentage of the global population we could reach with our advice. We’ve reached millions, but it’s still a tiny fraction. And if the CDC, WHO, and local health agencies don’t change their guidance, it really defeats the purpose. It makes me so angry.


Steven Gregory