The experiment that proved airborne disease transmission

For all the talk about how much masks help, I haven't seen great studies that aren't in vitro, not specifically in health care settings, and not specifically around someone known to have it. I found this which is at least a natural experiment:

https://www.healthaffairs.org/doi/pdf/10.1377/hlthaff.2020.0...

> Mandating face mask use in public is associated with a decline in the daily COVID-19 growth rate by 0.9, 1.1,1.4, 1.7, and 2.0 percentage points in 1–5, 6–10, 11–15, 16–20, and 21 or more days after state face mask orders were signed, respectively.

I'm trying to sort of if those percentages are absolute or relative. I think they're absolute because some of the graphs are labeled "percentage point change," but using absolute percentage point changes for an analysis like this is seriously flawed because a 2% reduction could range anywhere from a miracle to statistically significant, but negligible.

It's also not clear if people feel safer wearing face masks, so they engage in riskier activities.

My guess is they're not as effective as claimed because while the Bay Area has pretty high compliance, if masks were systemically very effective, we'd see case rates drop a lot faster, not still be above mid-June numbers. That said, whatever the Bay Area is doing right now is working.

The point of the parents' posts is that you have these issues with ozone even if you just irradiated the air ducts without direct contact to UVC.

Where would it get the carbon-14 from? Virus particles (virions) are made by and from their host. So you'd need a human made from carbon-14 first.

The idea of respiratory viruses not being airborne sounds silly. What's the viral charge supposed to do, not jump into droplets smaller than certain size?

Of course they are present in the smallest droplets! They are present in the mucous secretions of the infected individual and they will get expelled through the big and the small droplets.

The distinction shouldn't be a qualitative one, airborne vs not airborne. It's a quantitative one, sufficiently infectious viruses may pose a risk at much smaller doses, the kind that you may be exposed by the smallest droplets expelled that simply stay afloat.

It's also worth noting that human immune response is a complicated beast, what may not be infectious for an average healthy individual may put down someone with a weakened immune response. So even supposedly "not airborne" viruses that are very unlikely to infect the average healthy individual at very small doses may pose an "airborne" risk for individuals with a weakened immune response.

There are more factors in all of this, atmospheric conditions may play a role. For example, cold temperatures may be more suitable for the virus to remain infectious outside of a host, thus increasing the likelihood of "airborne" propagation.

TL;DR: The distinction between airborne and not airborne viruses is an artificial one. That only makes sense statistically for an average individual at certain atmospheric conditions for a concrete strain of the virus. But as any real-world statistical distribution there are tails and you will find "airborne" qualities for pretty much any respiratory virus in those tails.

The amount of heat in the air is small compared to that in other materials; buildings with stone or concrete walls have a sufficient heat capacity that you can ventilate without temperature changing too much. This works less well for buildings with wooden walls though.

Ventilating properly requires discipline though. No tilted/semi-opened windows for prolonged time for example. In winter, heating should be turned off and the windows should be as wide open as possible to minimize the time to exchange air. That's to reduce the loss of heat. 5-10 minutes of ventilating is good enough, usually. We usually don't have air condition here, so I don't know what's the recommended process in the summer.

It's common to ventilate like this in Germany in the winter for example. I know (now returned) former German expats that completely missed this development. They still tilt windows and let the heating run all day long.