Airborne Transmission of SARS-CoV-2 Delta Variant in Tightly Monitored Isolation | Hacker News Reader

Airborne Transmission of SARS-CoV-2 Delta Variant in Tightly Monitored Isolation

wwwnc.cdc.gov

38 pointsDrScump15 comments

So much for fomite theater.

Early on at least one cruise was tied up in Japan while the passengers were confined to their cabins while the HVAC system spread the virus around.

Yep, it's aerosols and I'm sure happy I have had three shots. Hopefully the shots and vitamin D will get me through omicron which will likely come to all of us.

It's more of a confirmation thing, I think. We've been pretty sure about Covid being airborne since early 2020. This probably helps convince some of the few that insist it isn't.

The entire basis for wearing surgical masks and cloth masks is droplet transmission.

They don’t help at all with aerosol transmission.

So basically the entire world is crazy to mandate it unless it’s minimum kn95 or n95 masks.

Many many people don’t want to accept its aerosol transmission because it means it’s much harder to do anything about it.

https://www.nature.com/articles/s41598-020-72798-7

"Here, we measured outward emissions of micron-scale aerosol particles by healthy humans performing various expiratory activities while wearing different types of medical-grade or homemade masks. Both surgical masks and unvented KN95 respirators, even without fit-testing, reduce the outward particle emission rates by 90% and 74% on average during speaking and coughing, respectively, compared to wearing no mask, corroborating their effectiveness at reducing outward emission."

>Surprisingly, wearing an unwashed single layer t-shirt (U-SL-T) mask while breathing yielded a significant increase in measured particle emission rates compared to no mask, increasing to a median of 0.61 particles/s. The rates for some participants (F1 and F4) exceeded 1 particle/s, representing a 384% increase from the median no-mask value.

Double cloth had a higher but not statistically significant increase in particle count (so equivalent to being unmasked) while vented N95s reduced particle surprisingly well.

It says single layer cloth there, not double :)

What I did strange is that the cloth masks are mostly stuffier and harder to breathe than the surgical ones, which filter much better.

The FFP ones are of course the worst to use but also the best at filtering.

Either way I can't wait till we can safely get rid of all of them though... I wish there were powered ones with fans to pull in filtered but fresh air. But the only one I've seen is the Razer Hydra and it's always out of stock. It's also huge and looks like a WW2 gas mask so it's not really street smart.

The study included single and double layer; both were an increase vs no mask, but only single was statistically significant.

>"...outward particle emission rates..."

That's outward transmission when the wearer is already infected, which has nothing to do with mask protection of the uninfected.

Of course it does: if the recipient is uninfected, and if they are already infected then it doesn't matter.

Clearly you aren’t in the Netherlands, where the authorities only started advocating adequate ventilation a few months ago. Before that washing your hands was more important.

Recent media article: https://www.mercurynews.com/2021/12/30/covid-travelers-infec...

"COVID: Travelers infected one another across hallway, research shows"

What people don't get is the simple math of masks. For example, a 70% filtration-rate mask (let's say, surgical one) is not just 25% worse than an N95 mask - it's actually 5 times worse. And an N95/FFP2 is not just 4% worse than an N95/FFP3 one - it's 5 times worse. Also, things are drastically changing with Omicron - an N95 may not be enough to protect you during a prolonged exposure. If you use the above math, you will see that going to work 22 days a month and spending 8 hours a day with an N95 mask is equivalent to being without a mask for more than a day during that month.

N99/FFP3 masks usually have valves, making it them inappropriate for covid. And in the end, fit is more important than the filtration rate. The 95% rate of N95 is actually a minimum, it is likely much higher for actual virus-containing aerosols, but if air leaks from the sides, it becomes much lower.

If you think you need better than N95, you will probably want a full face mask with HEPA filters.

3M offers FFP3 masks without valves [0]. I found a couple more companies with disposable FFP3 masks, but none with N99 certification. I managed to buy EGE masks (made in Turkey, but certified in EU) [1] when I was in Bulgaria and they were less than $2 a piece. The other part of the math of masks is that a $2 FFP3 mask is actually cheaper than a KN95 mask, which has a shorter lifespan.

[0]: https://www.3m.com/3M/en_LB/p/d/v101158114/

[1]: https://www.egemaske.com/ege-700-ffp3-nr/ege-700-ffp3-nr-d.h...

This also suggests that a tight fitting mask can make a difference between inhaling it or not.

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