Social Distancing Isn't Enough to Prevent Infection - How to Detect COVID-19 Super-Spreaders

[orangecrush]

Social Distancing Isn’t Enough to Prevent Infection – How to Detect COVID-19 Super-Spreaders



“My work has shown that exhalations are not isolated droplets but in fact come out as a turbulent, multiphase cloud. This gas cloud is critical in enhancing the range and changing the evaporation physics of the droplets within it,” said Bourouiba. “In the context of respiratory infectious diseases, particularly now COVID-19, this work underscores the importance of changing distancing and protection guidelines based on fluid dynamics research, particularly regarding the presence of this cloud.”

Bourouiba presented examples from a range of infectious diseases including COVID-19 and discussed the discovery that exhalation involves different flow regimes, in addition to rich unsteady fluid fragmentation of complex mucosalivary fluid. Her research reveals the importance of the gas phase, which can completely change the physical picture of exhalation and droplets.

Nordic Institute for Theoretical Physics scientist Dhrubaditya Mitra and his team realized they could use the mathematical equations that govern perfume to calculate how long it would take for viral droplets to reach you indoors. It turns out: not very long at all.

“
Perfume worn by someone at the next table or cubicle reaches your nose thanks to turbulence in the air. Fine droplets spewed by an infected person spread in the same way. The researchers found that below a relative distance known as the integral scale, droplets move ballistically and very fast.

Even above the integral scale, there is danger. Consider an example where the integral scale is two meters. If you were standing three meters — just under ten feet — from an infected person, their droplets would almost certainly reach you in about a minute."


https://scitechdaily.com/social-distancing-isnt-enough-to-prevent-infection-how-to-detect-covid-19-super-spreaders/



Fascinating reading.

[Ms. Toad]

1. That's why it has always angered me when I hear people who should know better say

Wear a mask when you can't socially distance.

It's not OR, it's AND. Wear a mask AND socially distance.

Social distancing reduces the chance that the droplets will reach you; wearing a mask provides added protection from the aerosolized particles that keep swirling around in the air for up to hours, and for smaller number of droplets that travel farther than 6'.

[NYC Liberal]

2. Yep and people here said it was totally fine when thousands of

crowded into the streets after Biden won because they had masks on. Well, it wasn’t.

[Ms. Toad]

3. Most of us get stupid and careless.

Which leaves the rest of us paying the price - in fewer health care resources, by having to mask in our own homes, and by getting sick becuase even the double-mask I wear to sleep isn't 100% protection from family members who keep taking risks they think are small.

[moonscape]

9. Yikes. You sleep in 2 masks? You can't

isolate in a room? I am so sorry for whatever circumstances make this necessary

[Ms. Toad]

11. Unfortunately,

I had a hard conversation with my spouse and daughter two and a half weeks ago. The upshot of that was that they cannot/are not willing to wear masks with (1) family we don't live with, (2) coworkers, or (3) a "small" social circles - all of which are the main driver of the current surge.

Both believed they were relatively safe. I begged, pleaded, guilt-tripped them, to no avail - because I know that each of the other people around whom they are being unmasked are also being similarly careless around others. (For example, a family party in July was advertised as mask required, family only - it turned out to be not much family and no one masked. My spouse's sister arrived in a mask, asked the first stranger she encountered if he had COVID, he said no, so she said, "Whew" and whipped off her mask. Within a week of that time she flew across the country, back, and hosted a shower for other family members. She, and another sister with whom she does not live drove to Tennessee for Thanksgiving with another relative. So when my spouse tells me everyone she takes her mask off around is careful - I know their definition of careful does not match mine.)

So to keep myself safe, I started wearing a mask at hom 24/7.

That same day, my spouse's co-worker came into the office to pick up mail. He had been experiencing symptoms for several days, and his wife had tested positive. (She didn't overlap with him - but she was in later that day without any cleaning routine. Three days later my daughter's "small" social circle included a woman who was symptomatic and who tested positive. She was unmasked around her the better part of two days.

Overnight is the most breathing in the same room with my spouse. We run an air purifier with a HEPA filter that filters to .3 microns and clears a room twice the size of the bedroom 4x an hour - which (in theory) removes 95+% of the virus. The other alternative is sleeping in my recliner. It's probably a toss-up as to safety (since air circulates in the entire house & my recliner is in a much larger room, making it harder to clear with the purifier), and my bed is more comfortable.

Fortunately, I'm off quarantine tomorrow (imposed by my work because my daughter was exposed). That means I can have several hours a day at work without a mask (I have an office so I can be unmasked in the office as long as no one else is there with me).

I'm pissed - but no good alternatives without renting someplace else to live for the duration. My spouse has promised to wear a mask until there is a vaccine - but since she told me she was wearing one all along until very intense, detailed questioning fleshed out that always doesn't mean always - I will need to regularly question her to feel safe, and that takes more energy than just wearing a mask 24/7.

Incidentally - since I've started being very vocal about it I have encountered a number of other people whose families differ about risk tolerance It is ALWAYS the person who is being most diligent about safety who pays the price (either in tolerating heightened realistic concern about expousre - or - in being burdened by needing to treat their home as a public space).

[moonscape]

12. Quite a story. Thanks for telling it. There are no

perfect ways to negotiate or navigate it, but am glad you didn’t throw up your hands and are instead doing what you can to stay as safe as you can. The renting of a small place for a while would be very tempting, I must admit.

I remain baffled by all those who aren’t being personally vigilant, for themselves and each other, but that’s an unsolvable mystery.

[Crash2Parties]

6. Outdoors is a different story altogether

Multiple studies have shown that the BLM protests & similar outdoor events have NOT resulted in measurable COVID spikes. There is no reason to assume that the Biden celebrations were different.

Indoors of course is an entirely different story.

It's all about how many viruses a person inhales or encounters with their mucus membranes (eyes, nose, etc.). And that in turn is highly dependent upon airflow.

[NYC Liberal]

7. It's still completely irresponsible when we're still learning about this virus.

And even outdoors, you still need to maintain distance, which was not happening.

[certainot]

15. rw media kept saying dems hypocritical to complain about their protests because what you said

but those dumbshit trump gatherings have a lot less masks

nevertheless any gatherings are risky

see also Crash2Parties

[FM123]

4. Good article. K & R

[orangecrush]

18. Thanks

[Klaralven]

5. Also -- keep your mouth shut

To better understand droplet dynamics in the COVID-19 pandemic, a team from Northwestern University and the University of Illinois at Urbana-Champaign tested the capacities of a new wearable device. The thin, wireless, flexible sensor attaches like a sticker to the bottom of the neck to capture vital signals. Ongoing clinical studies are using the device with hospital patients.

The team found that the device distinguishes between coughing, talking, laughing, and other breathing activities with its machine learning algorithms. Researchers used particle tracking velocimetry and a decibel meter to analyze droplets produced by device wearers.

“Different types of speech can generate drastically different numbers and dynamics of droplets,” said biomedical engineering researcher Jin-Tae Kim, who led the investigation.

Normal exhalation through the nose produces far fewer droplets than vocalization with an open mouth. Loud talking, shouting, singing, etc. are especially bad.

[Greybnk48]

8. Everyone should be wearing a shield, protective glasses, or just plain glasses as well,

since the virus can enter the mucous membranes of the eyes.

[Duppers]

14. Very good advice.

[certainot]

16. my sunglasses are too dark for me for shopping so i started wearing my blue light glasses which

are clear but don't magnify. but there are more gaps than with face shield or eye protective goggles.

[Initech]

10. So basically don't go out of your house and if you do, wear a helmet around your face. Got it.

[Ms. Toad]

17. Your house is not safe either,

Unless everyone you live with is taking the same precautions. Have a detailed conversation with those you live with, and take appropriate steps to protect yourself.

[IthinkThereforeIAM]

13. Bars are busy in South Dakota...

... I came home from a quick in and out shopping trip about 9 pm, and the three bars on the two block long main street here just outside of Sioux Falls were busy judging by the number of cars parked on main street and the off the street lots.

What was it about Frank Luntz and the messaging thingy, again? Right.

[ProfessorGAC]

19. The Fluid Dynamics Are Conceptually Solid

One thing I'd disagree with a bit, though, is that turbulence falls exponentially with the increase in volume. In fluid dynamics, there is a threshold U value that is required to create turbulent flow. As the volume increase, velocity falls and U drops below the threshold into laminar flow.

My math suggest that the 3 meters in one minute is exaggerated a bit. I think at some point, gravity starts to overcome eddy effects, and the droplets remaining begin downward. I'm not seeing the mucosa/viral concentration at head level they suggest.

Now, being seated when others 10 feet away are standing changes the scenario.

My other "hmmm" is the use of the perfume model, given the organic compounds giving perfumes their scent are volatile at body temperature and in a true vapor state, even down to 20-30°F.

The droplets are only in the vapor state at very near distance from the droplet surface. Once equilibrium is achieved, the vapor concentration becomes a constant.

Yes, turbulence affects the equilibrium, but I take some issue with how long the turbulence actually continues.

All that said, I agree with the post above that it should be masks AND 6'. Unmasked distancing should be much greater.

Given a cough can easily spray 12 feet, and a sneeze well over 20, the unmasked safety range should be at least 15'.

At this point though, anything that changes behavior, no matter how imperfect, is a good incremental improvement.

[Ligyron]

23. Wonder if tall people get sick less often?

[ProfessorGAC]

24. Very Tall? Maybe

5 or 6" taller than average doesn't mean much. The fluid expansion happens because the exhaled air is likely 10-30° warmer is substantial.
Easy to envision a 12" radius bubble at a couple feet. As the temperature equilibrates, the expansion slows until it stops.
The turbulence after that is more caused by environmental air flow.
So, I could see a 7' person being safer, but that doesn't mean safe.

[smirkymonkey]

20. Kicked and bookmarked!

[shanti]

21. Medical masks

the basic ones, are the only ones I've been using. I finally did buy an N95 mask, but it was pricey!

[Poiuyt]

22. From what I understand, your chances of geting Covid are dependent on concentration of the virus and

length of time that you're exposed. The further you are from the source, the more it will have dissipated. Now, if you're with an infected person for any length of time, your chances of getting infected increase. If you're outdoors, where the virus will have dissipated, and you don't spend time talking to an infected person for a long time, you'd have less of a chance of getting infected.

FWIW, I'm retired so I don't go anywhere other than essential shopping. If I find I can't avoid being close to someone in the grocery store (for example), I just hold my breath until I'm in the clear. I know it's not perfect, but it's the best I can do.

[LAS14]

25. Two things: Viral load and viability.

1 - The mere presence of the virus does not mean you can bet infected. There has to be enough of it. There might not be enough in the clouds studied here.

2 - Almost all such studies use a technique that can't distinguish between live and dead virus particles.