Outdoor air and Corona Virus infections

[Chuckanut]

Here's a blog entry by Cliff Mass who teachers Atmospheric Sciences at the University of Washington. See the June 30, 2020 entry.

https://cliffmass.blogspot.com/2020/06/the-safety-of-outdoor-air-for.html#comment-form

Keep in mind that while Dr. Mass is rational scientist he is not a specialist in epidemiology. On many controversial subjects (like climate change) he has been known to get both sides upset with him when he calls out bad science and irrational thought processes.

There is now powerful observational evidence that outdoor air is extraordinary safe regarding COVID-19, and the recent protests have helped provide it. The protests/riots began in Seattle and other cities on May 26th. Thousands gathered without social distancing and a good 10% had no masks. They participated in chanting, singing, screaming and other activities that ensured plenty of droplets were injected in the air, and that unhealthful environment was "enhanced" by coughing from tear gas and other agents.


Did this huge exposure result in increased spread of COVID-19? The answer is clearly no.

The lack of outdoor transmission is consistent with the scientific literature. There is in fact no documentation of effective outdoor transmission of coronavirus (see my earlier blog for documentation). Some examples of scientific papers discussing the issue, include:

Qian et al., 2020: Examined 1245 confirmed cases in 120 cities in China and identified only a single outbreak in an outdoor environment, which involved two cases.


Nishiura et al., 2020: Transmission of COVID-19 in a closed environment was 18.7 times greater compared to an open-air environment (95% confidence interval).

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[audreyh1]

Good to know.

It should be obvious by know if outbreaks correspond to protest cities, but from what I have read hardly any cases are linked to those outside gatherings at all.

 

[Aerides]

However... there's this - an outdoor dinner party resulting in several infections:

https://people.com/human-interest/c...ite-alleged-party-guests-get-covid-19-report/

While it makes sense that outdoors is far safer than indoors, standing around unmasked with another person in close proximity, in or out, is still a risk.

 

[sengsational]

I'll remain unconvinced. Why? Because there's only a handful of indoor transmission cases documented too. And it's easier to gather evidence for indoor events (you at at that restaurant that night, or not...easy to ID the people). How do you ID the people that were in a few city blocks over a period of a few days? That's a harder problem, so the correlation doesn't just fall out of the data. I certainly agree that it's less risky to be outside, maybe even by an order of magnitude, but that might not be safe enough for everyone.

 

[Starsky]

A friend made an excellent analogy - think of how far away you can smell a cigarette. That's not dissimilar to how someone's breath will spread out.

It freaks me out to be walking with a mask, and having mask-less joggers run by me huffing and puffing...and then walking through their germ cloud. It happens frequently during every walk. (I never thought I'd be such a germaphobe!)

I can't go for my usual walks anymore and have started to use the in-between alleys to stay away from people.

 

[sengsational]

True. On my recent camping trip, I noticed that the vape exhale didn't get immediately sucked into the campfire updraft as fast as I thought it would. Not my vape exhale, of course, but our youngest couple on the annual camping trip does have that vice. But I watched those clouds go around other people's heads and thought....hmmm.

 

[timo2]

However... there's this - an outdoor dinner party resulting in several infections:

https://people.com/human-interest/c...ite-alleged-party-guests-get-covid-19-report/

While it makes sense that outdoors is far safer than indoors, standing around unmasked with another person in close proximity, in or out, is still a risk.

Mere cloth masks that only limit the spread of people's spit are starting to look fairly effective, even at screaming and shouting protest rallies. Perhaps the police strategy of keeping the crowd moving helped limit the virus loads also? The outdoor is just an enhancing factor.

Recall that hair stylist in Springfield, MO where the stylist and customers were all masked. The follow up was not 100% thorough, but the people that were randomly checked were negative. Compared to the various no mask, no movement rallies and church gatherings and backyard fêtes, and I think we have a pattern: wear a face covering and don't stay in one spot for hours and hours.

 

[Sojourner]

A friend made an excellent analogy - think of how far away you can smell a cigarette. That's not dissimilar to how someone's breath will spread out.

I don't think that's a good analogy, actually. Cigarette smoke is composed of vapors and gaseous particles that are much, MUCH more microscopic and "airlike" than the small, wet droplets that people emit when they're talking loudly or coughing, etc. For example, it's easily possible to smell/inhale cigarette smoke from a smoker standing dozens of feet away, yet there's virtually no way you could inhale wet, infected respiratory droplets that someone coughs out from that distance. The particles are much too wet and "heavy" to travel those kinds of distances.

Another way to think about this is to consider how a mask would work with cigarette smoke vs. a cough. If you were to exhale a lungful of cigarette smoke while wearing a mask, I'd bet that most people standing 10 feet away would easily be able to smell (i.e., inhale substantial amounts of) that smoke. But if you were to cough heavily into the same mask, probably no one standing nearby would be able to inhale the respiratory droplets from your cough. Those droplets, even though quite tiny, are MUCH heavier and wetter than smoke particles and would be trapped by the mask.

 

[jollystomper]

Good to know.

It should be obvious by know if outbreaks correspond to protest cities, but from what I have read hardly any cases are linked to those outside gatherings at all.

There has been an assumption that everyone at the protests is local to the protest cities. There is the possibility that a lot of protesters came in from outside of the cities, and the people actually in thse cities tended to hunker down. The hotspots might not be in the protest cities, but in the places the protesters returned to. I just do not know if anyone has looked at this is more detail - it is difficult to "trace" the protesters.

 

[ugeauxgirl]

It certainly makes sense in that many of the hotspots are currently in the south, which is miserably hot. People are inside enjoying the AC. At the beginning of the virus, the hotspots were in cold places. (Except new Orleans). Winter is a great time to be outside in the deep South.

But no one really knows at this point- just because it sounds logical doesn't mean it's true.

 

[audreyh1]

I'll remain unconvinced. Why? Because there's only a handful of indoor transmission cases documented too. And it's easier to gather evidence for indoor events (you at at that restaurant that night, or not...easy to ID the people). How do you ID the people that were in a few city blocks over a period of a few days? That's a harder problem, so the correlation doesn't just fall out of the data. I certainly agree that it's less risky to be outside, maybe even by an order of magnitude, but that might not be safe enough for everyone.

People passing each other on the street - unlikely for transmission.
People sitting/standing together talking, laughing, yelling, etc. for 30 mins or much longer - more likely transmission. They can look at these outdoor social or other purpose group gatherings.

 

[audreyh1]

There has been an assumption that everyone at the protests is local to the protest cities. There is the possibility that a lot of protesters came in from outside of the cities, and the people actually in thse cities tended to hunker down. The hotspots might not be in the protest cities, but in the places the protesters returned to. I just do not know if anyone has looked at this is more detail - it is difficult to "trace" the protesters.

But since protests were so widespread, its likely most attendees were from the same state. I would expect someone to already point out correlations if it had a big impact.

 

[Chuckanut]

We had one famous example of a church choir that practiced indoors with 6 feet social distancing. IIRC, about 75% of the singers got the virus, some seriously. One died.

Nothing like that bad happened with the outdoor protesters or that Pool Park crowd in Missouri. I don't wear a mask when walking in uncrowded areas. If an area looks crowded I don't walk there or escape, ASAP. When I see a runner or other person approaching me closely and I cannot step away, I hold my breath and exhale slowly as I pass them. Every little bit helps to reduce the viral concentration one is exposed to when near other people. Keep it low enough and the body can kick the virus's behind before it gets infected.

 

[explanade]

People passing each other on the street - unlikely for transmission.
People sitting/standing together talking, laughing, yelling, etc. for 30 mins or much longer - more likely transmission. They can look at these outdoor social or other purpose group gatherings.

Proximity and duration of exposure.

However it's telling that TX or AZ specifically called out tubing recently. Outdoors activity but apparently some lakes become filled with people on inner tubes and they're close to each other.

Also, it's believed that one of the super spreading events in Italy and Spain was a big soccer match in Bergamo.

Now, did the infection spread in the stands of the match? Or maybe in all the get-togethers at bars and restaurants before and after the match?

A lot of the supporters of the Spanish team traveled to Bergamo and apparently took it back with them. However, they were from Valencia, not Madrid, which was the center of the biggest outbreak in Spain.

 

[REWahoo]

However it's telling that TX or AZ specifically called out tubing recently. Outdoors activity but apparently some lakes become filled with people on inner tubes and they're close to each other.

Tubing is done on rivers, not lakes here in TX. Floating down the Guadalupe river in Central TX is a popular summer pastime. It can get crowded as you can see.

 

[explanade]

That's what I thought but apparently in other places people just lounge on a tube in a lake, not moving very much.

Saw pictures of a couple dozen people on tubes all kind of lounging and next to each other.

 

[REWahoo]

That's what I thought but apparently in other places people just lounge on a tube in a lake, not moving very much.

Saw pictures of a couple dozen people on tubes all kind of lounging and next to each other.

The reason I pointed out river tubing, popular in TX, is that the possibility of exposure due to close contact is much higher than simply being near each other while floating on the water. Tubing outfitters have large parking lots, rent tubes and then pick up tubers miles downriver, transporting them back to their cars. This is usually done in an old school bus, packed together like sardines. Perfect opportunity to spread the virus.

 

[slingshot]

I think one issue with tubing in Az is the bus shuttle service that transports the tubing public. The Ozarks party looked like it was mainly private boaters. Another issue is the amount of alcohol consumed makes Az tubing more like a floating bar. Lowered inhibitions, lack of social distancing. For context-the total number of hospitalized cases in Maricopa County is still 2600 of 4.5 million, and just over one half the deaths from Covid have been care homes.

 

[explanade]

The reason I pointed out river tubing, popular in TX, is that the possibility of exposure due to close contact is much higher than simply being near each other while floating on the water. Tubing outfitters have large parking lots, rent tubes and then pick up tubers miles downriver, transporting them back to their cars. This is usually done in an old school bus, packed together like sardines. Perfect opportunity to spread the virus.

I think one issue with tubing in Az is the bus shuttle service that transports the tubing public. The Ozarks party looked like it was mainly private boaters. Another issue is the amount of alcohol consumed makes Az tubing more like a floating bar. Lowered inhibitions, lack of social distancing. For context-the total number of hospitalized cases in Maricopa County is still 2600 of 4.5 million, and just over one half the deaths from Covid have been care homes.

Ah that makes sense, especially the logistics of riding together back on buses.

Or for that matter if there's a lot of socializing in close quarters before and after the activity, like at restaurants.

 

[Buckeye]

Proximity and duration of exposure.

However it's telling that TX or AZ specifically called out tubing recently. Outdoors activity but apparently some lakes become filled with people on inner tubes and they're close to each other.

Also, it's believed that one of the super spreading events in Italy and Spain was a big soccer match in Bergamo.

Now, did the infection spread in the stands of the match? Or maybe in all the get-togethers at bars and restaurants before and after the match?

A lot of the supporters of the Spanish team traveled to Bergamo and apparently took it back with them. However, they were from Valencia, not Madrid, which was the center of the biggest outbreak in Spain.

I been tubing on the Salt River and my guess is the actual tube time is not the issue. It's probably groups riding in vehicles together to and from the location, groups talking and laughing and yelling prior to and after the actual tubing, and friends gathering for a few drinks after tubing..

 

[capjak]

Outdoors lower infection rate, yes. Protests did not result in a spike. That is hard to estimate.

1. Most states started reopening already so not sure an increase would be distinguishable

2. Many of the protests had a younger group of people. Younger people have a lower incidence of severe symtpoms and therefore may not get tested as frequently, as majority do not feel sick.....

I remain cautiously optimistic but...no real way to know the impact of 1,000s of people next to each other some with masks spreading the virus

 

[audreyh1]

Outdoors lower infection rate, yes. Protests did not result in a spike. That is hard to estimate.

1. Most states started reopening already so not sure an increase would be distinguishable

2. Many of the protests had a younger group of people. Younger people have a lower incidence of severe symtpoms and therefore may not get tested as frequently, as majority do not feel sick.....

I remain cautiously optimistic but...no real way to know the impact of 1,000s of people next to each other some with masks spreading the virus

Yes, but they have found distinct outbreaks associated with many other gatherings. Even some of the church services outdoors because of laying on hands and singing.

 

[donheff]

I think Maas is reaching too far. There seems to be a consensus developing around a spectrum of risks tied to the length of time of exposure and degree of exposure. Indoors groups without masks fall in the high risk end. Outdoors with masks very low risk. Outdoors without masks likely depends on how close you are to others and for how long. Individuals passing by each other probably don't generally lead to a long enough and strong enough exposure to case an infection -- but, no guarantee. Most of the beach scenes I have seen in the news actually look pretty spread out so spikes may not result.

Marches and protests likely vary in their impact depending on whether the participants are largely wearing masks or largely unmasked. Where most participants are masked the situation is sort of like herd immunity with most of the masked participants protected and many of the unmasked sheltered by the masked around them -but not everyone would escape unscathed. Some spread almost undoubtedly occurred, just not enough to document. Absence of evidence is not evidence of absence.

 

[bloom2708]

A friend made an excellent analogy - think of how far away you can smell a cigarette. That's not dissimilar to how someone's breath will spread out.

It freaks me out to be walking with a mask, and having mask-less joggers run by me huffing and puffing...and then walking through their germ cloud. It happens frequently during every walk. (I never thought I'd be such a germaphobe!)

I can't go for my usual walks anymore and have started to use the in-between alleys to stay away from people.

A few days ago I was out for a walk. I was on the sidewalk on one side of the street. A guy walking on the other side was smoking. It was breezy. I could smell the smoke from his cig for at least a 1/2 block. Indoor, outdoor, the virus is very powerful if you are in contact. I'm not sure what all factors in, but we'll continue to remain cautious.

 

[sengsational]

Celebrations yesterday

Who thinks the US we'll see a spike 5 to 7 days from now?