Outdoor transmission - Printable Version
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Outdoor transmission - akiddoc - 05-02-2020
I keep returning to this topic. Outdoor transmission of respiratory viruses has always been thought to be less common. If we truly practice what the science teaches, we will stop worrying so much about outdoor activities.
https://www.vox.com/2020/4/30/21232696/reopen-parks-coronavirus-covid-19
https://www.sfgate.com/science/article/China-study-suggests-outdoor-transmission-of-15229649.php
Outdoor transmission is not zero. But we aren't going to go to zero. There was documented outdoor transmission with SARS in 2002, which is probably why there was some worry. Balancing out risk and the reality of resuming normal activities, I would rank most outdoor activities as low risk.
RE: Outdoor transmission - dabigv13 - 05-02-2020
I think opening outdoor spaces with social distancing or masks if social distancing can't be easily mantained, is a good idea. A problem near metro areas is when a lot of people who can't do anything else all go to one of the few open parks or trails, then you can get some actual crowded situations that I think are problematic.
RE: Outdoor transmission - OutsiderFan - 05-03-2020
So we can conclude freakout over scenes of crowded beaches has been more about “optics” than actual reason for concern? And even that those people were actually being smart without knowing it?
As for baseball and football, we sit much closer to people in stadiums than we do at the beach, and we sit in the same place for 3 hrs. But even these realities are not nearly as concerning as the packed entrances and concession areas in most large stadiums, and public transportation particularly for MLB and NFL.
The game I went to at Stanford Stadium last year:
-Packed CalTrain from Mtn View to Stanford for 15 mins
-Security entrance queue at Stadium
-Close contact with dozens of people around stadium to stairs
-Not much contact going up stairs or at my upper deck seats during game
-Concessions on top of stadium in open air
-Packed bathrooms
-Leave Stadium early 4th quarter with no close contacts
-Wait in crowded line for maybe 45 mins at platform
-Packed CalTrain from Stanford to Mtn View
So I would say the three most vulnerable environments were:
1. CalTrain
2. Bathrooms at stadium (even porta potty would be spread vector)
3. Entering Stadium (or leaving if game was close at end)
So even if just being outside reduces transmission to acceptable levels, even in a crowded stadium packed to the gills, there are other spread vectors that probably aren’t acceptable to have fans. And in my case, the concessions were outside in open. Would not have been case if I was at the mezzanine level. As you all know, thousands of fans are congregated in the middle concession level under the second deck to take refuge from the heat during day games. This was the case for the Oregon game last year.
RE: Outdoor transmission - Farm93 - 05-03-2020
I fear some sport and music loving fans hear that China had almost no outdoor transmissions and will then jump to a set of questionable conclusions.
Wuhan in January is not exactly an outdoor paradise. The weather in December and January is not great. Chinese urban citizens are not exactly known for their love of outdoor cafes or winter spectator sports. Oh, and throughout Asia it was understood that there was a dangerous virus lurking in many cities.
So while Asia had few outdoor transmissions in that sample, I think it would be very dangerous to conclude their experience would mean it will be safe to crowd into an outdoor music festival, socialize in a multi-hour tailgate, or crowd into a football stadium for 3 hours.
I would rather be at a big outdoor stadium than a crowded meat processing plant, but I don't think the East Asian winter outdoor experience is really transferable to USA summer activities.
FWIW - I thought the running theory was that Spain and Italy had their initial outbreaks because of a soccer match in Northern Italy. I am not sure if that tracing was ever investigated more carefully, but that type of Western European sports experience would seem to be far more relevant for USA sports fans.
RE: Outdoor transmission - Mick - 05-03-2020
(05-03-2020, 06:32 AM)Farm93 Wrote: FWIW - I thought the running theory was that Spain and Italy had their initial outbreaks because of a soccer match in Northern Italy. I am not sure if that tracing was ever investigated more carefully, but that type of Western European sports experience would seem to be far more relevant for USA sports fans.
https://www.wsj.com/articles/the-soccer-match-that-kicked-off-italys-coronavirus-disaster-11585752012
https://time.com/5809848/game-zero-soccer-game-italy/
https://slate.com/news-and-politics/2020/03/bergamo-italy-champions-league-soccer-match-atalanta-valencia-biological-bomb-coronavirus.html
https://time.com/5809848/game-zero-soccer-game-italy/
RE: Outdoor transmission - Snorlax94 - 05-03-2020
Yeah I could see sports events and political rallies being an exception to the general rule of outdoors being low risk because sporting events have the combination of:
- extreme concentration of people (close enough to high-five someone two rows behind you)
- massive raw numbers (tens of thousands)
- prolonged exposure (2+ hour events)
- people screaming/chanting/expectorating, at their maximum volume, for hours
- additionally, because stadiums are partially enclosed, ventilation is worse
My guess is that beaches, even if there were thousands of people, would be reasonably safe, as long as people were more than 20’ apart.
My largest concerns about the beach is that people could stay there a long time (so if the breeze always blew in roughly the same direction, one infected person could keep spraying the same people downstream), and that it could facilitate multiple households mixing a little too regularly.
But overall, my guess is that it’s safe. Plus, if you feel sick, you might go to a friend’s house, but it’s less likely you’d trek out to a beach.
I am all for transitioning as many activities as possible outdoors, as long as the crowds are not large, the sick stay home, and things are spread out.
RE: Outdoor transmission - 2006alum - 05-03-2020
Maybe I'm missing something, but I thought the whole six-foot distance thing was primarily for outdoor activity (along with grocery stores and other large indoor spaces providing essential services), and that it was premised on the idea that six feet of distance + being outdoors or transiently indoors = minimal likely transmission?
After all, if I'm stuck in a small 8'x8' office with a COVID-19 shedder coughing for 12 hours a day, a six foot distance isn't going to stop transmission, right? That's presumably why nursing homes are vectors even where the inmates ahem residents are more than six feet apart? And same for hospitals?
And by the same token, I have never seen any claims that large crowded groups of people in close proximity for hours on end will not transmit the virus just because they're outside.
So I guess in my mind the major challenge we face is in dealing with the fact that many long-duration activities (like office work) have to take place in indoors, while many group activities that take place outdoors are not ones that can readily accommodate the six feet of distance requirement?
RE: Outdoor transmission - fullmetal - 05-03-2020
I think 2006alum has it. The six feet rule doesn't seem to protect you indoors (that case study of restaurant infections from table to table). Even outdoors, if you're exactly six feet away from a contagious person, I would expect sustained proximity to increase your odds of infection substantially...
RE: Outdoor transmission - burger - 05-03-2020
(05-03-2020, 07:09 PM)fullmetal Wrote: I think 2006alum has it. The six feet rule doesn't seem to protect you indoors (that case study of restaurant infections from table to table). Even outdoors, if you're exactly six feet away from a contagious person, I would expect sustained proximity to increase your odds of infection substantially...
I agree with both you and 2006alum. That's why I am extremely worried about plans to open up schools, offices, etc. while acting like 6' of separation is a magic force field that prevents virus transmission. My current feeling (which admittedly could change with new evidence on transmission dynamics) is that there is no safe way to reopen offices, schools, etc without a vaccine, cure, or very extensive testing.
RE: Outdoor transmission - dabigv13 - 05-03-2020
I think if you make everybody in the office or school wear masks, and have good ventilation systems, possibly combined with UVC light decontamination, you could maybe have a reasonably safe setup, combined with social distancing. Hard to envision how most school systems would have the space or budget to really make it work though. Maybe some businesses.
RE: Outdoor transmission - akiddoc - 05-03-2020
https://www.sciencedirect.com/science/article/pii/0160412082900435
RE: Outdoor transmission - Snorlax94 - 05-03-2020
(05-03-2020, 07:34 PM)dabigv13 Wrote: I think if you make everybody in the office or school wear masks, and have good ventilation systems, possibly combined with UVC light decontamination, you could maybe have a reasonably safe setup, combined with social distancing. Hard to envision how most school systems would have the space or budget to really make it work though. Maybe some businesses.I worry this would not be enough and couldn’t be implemented widely, quickly. It’s hard to imagine most everyday businesses being able to implement a system with effective uvc air decontamination anytime soon. Maybe Apple or Google could, but not a meat packing plant, a Target store, or a mom and pop record store
I agree the 6’ rule is a lie. It has some usefulness for large droplets but indoors it’s like the old nuclear war drop and cover instruction “if a nuclear bomb goes off nearby, drop under a nearby desk and use a newspaper, if available, for cover.”
I think what will happen is:
1) many essential industries, like meat packing, are cruelly being forced through herd immunity quickly
2) Companies that can should telecommute
3) everyone else needs to reconsider their workflows. I can’t imagine a way to make a call center or telesales center work in a large office. They need to find a way to get people to work from home or something. if you have 200 call center workers on one floor, it is a recipe for disaster no matter how you rearrange the desks or whether you can clean the air nightly. And often, the more packed the employees, the smaller the capital budgets for quickly installing a cutting edge hvac system.
For many tech campuses I’ve seen, for example, there are already existing tables outdoors and wifi throughout the campus for meetings, assuming they can’t telecommute. I won’t eat at a restaurant indoors no matter what the table configuration is or whether they have a uv contraption in the corner, but I might eat outside.
My old CIV lecturer would let us discuss Aristotle, the Tao Te Ching, Shakespeare, outside on the grass. I admit it can be distracting, but it’s better than having young kids look at Chromebooks all day. Why can’t we try that in CA, especially because the weather is so good.
RE: Outdoor transmission - fullmetal - 05-03-2020
Good indoor ventilation no longer means what it used to mean. Prior to covid, I think good ventilation would have meant active circulation of air that mixed fresh, filtered air with recircled air. Now, I think good ventilation means removing exhaled air from the vicinity of people as soon as possible. When outdoors, the wind tends to do most of the work. Indoors, active circulation means exhalation from one person has a higher likelihood of contacting more people...!
Cube farms or open office plans = nope. Individual offices = nice.
If your HVAC system was designed to remove air from the ground level while adding air from above, you could definitely make the argument that the exhalations would likely flow to the floor and be removed from immediate proximity to others, but barring that, active indoor circulation might be counterproductive.
Short guess: most indoor gatherings are still not great under any reasonable distance.
RE: Outdoor transmission - OutsiderFan - 05-04-2020
There is debate here in West Hartford about closing a downtown street that is setup for 45 degree parking, and using it as expanded space for dining tables because there are so many restaurants on it.
This could probably be done at places like Murphy Street in Sunnyvale and maybe even California Ave in Mountain View.
Drive-in theaters are about to be all the rage again.
RE: Outdoor transmission - stupac2 - 05-04-2020
(05-04-2020, 03:47 AM)OutsiderFan Wrote: There is debate here in West Hartford about closing a downtown street that is setup for 45 degree parking, and using it as expanded space for dining tables because there are so many restaurants on it.
This could probably be done at places like Murphy Street in Sunnyvale and maybe even California Ave in Mountain View.
Drive-in theaters are about to be all the rage again.
There was some discussion about drive-ins on the bay area subreddit and the conclusion was that there are still too many shared points of contact (concessions and bathrooms, mainly). You could probably manage concessions with some kind of app sales and carhops, but bathrooms would be tricky.
RE: Outdoor transmission - 2006alum - 05-04-2020
For drive-ins, why couldn't they have the equivalent of the attendants in clubs who manage in-flow and out-flow of busy bathrooms? You could just station someone at each bathroom to ensure it's one-in, one-out. And especially if you required attendants to wear a mask while using the facilities, it seems like there'd be very limited possibility of transference.
And I hope SF is also thinking about blocking off streets for restaurants to expand out into for outdoor seating. I think that's a great idea, and with some additional outdoor heaters, could allow restaurants to operate at a sustainable volume of business while also observing social distancing.
RE: Outdoor transmission - BostonCard - 05-04-2020
Six feet is not a lie, it is a guideline. Of course it does not mean that is some sort of "cone of infection" within which COVID-19 will be transmitted and outside of which it will not. Transmission is probabilistic, with the probability of transmission inversely proportional to distance between them (likely as a factor of the square of the distance), and directly proportional to the amount of viral shedding by the infected patient and the length of time of the interaction. It is also related to the setting, air circulation, and (likely) temperature and humidity, and mask wearing.
As always, one can only reduce risk, you can't eliminate it entirely. Shorter interactions with fewer people from further away will reduce risk. There is no magic about 6 feet, but there is a good chance that the risk is falling rapidly around the 6 feet mark.
BC