Yes, Actually, We Should Go Outside, Just Not Like A BUNCH OF ASSHOLES
If you didn't already see it in this morning's Tabs, you should go over to Vox and read this nifty summary of what experts say the USA should be doing to control the Rona and safely get the economy going again. It's very good! TL;DR version (if Vox is too long for you, rethink your reading habits): We could be doing this smart like a lot of other countries are, and it's still not too late to smarten up now, but it would require the USA to commit to a real plan and also spend money (so enjoy your second wave of COVID-19). Rather than summarize the whole thing, which would be Voxing Vox, which would be Axios we guess, let's look closely at one of those points. In addition to wearing masks everywhere, getting testing rates up (and testing smarter), doing serious contact tracing, and such, the article suggests there would be some real benefits to letting people go outside more, as long as we can manage to not be incredibly stupid about it. (We are Americans. Good luck to us.)
Here's the basic point: While limiting indoor public gatherings (especially in crowded settings) is still very much necessary to prevent transmission of the virus, the evidence seems to suggest that outdoor spaces like parks and beaches can be reopened, as long as people maintain social distance and wear masks while they're in those spaces.
Outdoor air is not magic, and it is possible to inhale droplets from another person's mouth outside. But the evidence seems to indicate that outdoor transmission is not, in practice, a huge problem. A detailed study of public outdoor spaces in Wuhan, China, found "undetectable or very low" levels of virus everywhere they looked. A study of more than 1,000 confirmed Covid-19 cases in other Chinese cities could only document one case of outdoor transmission.
Let's look at some science on all that, shall we?
Biology and epidemiology professor Erin Bromage explains, in an article you should probably bookmark so you can point at it and tell others to read it too, that the virus spreads when people are exposed to a sufficiently infectious dose of the virus, and it doesn't have to be a hell of a lot. While the exact exposure amount is still being determined, he offers this explanation to illustrate, based on doses already known for other coronaviruses:
Some experts estimate that as few as 1000 SARS-CoV2 infectious viral particles are all that will be needed [...] Infection could occur, through 1000 infectious viral particles you receive in one breath or from one eye-rub, or 100 viral particles inhaled with each breath over 10 breaths, or 10 viral particles with 100 breaths. Each of these situations can lead to an infection.
Bromage explains that coughs and sneezes expel lots of "respiratory droplets" at high speed, like 3,000 droplets for a cough and 30,000 for a sneeze. While large droplets fall quickly, teensy-tiny ones can travel across a room in seconds. Add a virus to the mix, and you have a very efficient infection-spreading mechanism:
If a person is infected, the droplets in a single cough or sneeze may contain as many as 200,000,000 (two hundred million) virus particles which can all be dispersed into the environment around them.
Even breathing releases respiratory droplets, too, as do speaking (oh, look a fresh Washington Post story on new research), shouting, and singing. Not surprisingly, the latter two release more particles. For infections to occur, you need to be exposed to enough viral particles cumulatively. So if an infectious person sneezes right at you, you've probably gotten a sufficient dose right there.
You don't need to be the direct recipient of a high-dose viral gift to get sick:
But even if that cough or sneeze was not directed at you, some infected droplets--the smallest of small--can hang in the air for a few minutes, filling every corner of a modest sized room with infectious viral particles. All you have to do is enter that room within a few minutes of the cough/sneeze and take a few breaths and you have potentially received enough virus to establish an infection.
And that's why everyone should be wearing masks — they don't do much to protect the wearer, but they're likely to significantly reduce the particles being expelled into the room. Infected people can spread the virus up to five days before they have any symptoms, so just saying "I feel fine" is a shitty reason to go without a mask.
The low amounts of virus expelled by normal breathing, about "20 viral particles per minute into the environment," means that you're fairly safe going shopping, even if an infected person wearing a mask breathed in the coffee aisle. But the stuff builds up in enclosed spaces, which is why reopening offices is a bad idea, and why even if shoppers aren't at risk, store workers can become infected (and this is all just from respiration, leaving aside viral particles on things or "fomites" in medical-talk). So It's all about viral exposure X time. And maybe add in airflow as another factor: An hourlong meal in a restaurant is a lot more dangerous than that same hour sitting outside. (But hey, maybe you could also just fucking wait.)
Bromage presents several scenarios in which viral outbreaks have occurred, like a restaurant meal where one asymptomatic person dining with nine friends infected half the people at their own table, as well as multiple folks at a table "downwind" (in the airflow from an air conditioner). Or a community choir where, even though everyone was careful not to shake hands and to keep socially distanced, one asymptomatic person infected virtually everyone in the choir. Singing involves deep breathing, and the two and a half hour practice meant enough viral particles were in the air that the prolonged exposure defeated the social distancing. "Over a period of 4 days, 45 of the 60 choir members developed symptoms, 2 died. The youngest infected was 31, but they averaged 67 years old."
Bromage reviews other outbreaks, including a workplace where most people on one side of an office got sick (airflow again), and a case where one infected, asymptomatic man shared a takeout meal with family members, then shortly afterwards, attended a funeral and a birthday party. The man became sick and eventually died, and those he contacted went on to infect others, too. In total, 16 people were infected, of whom three died.
There are some common factors here:
All these infection events were indoors, with people closely-spaced, with lots of talking, singing, or yelling. The main sources for infection are home, workplace, public transport, social gatherings, and restaurants. This accounts for 90% of all transmission events. In contrast, outbreaks spread from shopping appear to be responsible for a small percentage of traced infections. (Ref)
Importantly, of the countries performing contact tracing properly, only a single outbreak has been reported from an outdoor environment (less than 0.3% of traced infections). (ref)
And so, Bromage concludes,
as the work closures are loosened, and we start to venture out more, possibly even resuming in-office activities, you need to look at your environment and make judgments. How many people are here, how much airflow is there around me, and how long will I be in this environment. If you are in an open floorplan office, you really need to critically assess the risk (volume, people, and airflow). If you are in a job that requires face-to-face talking or even worse, yelling, you need to assess the risk.
So don't freak out too much about joggers or cyclists not wearing masks, unless they're jogging right in your face for several minutes. As Vox notes, "It's better for people to follow social distancing guidelines rather than flout them, but if they do break the rules or skirt the edges, it's likely safer to do it outside rather than inside." But maybe don't go to a demonstration where unmasked lunatics are yelling in each other's faces, even if it's outdoors. And sure, open parks, but nah, let's keep the playground equipment fenced off, because this virus definitely lives on surfaces. Sorry, Idaho anti-vaxxer jerkwads.
Now if we could just get people to understand that not wearing a mask doesn't make you brave; it makes you a potential super-spreader.
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Doktor Zoom's real name is Marty Kelley, and he lives in the wilds of Boise, Idaho. He is not a medical doctor, but does have a real PhD in Rhetoric. You should definitely donate some money to this little mommyblog where he has finally found acceptance and cat pictures. He is on maternity leave until 2033. Here is his Twitter, also. His quest to avoid prolixity is not going so great.