Category: COVID through 2022

The point of this post is to estimate what fraction of the Fairfax County adult population is likely to be walking around in an infectious state.  That is, for every 100 adults you encounter outside the home, what is the likelihood that you encounter at least one person who is capable of infecting you with COVID-19.

The upshot is that, for Fairfax County, we are approaching the point where 1% of the adult population, at any one time, is walking around in an infectious state.  Right now, my best estimate is 0.8%, but give it another week or two, and at the current rate of growth, that will be 1%.

This is a pretty strong argument for continuing the ban on large public gatherings, particularly church services where singing will occur.  Singing generates as much aerosol as coughing, and all it will take is one infected person who is a “superemitter” to generate a significant cluster of new cases.  See Post #679 for a summary of this issue.

This is an update to Post #624.  And when I compare the current and prior estimates, in the roughly four weeks since I did that, the number of disease carriers circulating in the population has doubled.

The methods are laid out in Post #624.  Take the count of newly discovered cases for the past four days, inflate that to account for case growth over time, and add in a factor for likely cases that will never have an official diagnosis of COVID-19.  And that should give you a reasonable guess for the fraction of the adult population that is current capable of spreading the disease, but doesn’t yet know it.

This does not account for individuals who never have symptoms, and yet may spread the disease for some extended period of time.  I think the jury’s still out on that one.  The pre-symptomatic population very definitely sheds virus and spreads infection.  It’s not clear that the people who never have any symptoms do the same.

There are only two things I would change, from my prior analysis.  Those are the labeling of my “best case” and “worst case” scenarios.  These were estimates of the number of persons who had COVID-19 but were never counted as officially diagnosed with it.

In the month since I did that least estimate, there have been several studies of the fraction of various populations with antibodies to COVID-19.  Based on those, it’s pretty clear that in the typical case, the cumulative number of person who have had COVID-19 is, in fact, several times larger than the cumulative number of persons who were formally diagnosed with it.  My “best case” scenario now appears to be far too optimistic, and I’d say that my “worst case” scenario is about the middle of the pack, in terms of the results of these studies.  I have remove and relabeled the estimates accordingly.

Source:  Religion News Service.

Just thought I would bring this to your attention.  Not only have the Germans figured out that singing in church is dangerous (and so is banned for now), so have the Koreans.  Or, at least, some of them.  This, from the New York Times:

"Worshipers at one of Seoul’s largest Catholic churches must refrain from singing hymns or saying “amen” for fear of spreading saliva. "

Interestingly, both countries had their own version of our superspreader event, a Mount Vernon, Washington choir practice were 45 of 60 in attendance fell ill with COVID-19.  Germany had roughly three-quarters of a large church choir fall ill, from which they took a clear lesson.

And in Korea, one large outbreak was traced back to a single sick parishioner at one tightly-run cult-like church.  She infected nearly 40 other church attendees, who went on to infect hundreds, plausibly thousands, total, before that particular outbreak was stopped.  Separately, and despite this, Korea had to take legal action against several Protestant churches for defying their ban on public gatherings.

Turns out, pretty much every country, and almost every state, has had its own version of a church-based super-spreader event, or at least large clusters of cases related to church attendance.

Here’s a similar experience in France, where, once again, apparently one ill worshiper at a large Gospel church gathering set off a chain of infections that, ultimately, led to 2500 people being infected with coronavirus.  This one cluster was the principal reason that Germany closed its border with France.

Here’s a church in California that managed to start a 70-case cluster, despite the church being shut down.  Seems that parishioners got the bright idea of meeting in large, crowded groups in each others homes.  Here’s a different writeup of the same event.  As of a month ago, one-third of all cases in Sacremento County, CA, were tied to church attendance.

At least one Canadian province has gotten the message, and has banned singing in church.  In this case, in live-streamed church gatherings that are already limited to 15 or fewer people.  And, almost predictably, the churches plan to sue over it.  The Alberta, CA ordinance was modeled after a similar ordinance in Mendocino County, CA.

Kansas reports three separate clusters of cases related to church attendance.  This was back before Easter.  And, predictably enough, the Kansas legislature then exempted churches from bans on public gathering.

Here’s a cluster of cases from a Kentucky church revival meeting.  Here’s a writeup of that church’s response.

Here’s an Arkansas church that continues to hold services despite the fact that a nearby church was itself the center of a large cluster of cases.  Which reminds me of my “Darwin Test”, Post #633.

California is, as usual, leading with way to a solution — with drive-in church service.  Apparently many states are following suit.  Hence the picture and article reference at the top of the page.  Seriously, just Google images for “drive-in church” and you’ll see this is now all the rage.

But the question remains:  Even if some people can be smart enough to modify their behavior — no singing, say; or live-streamed services; or drive-in church — will there be enough dummies out there to make church service a continues source of clusters of infections?   Even though we now have many, many examples, internationally and across the US states, of this sort of event.

I guess, as states re-open, we’re going to find out, one way or the other.

My daughter asked about drive-in theaters the other day.  I’m old enough to remember two that used to run in this area. Or at least think I do.  There was a drive-on on, of all places, Route 1 near Mount Vernon.  That was still in existence, as I recall it, about 35 years ago.  And seem to recall one on Route 28, just south of Manassas.  That is, of course, long gone.  In all of Virginia, there are only a handful left, and most of those appear to be run as not-for-profit nostalgia venues, rather than as commercial enterprises

Source:  The Atlantic.

1:  The Germans have had their act together on this from Day 1.  Please see Teutonic Two-Tier Testing, among other posts.

2:  Aerosol spread is the bugaboo that the US CDC cannot deal with.  (See front page here if you don’t understand what aerosol (airborne) spread of COVID-19 is.)  I have been noting the idea of aerosol transmission of COVID-19 for weeks now.  It’s obvious that it’s a risk, it’s not clear how frequently it occurs.  It’s clear that the CDC will not publicly acknowledge it.  Even if it’s impossible to explain the spread of COVID-19 without it.

3:  I have repeatedly noted the super-spreader event that occurred with the Mount Vernon, Washington choir, which could not possibly have been anything but aerosol spread.

4:  Singing produces as much aerosol as coughing.

That’s all stuff that I’ve been referencing for weeks here.

5:  Now go read this:  Germany will allow religious services, but they ban singing.

Please note that:

5.1:  They had their own choir event:  ” … and in Berlin, where 59 out of 78 singers from the choir of Berlin’s Protestant cathedral went down with the virus – have offered plenty of anecdotal evidence that singing in choirs has contributed to the spread of coronavirus in some communities.”

But, unlike the USA, their government epidemiologists paid attention.

5.2: ” … despite repeated warnings by leading epidemiologists that singing is as dangerous as coughing for spreading the virus.”

Why?  Because their Federal government is smart.  Angela Merkel is not only the daughter of a Lutheran pastor, she’s a bona-fide scientist.  They are looking at the same research that I have been looking at, and they have come to the same conclusion that I have.

So the Germans can start from a basis of facts, and then discuss the policy merits of allowing singing in large (cathedral) spaces or not.

Meanwhile, our Federal government remains clueless.  And if we rely on that Federal government for information, we end up just as clueless as our leaders.

I’m ashamed for the USA.  I’m ashamed that the Brits are going to beat us to a vaccine, by half a year or more.  I’m ashamed that the Germans have figured out that choral singing is a risk.  While here in the USA, we’re doing our damnedest to ignore basic science.

Stupidity gets punished, in the long run.  I suspect we’ll be paying for this for the next generation.

Source:  Wikipedia.

Well worth the read if you need a bit of good news.  From the New York Times.

Jenner Institute, Oxford, England, has a vaccine well along in the pipeline.  Known to be safe.  Effective in monkeys, which is as close as you can get to a test on humans, short of a test on humans.

Large-scale human trial (6000 persons) scheduled for next month.  The deal is, because this is deadly, they can’t do what they did to the monkeys, and just expose a bunch of people to a deadly dose of the virus.  Instead, they have to vaccinate a bunch of people, placebo-vaccinate a second group, and then look at the naturally-occurring infection rates in the two groups.  Hence, testing it on 6000 persons.

They should know for sure whether it works or not, on humans, June/July of this year.

Today’s news is that they’ve lined up a manufacturer.

They skipped Phase I trials, which is my bugaboo about US vaccine research.  Phase I trials costs lives, this context, because delay is costly.  This approach had already been shown to be safe, and so the British government gave them approval to proceed.  Makes me wonder what it must be like to have a national government that can act rationally.

 

Source:  clipart-library.com

Today, this story popped up.  Vilnius is going to turn its public spaces into open-air restaurants.

As described in Post #671, I think that has merit.  Based on what scant analysis exists, outdoor spaces in general appear safer than indoor.  A plausible reason for that is limiting potential for aerosol transmission of disease.  So, to the extent that we have any science to suggest what to open up first, this idea of using the public open space for benefit of the local restaurant industry makes a lot of sense.

The Lithuanians are no softies on these public health issues.   They just appear to be a heck of a lot smarter than we are.  They made face masks mandatory in public spaces earlier this month, and they enforced that with fines.  Now they’ve relaxed that, but only outside of heavily populated areas.  They banned inter-city travel at Easter.  And now they are in the process of relaxing restrictions.

It’s almost as if they think about what they are doing.  Maybe we have a few things to learn from Lithuania.  Particularly when, as of now, they have less than 10% the death rate, per capita, that we do, from COVID-19.

Given the choice, I’d shop a farmers’ market rather than a grocery store.  And I’d eat in an outdoor cafe before I’d eat in an indoor restaurant.

If we’re going to re-open businesses, we ought to do it as intelligently as possible.  And my reading of the data is that it’s a lot safer to do your business outside rather than inside.

Above:  Our clear downward trajectory, justifying removal of restrictions.  (Yes, that’s sarcasm.  But that’s the actual data.Source:  Calculated from Johns Hopkins coronavirus database., accessed 4/29/2020.)

I’ll start by repeating what I said 20 days ago, in Post #616, 4/9/2020.  At that time, I predicted that eventually, some people would start saying this:

“Our containment strategies worked, and we avoided mass deaths. And so the lack of mass deaths is evidence that our containment strategies were not needed.”

Substitute “are” for “were”, above, and you now know everything there is to know about the logic behind re-opening the economy.  If you believe that the thinking behind this movement to re-open state economies goes one inch deeper than that, or draws from some sound empirical basis, you would be mistaken.

Maybe fortune will favor those who open early.  Maybe not.  Maybe the cost of additional deaths is outweighed by the economic gains.  Maybe not.   Maybe, ultimately, economic gains will be negative, if this slows down the ultimate recovery from this pandemic. Or, maybe there will be no uptick in infections and deaths.  Nobody knows.  It’s all a roll of the dice.

No matter how you slice it, this is exactly the sort of situation where preparing for failure matters.  Failure is always an option.  Everybody will celebrate if this is a success.  But is anybody preparing in the states where this fails? Continue reading Post #673: Reopening Georgia and elsewhere, Post #2

Source:  None.  Good luck finding this.  Either the Feds finally got smart, and pulled the drug before the study results were released, or your neighbors have out-panic-shopped you once again.  Picture source:  Amazon.  Ah, yep, looks like the Feds may have learned nothing, and your neighbors beat you to it.

You want a little ray of sunshine:  Read this.  Just by chance, the structure of one common antacid interrupts replication of the COVID-19 virus.

This has all the elements of what I termed “scientific folk medicine”.  It was based on an observation in China, that the peasants seemed to be surviving at a higher rate that the elites.  That, in turn, appeared to be due to the peasantry being unable to afford the top-shelf antacids, and having to make do with the cheap stuff.  Next, a computer study came up with this, separately, as a good candidate to stop viral replication in this case.  No in-vitro studies, but surely those are in the pipeline.  And now we’ve had a couple of docs do their own “case studies” and convince themselves that it appears to work.  (“Penicillin-like” response, was the phrase, meaning, clearly the result of the drug, and not just chance.)

It’s currently undergoing a more-or-less proper clinical trial.

Lot of smart people, spending a lot of time, figuring this out.  That ups the odds that somebody will find something.  We just have to keep you-know-who from touting this one.

A personal note on the hoarding thing:  I’ve got acid reflux.  For years, I used ranitidine to keep that  in check.  Turns out, that causes cancer, so they pulled that off the shelves.  Great.  I switched to famotidine, which seems to work OK, but not as well as ranitidine, for me.  Now the panicky mobs have cleared that off the shelves.  I guess I’ll go back to sucking on Tums.

Source: COMMENTARY: COVID-19 transmission messages should hinge on science. March 16, 2020, Lisa Brosseau, ScD, author, on line at the University of Minnesota Center for Infectious Disease Research and Policy.  Used without permission here, under a claim of fair use.

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Guarding against aerosol spread is the only rational approach

I first stumbled across the likelihood of aerosol (airborne) spread of COVID-19 about a month ago (Post #585).   That is, the fact that COVID-19 can probably be transmitted by tiny (under 5 micron) particles that float on the air and can, in theory, travel significant distances.  In large part, that’s why I remain fixated on making masks capable of filtering aerosols (e.g., Post #648), until such time as ordinary citizens are allowed to buy commercially-made N95 respirators.

At this point, the likelihood of aerosol transmission seem so be working its way into mainstream discussions.  This has important implications for prevention actions that we need to take, particularly as more states open up larger segments of retail commerce and other businesses.

The US CDC still does not overtly acknowledge that aerosol (airborne) transmission is a likely route of infection for COVID-19.  This, despite the fact that at least one expert summary prepared for the government concluded just that, issued a few days prior to the change in CDC guidance to suggest that everybody wear masks when in public.  (Yo can see the original National Academies of Sciences summary letter at this URL.)

You don’t have to cough or sneeze to generate aerosols.  Talking generates a large number of such aerosol particles.  Not quite as much as coughing, but close.  Talking loudly generates more than talking softly, and singing generate aerosols at the same rate that coughing does (likely the ultimate cause of the Mount Vernon, Washington choir event).  Finally, some individuals are superemitters, generating vastly more aerosols than others.  All of this can be found in this very readable article in Nature.

It’s not as if aerosol transmission of disease is a radically new idea.  Many disease are known or thought to spread via aerosols, including tuberculosis, measles, and chickenpox.  In fact, those critical N95 respirators?  I believe that standard was literally established for dealing with tuberculosis (and, later, SARS 2003).  NIOSH and CDC literally mandated N95 respirators as a way to cut down on transmission of tuberculosis within the hospital. Expert opinion at this point is that COVID-19 is not as infectious, in this manner, as either measles or TB (op cit).

By contrast, the CDC has focused on droplet transmission of COVID-19.  This is transmission of disease by droplets (over 5 microns in size).  These largely drop out of the air within six feet of the person emitting them.  Droplet transmission is the basis of the 6-foot “social distancing” rule. 

Likely, the CDC’s position will not change because they don’t have evidence of adequate scientific quality to allow them to make that conclusion with certainty.  But here’s the problem:  Best case, it’ll take a couple of years of investigation before they can be sure that this was, in fact, spread in part by aerosol (airborne) transmission.  And so, as with so much of our federal public health infrastructure, they are hidebound by rigid adherence to rules that are completely out-of-place in the context of the current pandemic.

But if and where aerosol transmission is important, social distancing is not enough.  So I’d say it’s fairly important (and high time) that scientists get a handle on the situations where aerosol spread is more likely (outside of hospitals) and start offering some advice on how best to avoid it.

It’s all about the dose:  Hospitals are at one end of the spectrum of exposure to viral aerosols.  They end up with a high concentration of aerosol particles, due to a) high virus shedding rate by very ill people, b) small, confined spaces in hospital rooms, and c) staff who must spend considerable lengths of time in those spaces.  All three combine to raise the risk that hospital personnel will inhale a dose of aerosolized virus large enough to cause them to become infected.  Hence, a requirement for use of N95 respirators and use of negative-pressure rooms to restrict spread of aerosolized virus.

If that’s one end of exposure, where you get the highest dose of aerosolized virus, then I’d say that sparsely populated outdoor areas are at the other. And that is, in fact, what experts appear to say.  Like so:

"If you generate an aerosol of the virus with no circulation in a room, it's conceivable that if you walk through later, you could inhale the virus," Fineberg said. "But if you're outside, the breeze will likely disperse it."  (op cit).

And that’s not just a bunch of hot air.  Analysis of the Chinese experience showed that outdoor transmission of COVID-19 was rare, among all instances in which the transmission could be traced.  Quite rare.  Just one case, among more than 7,000 cases studied was attributed to transmission outdoors.  (That was from two guys have a conversation outside). That’s reported in this newspaper article.

In that Chinese study, for “clusters” of cases (where there were several cases that could be shown to be related), the prevalence of transmission site (may add to more than 100%, as multiple routes may be involved) was:

• Within the home (79.9%)
• Public transport (34%)
• Followed by:  restaurants and cafeterias, entertainment (gyms, teahouses, barbershops), shopping (malls and markets) and miscellaneous.

  “This study shows that the individual indoor environments in which we live and work are the most common venues in which the virus of the once-in-a-century-pandemic is transmitted among us,”  ( same newspaper article.).

Note that the rates above are raw prevalence data, and don’t adjust for how frequently individuals were exposed to those environments.  I.e., gyms might be particular hotspots for spread of disease among those who use them, but they would show up low on the list if relatively few people used gyms.

Here’s a readable summary of evidence of aerosol transmission of COVID-19, mostly in China and Japan.  They cite a 20-times-higher transmission rate indoors as compared to outdoors, and cite several examples from restaurants and other indoor settings where aerosol spread was the only plausible mechanism.  All of this is for the obvious reason that, for a given density of persons, aerosols will disperse far faster outdoors than indoors.

Finally, within the category of “indoors”, research spotlights high-traffic areas where moisture is present.  They point to bathrooms and changing rooms (pay attention if  you are going back to your gym!).  But if I had to identify a high-density high-moisture area, the first place I’d point to is a meat-packing plant.  So, once again, I’m betting that (eventually) they’ll figure out that the spate of superspreader-type events in meat plants is not a concidence, but is part-and-parcel of the work environment.   Let’s get our meat packers some N95 masks.

That research above also seconds the China findings regarding public transportation.  Apparently, in Boston, the prevalence of viral particles on subway turnstyles correlates well with the prevalence of COVID-19 in the surrounding neighborhoods.

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Farmer’s markets as a model of safe commerce.

What get me thinking about this was the proposed re-starting of the Vienna farmers’ market later this year.  Someone casually asked me if I thought that was safe, and my immediate response was, that’s safer than shopping in a grocery store.  And it was exactly because it was out-of-doors.  As long as it doesn’t get too crowded, I’d far rather shop at a farmers’ market than indoors at the grocer.

In fact, I had already said (Post #600):

“If aerosol transmission of this disease actually does occur frequently, and vendors won’t wear masks, then an open-air market on a windy day is probably your safest bet for shopping, and long as the density of individuals is kept low.”

Now that research is starting to come out, I’m standing by that.  I don’t think the Town should hesitate even one bit about this.  Because the research now strongly suggests that if this is an alternative to shopping indoors, it’s probably safer than the alternative.

But that got me thinking.  Are there other pieces of commerce that can be done this way?

The first obvious candidate is outdoor dining.  Assuming this research is right, the obvious implication here is that the Commonwealth should have more relaxed rules for resumption of outdoor dining than indoor.

The second obvious candidate is organized exercise classes.  To the extent possible, if the Commonwealth is going to allow (e.g.) gyms, yoga studios, and similar to re-open, they again should have more relaxed rules for appropriately-spaced outdoor exercise.

Beyond that, it’s hard to think of major classes of commerce that could be done this way.

And, separately, I’d say that no commercial construction built in the last half-century was designed with any significant natural ventilation in mind.  Because, more-or-less, a strong breeze blowing through an area puts your ventilation on a par with being outdoors.  But I would bet that few-to-none of the commercial establishments in Vienna have enough free ventilation area (screened and openable windows and doors) to make that happen.

Barring that, the best thing you can do is wear the best mask you can, at all times where you share indoor spaces with others, outside of the home.  Near as I can tell, a lot of the remaining transmission is likely aerosol transmission by pre- or non-symptomatic individuals.  Any time you are sharing an indoor space, you are somewhat at risk for that mode of transmission.

The CDC appears dead-set against explicitly mentioning aerosol transmission.  And so, all of its rules are geared to something that simply does not happen now:  coughing and sneezing by symptomatic individuals.  In short, their public hygiene guidance is … well, useful, but obsolete.  It addressed a situation that might have existed two months ago, but no longer exists.  (Not-being-sick-in-public is now rigidly socially enforced).

So it’s incumbent on you to do what’s right, even if the CDC won’t tell you.  This becomes even more important as larger segments of retail commerce are again opened up.  My advice:

• Do what the CDC says, and:
• Wear the best mask you own, particularly if it will filter aerosol particles.
• Do your business out-of-doors when you can.
• Don’t talk unless you need to, and then, talk softly.

If this now is all about indoor aerosol transmission by asymptomatic individuals, then the rules need to change.  Please try to get ahead of the curve.

I got a few surprises yesterday as I went out to do my weekly grocery run.

First, I decided to give Whole Foods a try.  But failed.  The first surprise is that, around 1 PM yesterday, the parking lot at Whole Foods was filled.  I mean, to the point where, sure, I could have found a spot.  But I would have had to drive around to find one.

Obviously, I did the smart thing and went elsewhere.  Given how narrow the aisles are in that store, and how tight the clearances are in general, I’m surprised that Whole Foods isn’t limiting the number of patrons that they allow in the door.  But as of yesterday, at least from the outside, it looked like any normal busy Saturday morning.  The number of shoppers in the store was only limited by the number of parking places in the lot.

I went to Fresh Market.  And, as illustrated above, there was no such crowding at Fresh Market.  To me, that store has the same narrow, tight-tolerances feel as Whole Foods.  But they take this so seriously, and the shoppers take it so seriously, that there’s never an issue of feeling like I’m taking an unnecessary risk.

That said, either they’ve rescinded their no-mask-no-service policy, or they don’t enforce it.  A couple of clueless twenty-somthings were shopping together, having a nice time, no masks.  While all the codgers like me were masked and totally on-task the entire time.  We clearly live in different worlds.

There were a handful of items that I could not get at Fresh Fields, including items that my wife wanted for her seriously-ill sister.  So I did a second trip, this time to Giant.  Looks like Giant is slowly getting its act together, but only slowly.  And Giant customers are not.

It was a short trip.  Of Giant employees, I only noted one who was not wearing a mask, and that one had a mask, she was just wearing it to cover her mouth only, presumably so she could breath through her nose.  The majority of customers were masked.  But there were plenty of customers, no masks, more-or-less clueless about social distancing, paying no heed to the one-way aisles, and so on.  (Although, to be fair, Giant has not exactly gone out of its way either to highlight that those are one-way, or to enforce that in any way.)

Giant appeared quite well-stocked.  Whatever you may have heard about “meat shortages”, that was clearly not the case there.  Any cut of chicken, any cut of pork, any cut of beet, all the fresh fish you want, and so on.  Pretty much any part of any dead critter that you’d care to eat, they had plenty.

Dairy other than milk was still quite moth-eaten, and I can’t quite figure out why.  In the bourgeoisie cheese section (by the deli), you can get anything you want, in quantity.  But the proletariat’s cheese section (by dairy, other end of the store), it was a harsher world entirely.  You could find something, for sure, but definitely a hit-or-miss affair.  And none too deeply stocked, for what was present.

As an economist, that upscale-versus-downscale disparity made sense, if not equity.  But the cheese-versus-fresh-milk disparity, I can only guess that this is related to the rate of production.  Fresh milk is produced on a flow basis, cheese, yogurts, and similar take weeks to month to produce.  And yet, I’ve read that the US was (and still is!) facing a huge cheese surplus.  I suppose the current state of affairs reflects the lag in cheese production relative to milk.  I just found it to be an odd and rather stark contrast, given that it’s all based on the same raw material.

On the plus side, I finally scored some Tater Tots!  We don’t normally eat processed food like that, but for some reason, my family has taken a shine to Tater Tots during lockdown.  So I’m always happy to stumble across a bag.  It’s odd, what little things will make my day, in this new world.

Addendum:  Why I shop in person.  First, delivery slots remain congested.  Second, I take every precaution, including a proper mask, use of paper towels to avoid touching high-touch surface, and so on.  I do exactly as CDC recommend and wash hands before, upon return, and after putting groceries away.

And third, it’s really not clear whether there’s any risk at all.  That’s because there’s been no intelligent epidemiology that informs us as to where the new coronavirus cases are coming from.  (Other than cases attributable nursing homes.)

Think about the spaces in which you might plausibly catch coronavirus:

1. Within your home (from a family member)
2. In a public shopping area.
3. In a public dining area.
4. In a public outdoor recreation area.
5. In a public indoor personal-services or recreation area (gym, hair salon).
6. In a non-public shared work area (office, factory)
7. In institutional congregate living area (nursing home, prison, etc.)

We have good information 7 (nursing homes and prisons are high risk).

The Chinese experience suggested that the tail-end of the spread was mainly in 1 (within-family spread should be the last observed spread of cases).

We have piecemeal data on 6 (workplace), but only when there is some spectacular event (or string of events) such as has occurred at meat-packing plants.

But what your risks are, in those various public areas 2-5 (shopping dining, outdoor recreation, indoor recreation and personal services), nobody so far has given you even the faintest hint.  And that’s exactly what you’d like to know, as various states begin to re-open those area to a greater or lesser extent.

Plausibly, if aerosol transmission is a common mechanism (see front page for explanation), nobody ever will do that, because standard CDC-type contact tracing likely will not identify cases spread via aerosol transmission from asymptomatic individuals.  If so, those cases of infection will remain attributed to “community” (i.e., unknown-source) infection, and the CDC or state health department will never be able to give you even the faintest clue as to how safe or dangerous those areas actually are.

That’s a fundamentally poor way to go about making your personal safety decisions.  Let alone making state-level decisions on what to reopen, when.  But the world is what it is.