Post #1259: COVID-19 trend, ending the week

The U.S. as a whole is now 10% below the 9/1/2021 peak of the Delta wave.  We stand at 46.1 new cases / 100K / day, down from 46.6 yesterday.

A month ago, when I first tried to predict the peak of the Delta wave, and came up with “early September”, an astute reader suggested that the wave for the U.S. as a whole ought to be much “broader” than the waves for the individual states.  In hindsight, I’m going to say,  that seems to be correct.

Overall, for the past week, the number of new cases is essentially unchanged.  But that’s due to that big “divot” in the curve, depressing the case counts last week.  I’ve found no clear explanation for that “divot”.  At this point, I’m going to attribute it to an inexplicably large impact of the Labor Day holiday on testing and reporting of testing.  In the past, major national holidays produced impact of that size.  We’d just never seen anything like that before for (e.g.) Memorial Day, July 4th, or Labor Day.

If I airbrush that out, and bridge the gap, I get a plausible, if somewhat broad, shape to the peak.

In short, despite all my panicky posts of the past week, it appears that the U.S. merely continues to grind through the Delta wave.  Which, as of now, peaked on 9/1/2021.

As with prior waves, we’re seeing groups of state move into the U.S. peak position and then have their new case counts decline.

Florida, for example, has now fallen more than 50% since its 8/28/2021 peak of 112 new cases /  100K/ day, on the last day of August.  They are currently (9/17/2021 data) at 54.

The initial group of states that led the wave — FL, LA, MA — are all on the down-side of it.  We’ve had an intermediate group show up.  And now the three states with more than 100 new COVID-19 cases / 100K / day are SC, TN, WV.  It’s pretty clear that Alaska is on track to hit that.

The pandemic continues to show considerable geographic clustering.  If I separate out the states that had high rates, but appear to have peaked, I get the Gulf states, less Texas, pus Georgia:

Beyond that, it’s difficult to generalize about the next set of states — the states with high and rising case rates.  It looks like the southern Appalachians are represented, as is Alaska.  Not visible, Montana would also make the cut based on the current high rate of growth there.

So that’s how it looks today. The Gulf states (ex TX) seem to have peaked.  Fl, LA, MS are now at about half the rate of daily new cases that they were three weeks ago.  A couple of neighboring states (GA, AL) seemed to have peaked maybe a week later.

Now we just have to wait for this to work through the rest of the states.  And then, at some point, it will probably converge with a winter wave.

Updating the herd immunity table

I should update my “herd immunity” table.  This is my best guess at to the fraction of each state’s population that is immune to COVID-19.

This never did have much accuracy, owing to the need to make a couple of fairly critical (but nearly data-free) assumptions.  As time passes, it gets even less accurate, for two key reasons.

First, immunity fades.  That’s true of natural immunity (following infection) or immunity acquired via vaccine.  As the pandemic stretches on, it becomes increasingly dubious to count people who were infected a year ago, or vaccinated 7 months ago, as immune to COVID-19.

Second, widespread home testing with antigen (quick) tests likely reduces the fraction of the population of truly infected individuals that are formally diagnosed with COVID-19 and counted in the state data.  (Restated, increases the ratio of actual, total cases to diagnosed cases counted by state health departments.)

Those antigen tests don’t need to be sent to a lab, so they are not reported to state health departments.  And, near as I can tell, they appear to have a low false-positive rate.  All of that means that if you give yourself an antigen test, you don’t really need to do anything else, testing-wise.  Unless you did something to trigger a false positive (such as drinking an acidic beverage before testing), you can be fairly sure that you’ve got COVID-19 if you get a positive reading.  (By contrast, they have a fairly high false negative rate, so if you get a negative reading, there’s still a good chance that you do have COVID).

I think the magnitudes of both of those effects are unknown.  And I’m ignoring them for now.

So, FWIW, here are my “standard” assumptions, and the results I get (data is as of about a week ago).

  • Two un-diagnosed cases for every formally diagnosed-and-counted case.
  • Full vaccination is 84% effective against Delta, on average.
  • Partial vaccination is 54% effective against Delta.
  • Immunity from prior infection is 84% effective against Delta.
  • People get vaccinations at random, regardless of whether they have had a prior infection.  (I need this last one to net out the assumed overlap of the prior-infection and vaccination populations).

The table shows the estimated fraction of the population that is totally immune.  E.g., if there were 100 people fully vaccinated, I’d count 84 as being totally immune, based on the assumed 84% effectiveness of the vaccines.

Source:  Calculated from data on the CDC COVID data tracker, using the assumptions listed above.

I should point out a few things.

First, the high-immunity states are a motley crew.  It’s a mix of high-vaccination states, and high-cumulative-infection-rate states.

Second, the high-immunity states are not very well correlated with who is doing well and poorly right now.  In part, that’s because you might start to reach high immunity during the Delta wave.  In other words, if infection is rampant in your state now (as in Tennessee), that’s pushing you up this list.

Third, in this calculation, 80% is the magic number.  (Not 90+%, because I’ve already adjusted for the effectiveness of the vaccines.)  If the “R-nought” of the Delta variant is 5.0 (which seems to be somewhere around the consensus), then you need to have 80% fully immune to reach herd immunity (in the sense that the pandemic would die off even if you took no other precautions such as wearing masks, limiting social interaction, and so on.)

(Explanation:  If each infected person would infect five others absent an intervention, you need to block at least four of those new infections to get the pool of infected individuals to shrink.  Hence, R-nought of 5.0 requires 80% full immunity to achieve herd immunity.)

I’m just pointing out that, with all the shortcomings and assumptions and so on, this is the first time that any state has every reached what would be, in theory, the herd immunity number.  (Using my current (more refined) set of assumptions).

This is, in part, why my guess remains that we’re going to have a fairly bad winter wave this year, and then we’ll be done with this.  COVID-19 will always be lurking in the background, but it won’t be epidemic in the U.S.

Why? Project this table forward, using last year’s winter wave.  The U.S. had about 20 million diagnosed cases in last year’s winter wave.  That’s an estimated 60 million actual cases, under my assumptions, or about 18% of the U.S. population.  Start tacking 18%s to the numbers above, and everybody from Virginia on up would have hit the magic 80%.

In round numbers, best guess, one more awful winter wave should put the majority of the country at or near the herd immunity level for Delta.  Add in a few other factors that also interrupt infections (masking, limits on social activity) and we should at least be in the ballpark.  I hope.

Post #1258: William and Mary, wrapping up, total of 36 new cases for the week.

I’ve been asked to keep posting my tabulation of new COVID-19 cases at William and Mary.  Let me do this once a week, on Friday, assuming there’s nothing newsworthy going on.  You can’t recover the daily information directly from the  William and Mary COVID-19 dashboard.

That 36 cases is better than last week, but it’s still a bit high compared to college-age Virginians as a whole.  Using VA Department of Health data for those age 18-24, for this past week, at the all-Virginia age 18-24 new case rate,  we’d have expected 22 cases this week, for the roughly 6600 students on campus.  That does not account for differences in vaccination rate, testing rate, and so on between the William and Mary student body and the Virginia college-age population.  All it shows is that we’re somewhere in the ballpark of normal for a Virginia college-age population.


Post #1257: Town of Vienna revised zoning 1, building height along Maple


An odd thing happened yesterday.  I started to look at the draft of the new zoning regulations for Vienna Virginia, and I wasn’t horrified.  Yet.

The materials I’m looking at were provided for the September 1 2021 Vienna Town Council work session, at this link on the Town’s Granicus website.  I’m starting with those, and I’ll work my way to more recent materials as time allows.

There’s some turbulent history behind this rezoning, which I’ll recap below.  For now, all that Town of Vienna residents need to know is that the Town is redoing all the zoning, for the entire town.  And whatever the end result, it’s pretty much a certainty to be passed unanimously by Town Council.  (Because, despite it being illegal to take votes outside of Town Council meetings, somehow, Town Council votes seem to be determined ahead of time, and voting “no” in a Town Council meeting no longer seems to be allowed (Post #1132).

I’ve been putting off looking at the new zoning because I fully expected to be horrified.  I just couldn’t stomach looking at it.  Not after the rhetoric that was flying last year, at the start of this rezoning process.  The scope of work gave town staff carte blanche to change any and every aspect of zoning in the town (Post #481, Post #487).  Town staff were aiming for building sizes and housing densities that far exceeded anything permissible under prior zoning (Post #1123).  There was, as I recall, a completely goofy contractor’s report telling Vienna that, in effect, people who work in Vienna have to live in Vienna, and vice-versa, so that’s why they needed to zone for at least 100 dwelling units per acre, all up and down Maple Avenue (Post #1138).

With that as context, the Town website characterizes this town-wide zoning revision as “a tune-up” of the old zoning laws.   As well as stating that the zoning hadn’t changed in 50 years (conveniently tossing the now-rescinded (Post #706) Maple Avenue Commercial (MAC) zoning down the memory hole).  Meanwhile, everything else on the Town website regarding zoning is the usual peppy, upbeat, agitprop that was the hallmark of their presentation of MAC zoning to the public.

Against this backdrop, there was what I interpreted as some modest push-back from Town Council.  Here’s what I wrote at the time (Post #413):

Councilmember Potter said, in so many words, the voters gave us a mandate, and it wasn’t for larger buildings. I believe Councilman Springsteen used the phrase “mission creep”.

Given all that, I expected the worst.  I figured it was deja vu all over again.  I expected the Town to ignore the prior citizen unrest over the rescinded MAC zoning, and just plow ahead with MAC-on-steroids.

But that hasn’t happened.  At least, not based on the code contractor’s initial report (in the materials cited above).  It’s not the MAC-on-steroids that town staff were so adamant about a year ago.  It’s not the minimum 100-dwelling-units-per acre that their hired experts insisted on.

To the contrary, my impression is that Town Council and town staff seem to be aiming for some level of moderation in the new zoning.  I’m floored, because if you read the scope of work for this task, and what was said at the outset, that clearly is not where Town staff were coming from a year ago.

There are still things that run contrary to what I believe the town’s citizens would like to see.  And things that are objectionable from the standpoint of the taxpayer.  There are some ambiguities, which in the past meant deliberate ambiguities designed to provide loopholes.  And the Town remains completely, nuttily inconsistent with regard to automobiles, parking, and alternative forms of transport.  But that’s all to be expected.

For now, I’m going to put those caveats aside, take the proposed rezoning at face value, and assume this is being written and presented in pure good faith.  Nothing up their collective sleeve.  I hope.

Let me start with what I believe to be the two key issues to keeping the Maple Avenue area livable:  Building height and number of allowable floors.


Proposed commercial building height along Maple: Background

The most objectionable aspect of the now-rescinded MAC zoning is that the building were big.  At least, big in the context of what’s here now.  They were objectively different from the existing “small town Vienna”, as I showed in a survey of 100 disinterested U.S. adults (Post July 14, 2018).

For example, the roughly 150-apartment MAC building being constructed up the street from me (444 Maple West/Tequila Grande) will be, by far, the single largest commercial structure on Maple Avenue. 

Source:  444 Maple West MAC proposal to the Town of Vienna.

That building — approved under MAC zoning — will enclose more than twice as much volume as the entire Giant Food shopping center, from Giant down to Advance Auto, currently the largest commercial structure on Maple.


Yet it sits on a property that’s about one-fourth the size of the Giant Food Shopping Center.  As a result, it’s going to place a whole lot of people, into a very compact space, compared to the adjacent neighborhoods.  (With no southbound egress to Nutley, so it’s a sure bet those new commuters will be coming down my quiet, narrow, sidewalk-less residential street, where the Town has made it crystal clear they will do nothing to moderate that additional traffic.)

Above:  Typical pre-pandemic AM rush hour at 444 Maple West.

Within that overall bigness, the allowable 62′ overall building height under MAC zoning was a focal point.  The neighbors objected in part for the visual aspects of that.  But in addition, with height comes density.  Taller buildings mean more floors, and mean that you can pack more people onto an acre of ground.  The denser the population, the more problems the neighbors will have with (e.g.) more cut through traffic, and more light/noise pollution associated with the building, its occupants, and their movement to and from the building.

With the stroke of pen, Town Council doubled the population density of my little corner of Town.  Left is a (slightly outdated) count of dwelling units from that one new building, compared to the entire adjacent neighborhood.  Imagine zoning the entirety of Maple for that level of housing density or higher?

Let there be no revisionist history regarding the unpopularity of this with the average citizen of Vienna.  Here were the results of dueling on-line petitions at that time.  Even though voluntary internet surveys and petitions are not a legitimate means to assess the true cross-section of public opinion, the difference in the response in this case is fairly stark.

And in the following Town Council election, it seemed as if the citizens of the Town spoke pretty clearly (Post May 8, 2019).  It was the largest turnout for a Town election up to that point. Among other things, an incumbent lost a seat, which is all-but-unheard of in Vienna, and a candidate strongly endorsed by an incumbent lost a seat.  Three strongly anti-MAC candidates are at the top of the list.  It was nothing short of a referendum on MAC zoning.

And, eventually, more than a year later, the MAC statute was eventually rescinded, with what struck me as a truly unnecessary bit of flirting with deadlines (Post June 2, 2020).  But, duly noted, I was a businessman, not a politician.

Proposed commercial building height along Maple:

It’s 20′ shorter than MAC zoning,

It’s arguably 7′ taller than existing commercial zoning.

With that as background, how does the proposed zoning compare to existing commercial zoning along Maple, and to the now-rescinded MAC zoning, in terms of allowable building height? 

Obviously, that’s going to be a key determinant of dwelling unit density, and all the spillover problems that brings.  If limit buildings to three floors, with no housing on the first floor, you get two floors of dwellings.  With four floors, you get three floors of dwellings.  That seemingly innocuous difference results in a 50 percent increase in dwelling-unit density.

But as importantly, to an economist, it’s not just the physical limit that lower building height implies, its the economic limit.  Shorter buildings reduce the economic incentive to tear down the existing Vienna downtown.  It allows more existing buildings to stand, based on their profitability relative to conversion to housing.  And so it slows down the pace of development.  The right way to think of it is that it gives more current property owners the choice to hold onto what they’ve got.  A choice that would not be economically viable if there were larger profits to be made in converting the existing retail establishments to “mixed use”, that is, medium-density housing developments with some retail.

The current commercial zoning on Maple has a height limit of 35 feet.  But there’s a catch.  That’s just to the flat roof of the building.  You can have projections above that.  Some of those projections above the roof are designed to be seen (generically termed “architectural elements”, I guess).  Other projections are just ugly equipment, that you can still see.

Using the altitude function of Google Earth, you find the height by paying attention to the altitude reading (lower right corner) as you mouse over a building and the adjacent parking lot.  Using that approach, you can easily find buildings on Maple whose actual ground-to-highest-point height exceeds 35′.

As an example of architectural elements well over 35 feet, the former Rite Aid (now Dollar General) is just about 48′ to the top of its signature tower.  The flat white roof sits at 35′ above ground level.  But the surrounding brown parapet and the tower go far above that.



As an example of HVAC equipment, the former office building at 380 Maple Avenue West (Wade Hampton and Maple) that was recently torn down was 35′ to the flat roof, but 44′ to the top of the HVAC equipment that sat on that roof.

The point is that, under current zoning, the interior space — the living space, more or less — is limited to 35 feet in height.  But the exterior of the building, including either architectural elements or visible roof-mounted equipment, can be considerably higher than that.

(And yet, neither building looked exceptionally large from any angle.  That’s because they sit far back from the road and adjacent neighborhoods.)

The new zoning will allow 42′.  But unlike the current zoning, that’s to the top of the building, not to the flat roof.  The current wording appears to say that any projections that are part of the building’s architecture have to fit under that 42′ limit.

(But, to be clear, these new buildings will appear much larger than what they replace.  That’s because, unlike the older buildings, they are going to cover the lot, and sit right up next to the road.  You’ll lose the buffering of the surrounding parking lots.)

My reading is that the proposed zoning ignores the height of HVAC or other equipment on top of the building.  (There is no mention of it, and in the industry in which I used to work, such items would be classed as fixtures, not building).  If I have that right, builders could place a flat roof at 42′, and put their unshielded HVAC equipment on top of that.  From any perspective where that is visible (as it was at 380 Maple West), such a building could appear significantly taller than 42′.

The proposed zoning has an exception to the height limit that applies in the very center of town, where the commercial lots do not abut residential areas.  There, they would allow another 12′ of height for “rooftop uses”.  (The example given is a rooftop dining area).  That section of the proposed zoning seems loosely written at present.  But, a) I don’t live next to that area, and b) the plain reading seems to rule out using that 12′ for another floor of housing.  So that’s not a huge concern for me, and maybe I’ll look at that some other time.

Under the rescinded MAC zoning, the equivalent maximum building height was just over 62′.  It was 54′ to the flat roof, plus an allowance for parapets and such.  I am not sure whether everything — including HVAC equipment — had to fit under that height.  (For example, the HVAC equipment on the MAC-built Chick-fil-A/Car Wash is plainly visible from the road as you enter town.)  But, for sure, all of the building’s architectural elements did.

In summary, the proposed 42′ building height limit along Maple …

  • Is 20 feet shorter than the now-rescinded MAC zoning, as measured to the top of the building itself, including parapets, projections, and so on.
  • Is an unknown amount shorter, to the highest visible point, if HVAC equipment is allowed to project up above a 42′ roof and be visible.
  • Is arguably 7 feet taller than existing commercial zoning.  That’s arguable because the existing zoning doesn’t include parapets and other architectural elements within that limit, but the new zoning does.
  • Is an unknown amount shorter, to the highest visible point, if HVAC equipment is allowed to project up above a 42′ roof and be visible.
  • Can be increased to 54′ for “rooftop uses” in the very center of town, where the commercial lots are not adjacent to residential areas.
  • May allow for buildings with about 20% larger interior volume than are possible under current zoning.  The regulation appears to leave open the possibility of having the flat roof of the building at 42′, with HVAC equipment allowed to project an undetermined amount above that.  If so, that’s a 20% increase in above-ground interior volume for the same building footprint.

Proposed number of stories allowed:  Not specified?

Another aspect of MAC zoning that left a bad taste in many people’s mouths is the issue of floors or stories.  This issue is key for housing density, but it also has to do with promises made and broken under MAC zoning.

Obviously, the more floors in the building, all other things equal, the higher the housing density.  And once you realize that the zoning won’t allow housing on the first floor, you realize that adding a fourth floor increases housing density by 50 percent, relative to a three-floor building.  You go from two floors of housing, to three.

Near as I can tell, the draft zoning discusses this as if three story buildings are a given.  But, again, near as I can tell, they don’t explicitly say that.  I don’t see an explicit statement that buildings along Maple, under the new zoning, can have no more than three floors at ground level or higher.

If that’s left ambiguous, I think that’s an easily-remedied mistake.  Just specify a three-floor limit, in addition to specifying height.

There’s a historical reason for that.

MAC zoning was sold with the promise that the buildings would only be four stories tall.  That was literally written into the code.

And, each in their own special way, developers, town staff, and (by rumor) at least one Town Council member did their best to gut that promise.  The rule doesn’t apply because of this-and-so.  So long as there is the appearance of four floors, that’s fine.  Oh, this thing that looks like a floor, that’s not really a floor, you are mistaken, because the rules applying to commercial floors don’t apply to residential floors.

In other words, there were flagrant attempts to game the four-floor limit under MAC.  Even though the plain language of it appeared quite clear.

That experience with MAC zoning made it perfectly clear that if you don’t have an airtight rule regarding the number of floors, somebody will take advantage of that.  Or, at least, try.

And so, to all the people who will say, oh, that’s not necessary, it’s not possible to fit four floors in 42 feet, builders wouldn’t do it because it wouldn’t be commercially viable, and on and on.

To all those people, I say:

“Great.  If that’s true, then there’s no harm in making a three-floor limit explicit in the zoning rules.”

Because, if they could squeeze five floors into the MAC 54-foot height limit, I really can’t see how much more difficult it would be to squeeze four into the proposed 42 foot height limit.  In particular, I have not yet seen anything equivalent to the MAC rule that all first-floor retail had to have minimum 15 foot ceiling height.  Absent that, it would seem perfectly possible to squeeze four floors into 42′.

And if you allow that, then we’re right back to a MAC-level housing density along Maple.  Which is, I think, something this new zoning is attempting to avoid.  So, I, for one, would like to see an explicit, no-exceptions, air-tight three floor limit.  If that’s redundant, then I’m happy to wear belt and suspenders.

Above all, we can’t rely on the descriptions and the drawings, all of which refer to three-floor buildings.  All the illustrations for MAC showed cute little three floor buildings as well.  Those drawings have no force of law.

Write it explicitly into the code, please.  Some of us still have trust issues after MAC zoning.

My final word here is that the height isn’t everything.  I don’t want to give the false impression that there’s no real change here.  The main change is opening up Maple as a medium-density housing area.  That’s the money that will drive the change, result in replacement of smaller older buildings with new buildings that have much larger interior volume.  So we are going to get bigger buildings, and that is going to be driven by the zoning change.  They are going to appear much taller, due to the loss of the buffering parking lots.  But, purely as a matter of fact, they aren’t going to be much taller than the tallest commercial buildings already on Maple.

Once you’ve bought into using Maple Avenue as a housing district — as the Town of Vienna appears to have — you’ve got to take your victories where you can.  And conditional on that, lower building height (versus MAC zoning) should moderate the persons-per-acre density of the new housing that will be built.

A few other things to note.

The new zoning along Maple is specified as zoning for the core of the downtown, and then, separately, zoning for the east and west ends of Maple.  Near as I can tell, the east and west ends are identical.  The core of the town, however, has provisions for additional height and additional by-right uses.

Of particular interest to me, medium density housing is a conditional use on the ends of Maple, not straight-up by-right.  In the middle of town — mostly but not entirely away from the residential neighborhoods — using the upper floors of a building for apartments or condos is given as a right.  Any building meeting the zoning requirements and the building code can do that.

But it looks like apartments and condos are a conditional use on either end of Maple.  That doesn’t mean they aren’t going to happen.  It just means that there will be some public discussion of them before they happen, because the Town has to issue a “use permit” to allow them to proceed, and that requires a public hearing.  So you’ll at least be apprised if one of those is going up near you, on either end of Maple.

Source:  Town of Vienna code.

Otherwise, if you step back from it, the proposed revisions of the existing zoning actually look like revisions of the existing zoning.  By that I mean, not wholesale replacement, as was the case with MAC zoning.  It looks like the Town will modestly expand the height of allowable buildings somewhat. Allow more uses.  Probably skimp on the parking requirements, relative to what’s required now.

By far the most profound change is the one you’re not allowed to question:  Medium density housing.  The current commercial zoning is just that — you have to use the majority of the building for commercial (non-residential) use.  That’s going to be tossed.  And that decision apparently cannot be rescinded, not even questioned.  The voracious demand for housing in Northern Virginia is what will drive the construction of the new, large, “mixed-use” buildings — apartments and condos, with first-floor shops — on Maple.

Of the additional rules they are imposing, the one I like the least is that they’re still writing the zoning in a way that will eventually create a “commercial canyon” on Maple, assuming enough redevelopment.  That is, they are banning front-of-the-store parking, and effectively requiring that the facades of new buildings be located 15′ from the curb.  This will eventually give a much more “urbanized” look to Maple, compared to the visually empty parking-lots-with-offset buildings that we have now.  Currently, the view on Maple is mostly open sky, and you can see the trees in the neighborhoods behind buildings offset from the road.  In the future, with this plan, you’ll see building facades.

Otherwise, it looks like the “open space” rule along Maple will  be as ineffective as it was under MAC (Post 7/12/2018).  So you should expect to see buildings that cover the lot, or come close, as is true with the two MAC buildings in my neighborhood.  Assuming they calculate it as before, for most of the lots, the sidewalks, walkways, and little bits of standard greenery will more than satisfy the “open space” requirement.

Source:  See this post for full writeup of methodology.

That is, I think, where the proposed revision falls most short of what the people of Vienna wanted out of a rezoning of the commercial district.  When I did my small random-sample survey of Vienna residents (still the only one that has ever been done on this topic), overwhelmingly, what they wanted to see out of MAC zoning was more open space and more green space.  As shown above.

But open space costs money, for the foregone profits you could have had from building on it.  In the end, rather than trying to obtain that via more-or-less a taking of private property, maybe the Town would be better served in finding more land for open space, at lower total cost, near Maple and across Vienna.  Near as I can tell, that seems to be the plan at present.

Post #1255: COVID-19 trend to 9/15/2021

New COVID-19 cases are up 3% over the past seven days.  But we’re still 4% below the 9/1/2021 peak of the Delta wave.  Currently, we’re at 47.3 new cases / 100K / day, down from a revised 47.9 cases yesterday.   The overwhelming majority of states showed an increase in new COVID-19 cases over the past seven days.

Here’s my regional graph in logs and natural units.


Data source for this and other graphs of new case counts:  Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 9/16/2021, from”  The NY Times U.S. tracking page may be found at

In the log graph, it appears that the nice orderly structure of the Delta wave is starting to break down.  For the past month, the regional trends formed a set of (near) parallel lines.  That is, the regions had similar rates of growth in new COVID-19 cases.  That’s starting to get lost as you get to the right side of the chart.

If we compare the first and second years of the U.S. pandemic (below, graph starts April 1 of each year), this last little episode just looks like a post-holiday blip.  E.g., the wiggles in last year’s winter wave (tallest part of the blue line)  were due to Thanksgiving and Christmas/New Year holidays, respectively.

That problem with that hypothesis is that Labor Day is nowhere near as big a holiday as Thanksgiving.  Which is what appears to be case on the chart above — the “hook” on the end of the red line is about as deep as the first wiggle on last year’s winter wave.  On the other hand, data reporting was more continuous last year.  States weren’t taking the weekends off, as is now commonly the case.  Maybe a minor holiday, combined with sporadic data reporting, can produce that much of a disruption in the numbers now.

But the bottom line is that I can’t find any solid evidence, so far, that this latest change is being driven by anything in particular.

There is no systematic data source that lets me look at cases by age in a timely fashion, so the idea that this latest change is due to schools can’t be tested.

And as for the onset of the winter wave, it’s just too soon to tell.  Growth in daily new COVID-19 cases has definitely shifted into the northern half of the country, as you can see below:

Map courtesy of

That's a lot clearer if I simplify the map to just three colors, below.  Now, with the exception of Louisiana and Illinois, the separation of the states is quite stark.

Map courtesy of

The upshot is that I've gone from having a pretty solid prediction for the last month, to being totally lost as of today.

One option is that this is just a post-holiday disruption of testing and reporting, as we saw happen last year.  But it's grossly disproportionate to the size of the holiday, compared to last year.  And the regional lines are starting to get disorderly, which is what has happened in the past at an inflection point in the curve.

A second option is that this is due to school re-opening.  But there's no hard data yet, on a national level.  All I can get is newspaper reporting, and the occasional state where cases are reported by age.  In Virginia, where I can get the data, there appears to be no upsurge in cases for school-aged children.

Yet a third option is that this is the start of the winter wave.  New-case growth has shifted to the northern half of the country, as it did for last year's winter wave.  But it's at least a month too soon for that to start happening, compared to last year.  On the other hand, Delta is substantially easier to spread than the native variant that was prevalent last year.  So maybe that shifts the timing.

We'll just have to wait and see.

Post #1254: Update for William and Mary: That’s good.

The William and Mary COVID-19 dashboard doesn’t track day-to-day changes.  That’s why I’ve been writing down each day’s numbers, as shown above.

Last night’s update showed three new cases.    That’s unremarkable.  It’s just about the rate you’d expect for an average college-age population in Virginia.

Given that, I’m not going to post about this for a while, unless there’s some material uptick in the new case numbers.

Good news is no news, or something like that.

Post #1253: COVID-19 trend to 9/14/2021, not according to plan.


The Labor Day holiday scrambled the data on new U.S. COVID-19 cases.  Today, that should all have been sorted out, and we should get a clear look at the trend.

Unfortunately, the trend looks ugly.  Today the U.S. stands at 47.3 new COVID-19 cases / 100K / day, up two from two days ago. The case count is right where it was one week ago. Continue reading Post #1253: COVID-19 trend to 9/14/2021, not according to plan.

Post #1252: COVID situation at William and Mary appears to settle down


Last night’s update of the William and Mary COVID-19 dashboard showed just over 46 new positives for the prior three days.

Last year, when William and Mary itself was doing all the testing, it was hard to interpret the Monday count.  The numbers had a strong up-and-down pattern over the course of the week, presumably reflecting W&Ms schedule for routine testing.

But now, by contrast, most (possibly all) of what we are seeing is testing for cause.  The new COVID cases above are a mix of individuals who had themselves tested ( and reported a positive test to W&M), and symptomatic or known exposed individuals who are being tested by W&M and found to be positive.

(At some point, there will also be ongoing screening testing of the unvaccinated.  And, later in the semester, W&M will test a random sample of students to estimate the prevalence of COVID-19 on campus.  But for now, I think it’s mostly diagnostic testing, that is, testing for cause).

Based on that, my guess is that the test results are coming in a fairly steady stream right now.

If that’s true, we can tentatively say that the low number of new positives, per day, for the past three days, is an indication that the true rate of new positive cases per day has backed down from last week’s peak.

Obviously, there’s not enough information there to declare victory.  But, arguably, there’s enough to declare non-disaster.  As of today, it doesn’t look like this is any sort of out-of-hand rapidly-escalating mess.  


Post #1251: COVID-19 trend to 9/13/2021, I can’t fix the data today

Whatever U.S. COVID-19 case count you see today is either going to be grossly wrong or partly fictional.  Maybe both.  Mine included.

My best guess is that the U.S. Delta wave continued to recede slowly over the weekend.  But that is just a guess.  We won’t really have any hard data on that until tomorrow at the earliest.

This post explains the problem with today’s data.  It’s clear that the raw data aren’t usable, and I can’t quite seem to come up with a fix.

Continue reading Post #1251: COVID-19 trend to 9/13/2021, I can’t fix the data today

Post #1249: A first-hand lesson on why we still have a pandemic

Source:  Wikipedia

Yesterday, my wife and I got onto a bus packed with un-masked strangers.   When we got to where we were going, we spent some time in indoor spaces packed with loud crowds of eating, drinking, non-masked-wearing strangers.  Then we got back on that bus and went home.

In hindsight, this may not have been the smartest thing we ever did.  It takes just a little math to realize it’s a pretty good bet that some COVID was spread at the event we attended.

It wasn’t our intention to do that.  It never is, I guess.  All I really wanted was a nice plate of pirohi.  What I got was a lesson in why we’re still in a pandemic.  Or, at least, in how thoughtless the average American is.

Continue reading Post #1249: A first-hand lesson on why we still have a pandemic