Post #1161: COVID-19 trend to 6/17/2021, where’s Delta?

The overall trend of new COVID-19 cases continues downward for the U.S. Whatever impact the new Delta COVID-19 variant is having, it’s not large enough (yet) to offset the pre-existing trend.

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 6/18/2021, from”  The NY Times U.S. tracking page may be found at

As I was updating my graphs, I noticed that one state stands out for having a strong upward trend in new cases:  Missouri.  That’s quite the outlier, given that every other state in that region shows a fairly consistent downward trend.  

That also rang a bell.  The last time the CDC published data on incidence of variants by state,Missouri stood at the top of the list for incidence of the Delta variant. 

Source:  CDC COVID data tracker.

There are a few caveats for the table above.  First, those data are based on a small sample and so likely have a lot of uncertainty in the estimated incidence rate.  Second, that’s ancient history.  The average date for those sequenced samples would be the first week of May.  Given the less-than-two-week doubling time of incidence of the Delta variant, the incidence now should be maybe 6 times higher than what is shown.

I then searched systematically for all the states with strong and consistent upward trends.  In particular, I looked for states that had both one-week and two-week trends in excess of a 20% increase in cases per week.  Only two other states met that criterion, other than Missouri.  And, again, somewhat oddly, they were geographically clustered.  A handful of other states had smaller or less consistent upward trends.  But only these three had a strong and consistent upward trend for both of the past two weeks:

Then I read the news, and found that there’s a COVID-19 outbreak in Southwest Missouri that is being attributed to the Delta variant.

The reporting is not quite deja vu all over again.  Sure, hospitals are filling up, emergency departments are overloaded, and so on.  That’s familiar.  But this time, we have a vaccine, the patients are almost entirely un-vaccinated individuals.  In the words of a local hospital administrator in that area, what you you waiting for?

“Bed capacity is strained. ED waits are long. COVID patients are younger, sicker and unvaccinated. Vaccines are free, available and effective. What are you waiting for? 82? 102? 152? What about 1? 1 person you care about? You?”

Source:  Saint Louis Post Dispatch., emphasis mine.

Based on that reporting, Delta is now my far the most prevalent variant of the virus in Southwest Missouri.  The virus doesn’t respect state boundaries.  It doesn’t take much of an imagination to connect Southwest Missouri to states south and west of Missouri, per the map above.

Maybe this will be an isolated outbreak.  Or maybe its a harbinger for the U.S. fifth wave of COVID-19.

Before this U.S. outbreak, the only information to guide a prediction came from Great Britain.  The recent uptick in cases in Great Britain has been attributed to the spread of Delta, despite an ongoing partial lockdown.

But now we have the example of southwest Missouri.  The high incidence of Delta in Missouri was known more than a month ago.  It’s now the dominant strain in southwest Missouri.  And there’s a fresh COVID-19 outbreak there attributed to that variant that is now straining the capacity of the local hospital system.

One thing we can be sure of:  If we have another COVID-19 wave of any consequence, we’ll owe it entirely to the dumbasses who won’t get vaccinated.  Right now, vaccinated individuals account for 53 percent of the U.S. population, but only one to two percent of the U.S. COVID-19 hospitalized population (reference 1, reference 2).  More-or-less, vaccination appears to confer a fifty-fold reduction in the odds of being hospitalized with COVID-19.  The vaccines are that effective at preventing severe illness.

Source:  CDC COVID data tracker.

The trend of vaccinations picked up a bit in the past two weeks.  We’re still vaccinating at a rate in excess of 1 million doses per day.

We can quantify the degree of vaccine slacking in the US by measuring the number of doses that could have been given, if we’d kept up the highest demonstrated pace.  As illustrated below, that works out to an average of 1.5 million doses not administered for the past 60 days, or another 90 million doses that could have been given, but weren’t due to lack of demand.

The 53 percent of the population vaccinated could have been, in theory, 80%, if we had merely kept up the pace.  Just something to bear in mind of we end up with a Delta-drive fifth wave.


With these reasonably effective vaccines, we’re no longer at the mercy of the virus.  Instead, we’re at the mercy of the intelligence and public-spiritedness of our fellow citizens.  You’d hope we’d be coming ahead for that change, wouldn’t you?

Post #G21-033: 1000 growing degree days and the squash vine borer


She’s back.

I would love to think of gardening as something that’s done by the calendar.  Plant your peas (and potatoes) on St. Patrick’s Day.  Don’t plant tomatoes before Mother’s Day.  Mind your mayflies and your June-bugs.

And similar folkloric claptrap.

In reality, it’s all chemistry.  Chemical reactions occur faster in warmer temperatures.  Insects emerge after a given number of “growing degree days”, like the little biots that they are.   The warmer the year, the sooner they arrive.

Any correlation with specific calendar dates is based on a) your local climate, and b) the stability of that local climate.  Of which, for b), not only do things vary from year to year, but we really can’t count on having a stable average from decade to decade, at least not for U.S. gardening hardiness zones.

All of the above is an arch way of saying that I’d been stupidly expecting to see the squash vine borer (SVB) in early July.  Because that’s when I saw her arrive last year. 

But surprise, she’s here now.  Showed up in my garden today.

If I’d been paying attention to cumulative growing degree-days, via Cornell University’s tracking, I would have known that we passed 1000 degree-days — the point at which the SVB emerges — this past week:

And so, like clockwork, she’s back.

You can see everything I learned about the SVB last year, in Post #G27.

Starting about five days from now, I’ll be spraying spinosad on the stems of my summer squash.  In addition to killing as may SVBs as I can via the “hand clap” technique.  All this, in the hopes of extending my summer squash season for a few more weeks, until the powdery mildew and other diseases and pests overwhelm my squash plants.

At any rate, the upshot of this is that if you are in Zone 7, and growing summer squash, pumpkins, some types of winter squash, or melons, you need to be aware that the SVB is up and about.  It takes maybe a week for the SVB eggs to hatch, maybe a week for the resulting larvae (borer) to start killing your plants.  There are plenty of remedies suggested on the internet.  I found that weekly spraying of the cucurbit stems with high-strength spinosad worked for me last year.  That’s what I’ll be doing again this year.

Post #1160: COVID-19 Delta variant bodes for a 5th U.S. COVID-19 wave


If you can’t beat ’em, rename ’em.

If you track trends in COVID-19, you’re probably well aware that a new variant has taken over Great Britain and is in the process of taking over the U.S.  This is the COVID-19 variant formerly known as “Indian”, B.1.617.2.  Henceforth to be called Delta.  The British variant is now Alpha.

In this post, I’m getting my thinking straight about the new Delta variant.  Best guess is that, as with Great Britain, we’re going to get another wave of increased daily new case counts from the spread of the Delta variant.

Delta makes herd immunity effectively impossible with current vaccines alone.

I’m fairly sure this cheery bit of new is correct.  I’m almost equally sure you aren’t going to see anyone in our public health establishment saying it in public.  But math is math, and this new variant brings a double whammy.

  • The virus is more contagious
  • The vaccine is less effective

Practically speaking, those two factors put herd immunity via vaccination out of reach for the U.S.

Briefly recall how this works.  A pandemic will eventually collapse if each infected individual goes on to infect an average of less than one new individual.  If you can get that to happen, each round of newly-infected individuals is smaller than the last, and the pandemic shrinks away.

Now recall “R-nought” and the classical definition of herd immunity.  R-nought is the number of individuals each infected person would go on to infect, if there were no protection or immunity within the population.  For example, if each infected person would normally go on to infect three others (R-nought of 3.0), you need to interrupt at least two-thirds of those infections to bring the pandemic to a halt.  If R-nought is 10, you’d need to interrupt 90% of those infections to bring the pandemic under control.  And so on.

The more infectious the virus, the more people need to be immune to it before you achieve herd immunity.  Or the more COVID-19 hygiene protocols need to be enforced to cut off what would otherwise be chains of infection.

(I need to put a marker down here.  Epidemiologists always discuss this solely in terms of preventing new infections via vaccination.  But prior infections also confer immunity.  And good COVID-19 hygiene also prevents infections.  In reality, all of those factors work to interrupt would would otherwise be chains of disease transmission, and so all of those factors matter in a herd immunity calculation.  But for the rest of this section, I’m going to do what all the epidemiologists do, and pretend that the only way to interrupt chains of infection is via vaccination.)

The first key fact is that the Delta variant is more infectious than the Alpha variant which is more infectious than the original strain.  Rather than try to daisy-chain all those imprecise numbers, I’m just going to take somebody’s estimate.  Like so, from this seemingly-plausible reference, where R0 = “R-nought”:

Professor Cheng said last year's Wuhan strain had an R0 value of around 2.5, the Alpha strain was about 3.75 and the Delta strain was about 5.

That means if we were living life like we were in 2019, one person with the Delta strain would likely infect five other people, compared to just 2.5 last year.

I’m sure there’s considerable uncertainty around that estimated R-nought of 5.0 for the Delta variant, but I’m just going to accept it as a fact.  (You can find apparently legitimate sources suggesting a much higher value.)  And so, if each each infected individuals would natively infect 5 others, you have to interrupt four out of five of those infections to bring the pandemic under control.  In other words, with the estimated R-nought of 5.0 for the Delta variant, we now need to have 80% of the U.S. population immune to it before we have any hope of it going away.

The second key fact is that the vaccines are less effective against this strain of COVID-19.  The Pfizer vaccine is 88% effective against the Delta variant after two shots.  But, for the U.S., nobody knows how effective the Moderna or Johnson and Johnson vaccines will be.  Fauci guessed that Moderna will be about as effective as Pfizer, but that’s just a guess.  The AstraZeneca vaccine, commonly used in Great Britain, is only 60% effective against the Delta variant.  (The Pfizer and AstraZeneca numbers are based on this study.)

If vaccination were the only way to stop this, between those two factors, we would require at least 91% of the U.S. population to be vaccinated before we could achieve herd immunity.  (That is, .91 x .88 = .80, the level of immunity required for herd immunity against the Delta variant.   Re-stated, 91 percent of the population, vaccinated with an 88% effective vaccine, would stop 80 percent of the chains of infection.)

Short of vaccination-at-gunpoint, that’s not going to happen.

(There are some nuances here.  Probably, you are less likely to transmit the disease, if infected, if you are vaccinated.  And people will continue to achieve immunity by recovering from infection.  But in terms of your textbook herd immunity calculation, herd immunity is pretty clearly out of reach for the U.S. population.)

In practice, two things happen when you try to calculate where we stand on herd immunity with the Delta variant.  First, your estimate of the existing level of immunity falls, because the existing vaccinated population has less immunity to this new strain than it did to the existing strain.  And then, separately, the fraction of the population that needs to be immune goes up.

Again, between those two factors, there’s a world of difference between the way the U.S. looked against the Alpha (British) variant, and how it now looks against the rapidly-spreading Delta (Indian) variant.

Let me now redo my herd immunity chart.  This still assumes that you have complete immunity once you’ve recovered from infection.  I’m not changing that for now.  I’m only changing how effective one and two vaccine shots are.

Alpha variant (what we have now, the British variant).

  • R-nought = 3.75
  • Herd immunity goal = 73% immune
  • Current estimate = 64% immune.
  • Additional full vaccinations required = 9.5% @ 95% effectiveness

Delta variant (what is coming, Indian variant).

  • R-nought = 5.0
  • Herd immunity goal = 80% immune
  • Current estimate = 59% immune.
  • Additional full vaccinations required = 24% @ 88% effectiveness

As I said, double whammy.  We need more immunity to achieve herd immunity, and we instantly have less immunity, because the existing vaccinated population has less resistance to this new strain.

Where do we stand on the Delta variant and its growth

Let me first quickly benchmark Great Britain’s latest outbreak.  Currently, the Delta variant accounts for almost all (90 to 94 percent) of new cases in Great Britain.  At about 7000 new cases per day in a population of 66 million, that’s about 10 new cases / 100,000/day, with a strong upward trend.  And that’s despite significant restrictions on public life and public gatherings in Great Britain.

That compares to the current U.S. rate of about 4 new cases/ 100,000 per day.  And a slight downward trend.  With, as far as I can see, roughly no restrictions on public life left in most U.S. states.

The vaccination situation in Great Britain is roughly comparable to that of the U.S.  Fully-vaccinated individuals in Great Britain account for about one percentage point more than in the U.S., and Great Britain has injected about 14% more total doses per capita.  But a) a large share of their vaccinations are the AstraZeneca vaccine, which is less effective than Pfizer against the Delta variant, and b) those with just a single shot of vaccine receive little protection against the Delta variant (one shot of vaccine is about 33% effective).

The U.S. has the edge in terms of total reported cases per capita so far.  Presumably, those individuals add to the pool of persons immune to COVID-19. In the U.S., over 10 percent of the population has been diagnosed with COVID-19, versus about 7 percent of the population of Great Britain.  For each diagnosed person, there is probably another 2 to 3 persons who had COVID-19 but were not diagnosed.  (All of those statistics would depend strongly on test availability and testing behavior.).  Thus, the U.S. plausibly has an additional 10 percent of the population immune via recovery from infection, compared to Great Britain.

(FWIW, I looked up all of those statistics, I’m just too lazy to provide citation as to source for every one of them, as they are just background.)

What fraction of new cases is accounted for by the Delta variant in the U.S.?  This is a number that is changing rapidly, so you need to pay strict attention to the dates.

As of the two-week period ending 6/5/2021, the CDC estimated that the Delta variant accounted for just under 10% of all new cases in the U.S.

Source:  CDC COVID data tracker.

The doubling time for these cases in the U.S. appears to be something less than two weeks.  (The last three sets of CDC two-week observations or projections were 1.2%, 2.5%, and 9.9% of new cases.  In each two-week period, the fraction of new cases attributed to Delta more than doubled.)

Without bothering to define it, the case-weighted midpoint date for that two-week period ending 6/5/2021 is about 5/31/2021.  (The 9.9% is the average for the entire period.  It was less than that early on, greater than that later.  The date of  5/31/2021 is my best guess for the day, over that period, when the fraction literally hit 9.9%.)  That was more than two weeks ago.  Hence, we should add just over two weeks’ growth to that estimate to project forward to the rate as of 6/15/2021.  So, something in excess of a  doubling of those cases.

Best guess, by that calculation, somewhere around one-quarter of new US COVID-19 cases on 6/15/2021 were the Delta variant.  At that rate, it should be the most common strain of the virus in the U.S. by the end of this month.

Is it different this time?

The U.S. fourth wave was due to the growth of the British (now Alpha) variant, moderated by the rapid increase in vaccination.  It was a race, and back in early March (Post #1051), I used the best available data to project that vaccination would win.

I emphasize that to demonstrate that I’m not some nervous Nellie who cries “wolf” at any pretext.  The numbers reasonably clearly indicated that at the then-prevalent rate of new vaccinations, and the known efficacy of the vaccine, we’d be able to vaccinate enough individuals to stifle a major outbreak of the British (Alpha) variant.

But now?  Now we’re bringing in a variant that is yet-again as infections relative to Alpha, as Alpha was to the original COVID-19 variant.  But now,

a)  There’s no big build-up of vaccinations to offset that.  To the contrary, the U.S. vaccination rate is down to 1M per day.

Source:  CDC COVID data tracker.

b)  We’re dropped the greater portion of our COVID-19 hygiene at the CDC’s direction.

c) Good luck getting people to mask up again in case this gets ugly.  What are the odds that the CDC will be able to pull a timely about-face and tell us to put our masks back on, and then have Republican governors follow that advice, let along the U.S. population as a whole?

and finally,

d) The lower efficacy of the vaccine against this strain means that, from the outset, we lose ground as this variant spreads.  To be clear, not only is vaccination not rapidly increasing our collective immunity, instead, the lower efficacy of the vaccine means that we are, in effect, losing immunity.  That was the whole point of the charts in the second section above.

The way I see it, at this point, this time, whatever happens, happens.  Certainly no Republican states, and likely no states, are going to take action in the event that the Delta strain leads to a U.S. fifth wave.  So whatever is going to happen is going to happen.

Run that mix through the blender and my guess is that we’re going to have (some sort of) a fifth wave.  Not, as I initially expected, due to heavy use of air conditioning mid-summer, as was the case for the U.S. second wave.  But because we’re facing yet another round of substantial increase in the infectiousness of COVID-19, and far from taking offsetting measures, we’ve all let our guards down and are vaccinating at a casual pace.

On the plus side, at some point, the virus runs out of bodies.   We now have a fairly large chunk of the population that is immune.  So this can’t possibly be as bad as the U.S. third wave.   But my bet is, this pandemic isn’t over yet.   Just as it is not yet over in Great Britain.

Post #1159: Robinson estate sidewalks


In this post, I’m just trying to get my bookkeeping straight on the Robinson estate  sidewalks in the Town of Vienna, VA. This will be of no interest to anyone outside of Vienna, and of questionable interest to those who live here.

I think we just saw the first one of those completed, on Pleasant Street.  And if that’s true, that’s worth noting.

But before I can say that, I need to get my head straight about where this now stands.  The following is a timeline for this process, centering around my prior posts on this issue.

April, 2019, starting the clock.  I believe this is when information of the Robinson bequest was formally delivered to the Town of Vienna, so this is the date when clock starts for the five-year period in which the Town must spend the money.

Post #518, the 1/18/2020 meeting of the Transportation Safety Committee.  This is where first learned of the Robinson bequest for the construction of sidewalks in Vienna, and the restrictions on the use of the money.  Apparently this discussion took place almost a full year after the bequest was made and the clock begain ticking on the five-year period in which the Town must use the money.

Post #532, the 2/24/2020 Town Council meeting.  This is the meeting where Town Council authorized sidewalks on three streets literally chosen by the executor of the Robinson estate.  This is also the first time that Town Council clearly stated that the estate’s executor would literally only pay for the sidewalk (not curb and gutter).  This was also the first time that I calculated what a ludicrously small fraction of the Robinson estate money could be spent under the rules imposed by the estate’s executor.

The meeting materials for that meeting listed five candidates, of which Town Council approved three (in boldface below).  I vaguely recall that the other two were rejected by residents on those streets but I may be imagining that.

* Even side of DeSale Street SW from Moore Street to Tapawingo Road
* Odd side of DeSale Street SW from Tapawingo Road to end
* Even side of Holmes Drive NW from John Marshall Drive to Upham Place
* Odd side of Cabin Road SE from Branch Road to Glyndon Street
* Even side of Plum Street SW from Cottage Street to Tapawingo Road

Post #1056, March 14, 20201, I revisited Plum Street (above), more than year after the Town appeared to approve a sidewalk there.  I had something of a senior moment based on the complete and total absence of a sidewalk.  Near as I can recall, the Town had done nothing about spending the Robinson sidewalk money since that 2/24/2020 meeting, but I can’t claim to have been tracking that closely.  For sure, there was no sidewalk on Plum, nor on Cabin, so if they’d been working on it, they were taking their time.  Particularly given the five-year limit on spending the Robinson funds.

By April 5, 2021, the Town had a new list of sidewalks to be considered, but it included some pretty bad candidates.  That’s the gist of Post #1096.  My guess is that with the restrictions imposed by the executor of the Robinson estate, the Town was scraping the bottom of the barrel trying to find candidates for sidewalks.  At that point, one Town Council candidate (David Patariu) openly suggested that the Town take the Robinson estate to court to clarify that the actual language of the will did not contain those restrictions, and to get the court to remove those restrictions so that the Town could build sidewalks where they were needed, not where curb and gutter happened to have been put into place decades ago.

By April 23, 2021, the Town clearly had a list of 11 proposed projects that, in theory, constituted the Town’s proposed plan for spending the Robinson sidewalk money.  They were going to have a public hearing on those the following Monday (4/26/2021), and by report, that public hearing did not go well.  In Post #1120, I again took the time to show how little of the available money this was likely to use.  I have since been told that my costs — based on VDOT data — are too low.  To which my response is, then double my estimate, it’ll still be a tiny fraction of the total available funds.

In Post #1133 (May 3, 2021), I talked about the five projects that the Town approved after that 4/26/2021 public hearing and Town Council meeting.  At this point, there appear to be no rules whatsoever as to what can and cannot be built using the Robinson estate money.  Some streets have curb and gutter, others don’t, some are fill-in sections, some are entirely new street segments to have sidewalk, and so on.  If there is some rule behind any of that, I was not apparent to me.

And, this was not some sort of make-believe.  The Town’s meeting materials had contractors and firm contract prices listed.  So approval of those seemed to indicate a pretty solid intent to build that hodgepodge of sidewalk sections.

Do I even need to say this?  Again, any plausible total spending for the five approved projects would be dwarfed by the overall size of the Robinson bequest, which by this time had grown to a reported $9M.

Those five projects, approved in the 4/26/2021 Town Council meeting, are the focus on the rest of this post.  To cut to the chase, I thought that all five of those contracts were superseded by what happened next.  But in fact, one of the five projects was built.  The other four were either canceled, or waiting.

Finally (Post #1139), at a Town Council work session scheduled for 5/10/2021, the Town had a brand-new, much larger list of sidewalk candidates.  This, along with a brand new story as to what could and could not be done with Robinson estate money (curb and gutter?  who said anything about curb and gutter)?  This now included a thorough rewriting of history, as if this had been the plan all along, along with a document that listed a new, much-higher cost for a project that had already had contract bids, along with an astounding $450 per foot average cost estimate for the construction of plain-vanilla sidewalks in Vienna.

But, by gum, the Town finally had a document — no matter its oddities — by which it could claim that it had a plan for spending the Robinson estate sidewalk funds.  I think that, with the $450/foot, the new higher costs listed for already-bid project, and the inclusion of all the roads that they thought fit (including some clearly bad candidates, see Post #1096), they were able to claim with a straight face that they had more than $10M worth of potential sidewalk projects.  And thus had a plan that would, on paper at least, spend that money.

Yeah.  OK.  Sure.  That’s good, I guess.

Five projects.

Now that I’m back up to speed, my sole goal for this post is to see what the Town actually has done for the five projects that it appeared to approve on 4/26/2021.  Because, near as I can recall, one of those re-appeared in the final plan at a vastly different cost, and the other four just disappeared entirely, and are not listed at all in the master plan for the use of the Robinson sidewalk funds.

And so, after all that to-ing and fro-ing, two years and two months into the five-year period during which that money must be spent, I just want a straight answer to a simple question:  Have they started working on those five projects or haven’t they? 

And as I now have come to realize is the norm for this topic, the answer is far stranger than I would have guessed.

The list of five projects is laid out in Post #1133.  I rode past all five of them this afternoon, and the status is:

124 Courthouse Road SW.  Not started. The missing sidewalk is actually along the back of the property, where Cottage Street dead-ends at the shopping center.  It’s about 100′ of sidewalk.

503 Ware Street SW (~$17K).  Not started. This is right across from Meadow Lane park.  This is also about 100′ of sidewalk


1002 Hillcrest Drive SW (~$22K).  Not started. This is about a 200′ long stretch.



Cabin Road SE – Branch Road to Glyndon Street.  Not started.  The entire stretch is just over 800′ long and pretty much dead flat.


Pleasant Street SW – Courthouse Road to Maple Avenue.  Finished and road repaved.  This is a several-hundred-foot stretch of road with sidewalk on one side, and no sidewalk on the other.


Here’s a before and after of Pleasant Street, courtesy of Google Street view and some photos taken today:


Source:  Google Street View.



By eye, and by feel, it seems as if the Town widened the road a bit as it put in the sidewalk, but objectively, near as I can tell, that’s not true to any material degree.  It’s just a lot easier to drive at the edge of the road when there actually is a well-defined edge (curb), instead of just pavement that stops.

At any rate, I find the outcome here quite odd.  Three of those projects are no longer listed anywhere, and there’s no evidence of sidewalk construction.  One of them — Pine — remains listed in the Town’s current plan, but now at a much higher price than the actual bid.  And one of them — Pleasant — no longer remains listed as a Robinson estate project, but is now completely done, six weeks after the Town approved it.  This, in a Town where it was reputed to take two years to get a sidewalk done.

In any case, I think I count this as the first sidewalk completed from the Robinson estate funds.  I don’t think it would be asking too much for the Town to put up a little marker or something to commemorate.  People get their names on a little plaque when they donate the cost of a bench to one of the local parks.  Seems like every one of these new sidewalks ought to have something similar.

Maybe just a stamp, C&MR, to be stamped into the wet concrete at the completion of every project paid out of those funds.  Fifty years from now, people might notice that and wonder what it’s all about.  Maybe somebody will bother to look it up.  Or if you don’t like that simple approach, find some alternative.  The physical concrete in those sidewalks is no different from any other.  Seems like all the more reason to provide a permanent reminder of the gift behind it.  In any case, it seems a bit cold to finish a sidewalk, paid for from that bequest, and just move along to the next job.


Still, I keep wondering, why this street?  Why so fast?  Did they or didn’t they widen the road a bit as they did this?

This section of road met none of the criteria that were once presented as governing the use of those Robinson funds.  Most of the section where sidewalks were placed had no curb or gutter.  And this street already has sidewalk own the full length of it, on one side.  And so on.

But there it sits, right across the street from 44 new dwelling units shoehorned into roughly two acres, constructed under MAC zoning.  (I guess it’s rude to say “shoehorned” about townhouses that will cost more than my house.)

And so you might reasonably ask, is this just another part of the Town’s plan for the densification of Maple Avenue?  And that’s why this, uniquely among all potential projects, got priority?  Or was it the case that they needed to do it while the road paving crews were still here, owing to the nature of the roadway prior to the installation of sidewalks?  And so the proximity to Maple and MAC development is just a coincidence?

Or yet some other explanation of why this street, and why so promptly.

As a member of the peasantry, I’ll never know.  But in a Town where the standard spiel is that sidewalks take at best a couple of years, this one, completed about six weeks from the time the Town Council authorized it, certainly stands out.  I just wish I understood why.

Post #1158: High-volume knee replacement surgeons in DC, MD, VA


If you’re thinking of having knee replacement surgery and live in DC, MD, or VA, you may want to download and have a look at this Excel (.xlsx) file:

High volume knee replacement surgeons DC-MD-VA
Size: 0,2 MB


The workbook linked above contains a list of orthopedic surgeons in DC, MD, or VA who performed knee replacements on traditional Medicare enrollees in 2018.  It shows the volume of each surgeon’s Medicare-paid total knee replacements, partial replacements, and repairs (revisions) of replacements. A second sheet in the workbook provides counts of fee-for-service Medicare inpatient knee and hip replacements by hospital for the same three states.

Why should you care about how many knee replacements a surgeon has done?  In a phrase, practice makes perfect.  This is true of most complex surgical procedures such as joint replacements, and is particularly true of partial knee replacements.  To quote one carefully-done large scale study out of Great Britain:

Caseload had a profound effect on implant survival. Low-volume surgeons had a high revision rate ... and therefore should consider either stopping or doing more UKR procedures. High-volume surgeons ... demonstrated a 10-year survival rate of 97.5%, which was similar to that reported in registries for the best-performing TKRs.

(N.B., UKR = partial knee replacement, TKR = total knee replacement, revision = repair or replacement).

Why care about Medicare-paid surgeries?  Mainly, that’s the only data you can get that shows the number of procedures performed by individual surgeons.  The data and methods are public information (accessible at this link).  That raw information is impossible for most people to use, so I created the workbook above.  As importantly, Medicare is a big piece of this market.  In these three states, in 2018, the traditional (fee-for-service) Medicare program paid for roughly half of all knee replacement surgeries (documented below).  And so, while this Medicare-based workbook only shows part of each physician’s practice, in most cases it shows a large part of it.

Think of this as a place to start as you decide upon a surgeon and hospital for your knee replacement.  Volume of surgery alone is not a direct measure of a physician’s quality or competence.  But if you’re going to have a knee joint replaced, you probably want a surgeon who replaces a lot of them.   You’ll obviously want to look at more than just surgical volume before choosing a surgeon.  But surgical volume is one reasonable criterion.  This is one of the few places were you can find orthopedic surgeons known to do a high volume of knee replacement surgery.

For now, you only need to know a few things to use the data. 

  • There are no warranties or guaranties about the accuracy of this information.  Use it at your own risk.
  • This is a snapshot of 2018.  Things change, people move around.
  • These are based on claims (bills) submitted by these surgeons and paid by Medicare.  There may be occasional errors, such as the inclusion of a mix of surgery and assistant-at-surgery services for an individual surgeon.
  • This is restricted to self-designated orthopedic surgeons.  This may omit the occasional legitimate knee surgeon who (e.g.) self-designates as a sports medicine physician or other sub-specialty.
  • An orthopedic surgeon had to be paid for at least eleven knee surgeries of a given type in order to be listed.  (A “type” in this case is an AMA Current Procedural Terminology (r) code.)  A blank entry in this file should best be interpreted as “fewer than eleven surgeries”.
  • An orthopedic surgeon practicing in this geographic area might have been correctly omitted from this file because a) they moved here after 2018, or b) the address of their main practice is listed as being in some other state, or c) they did fewer than eleven of every type of knee surgery on traditional Medicare enrollees in 2018.

This workbook also contains a crude ZIP-code based distance measure.  You can use a standard Excel method (“filtering”) to find orthopedic surgeons near you.  For example, you can easily reduce the list to orthopedic surgeons within 30 miles of a given ZIP code, who did at least 100 Medicare-paid knee replacements in 2018.  The README sheet in the workbook briefly explains how to filter the data.

Absolutely nothing about this file is perfect.  The counts are incomplete, the distance measure is crude, and so on.  But for most users, it’s probably good enough to be useful.   If you’ve ever tried to find a specialist, used an on-line website, and been faced with a list of hundreds of names, you’ll understand the utility of having some systematic approach to whittling down the choices.  At the very least, if you’ve gotten recommendations for a surgeon, you can now look them up and see whether or not they appear to do a lot of knee replacements.  And, as discussed below, you can often use the Medicare Compare website to identify hospitals to which that surgeon admits patients.

The rest of this post talks a bit more about the underlying data source, documents the estimate of traditional Medicare’s share of the market in these three states, and rambles a bit about about why I put this together.


The data, and fee-for-service Medicare’s share of the local knee replacement market.

The Excel workbook above is based on Medicare claims (medical bill) data.  In this section, I describe the relevant parts of the Medicare program, and show that for the three states in question (DC, MD, VA), in total, traditional fee-for-service Medicare paid for about half of all knee replacements in 2018.  Throughout, I ignore Medicare Part D (drug) coverage.

Roughly 60 million Americans are insured via Medicare, our federal health insurance for the aged and disabled. You can find a concise summary of enrollment statistics at this link.

Of those, just over one-third are actually enrolled in private health care plans, termed “Medicare Advantage” or “Medicare Part C” plans.  For those beneficiaries, Medicare simply pays monthly premiums to those plans, just like any other health insurance coverage.  With limited exceptions, the Medicare program itself never sees bills (claims) for services provided to those individuals.  They are (almost by definition) excluded from the counts in the Excel workbook provided here.

Roughly two-thirds remain in the traditional “fee-for-service” Medicare program.  For those individuals, Medicare hires contractors to process and pay their covered health care bills.  For those individuals, the Medicare program gets an electronic copy of every bill that was paid.  One way or the other, each bill shows what service was provided, and how much Medicare paid for it. Those are the counts that make up the data for the workbook above.

There is a small factor that also must be considered, which is that Medicare covers inpatient facility care (Part A) separately from payment for professional and outpatient services, such as payment to a surgeon (Part B).   An increasingly large share of enrollees in traditional Medicare have Part A coverage (which is free) but not Part B coverage (which is merely heavily subsidized, not completely free).  (This does not happen in Medicare Advantage, because (with rare exception) you must have both Part A and Part B coverage to be able to enroll in a Medicare Advantage plan.) Working from these enrollment statistics, about five million Medicare beneficiaries have Part A but not Part B.  Because these are by definition concentrated solely in the fee-for-service portion of Medicare, this means that currently about 12.5 percent of Medicare fee-for-service beneficiaries have Part A (hospital inpatient bill) coverage, but not Part B (surgeon’s bills) coverage.  These individuals tend to be relatively low users of care.  But to the extent that such an individual would get an inpatient knee replacement, Medicare would see a bill from the hospital, but not from the surgeon.

For the U.S. as a whole, we can use a reference inpatient database (the AHRQ HCUP database) to estimate the fraction of all inpatient knee replacements paid by any part of Medicare.  This will include both traditional fee-for-service Medicare and Medicare Advantage plans.  As of 2018, Medicare paid for 57% of all inpatient knee replacements.

But that would include not only traditional Medicare, but Medicare Advantage as well.  To parse those apart, I relied on an old analysis that I had done for clients back when I worked in this area.  (That analysis required separating out Medicare fee-for-service discharges from records for Medicare Advantage discharges.)  Based on that analysis, for knee surgery, for DC+MD+VA combined, traditional Medicare accounted for 90 percent of inpatient knee replacements in 2017.  (For the U.S. as a whole, it was more like 70%).

So fee-for-service (traditional) Medicare’s share of inpatient knee replacements, for DC+MD+VA, would amount to 90% of 57%, or 51%.

Finally, I have to guess what fraction of those with Medicare fee-for-service inpatient knee replacement had Part A but not Part B.  This is a lot harder, because those without Part B tend to have a much lower rate of service use for elective surgery such as knee replacement.  As a reasonable guess, based on years of looking at this question for other procedures, I’d guess that 6 percent of those knee replacement patients had Part A but not Part B.

So fee-for-service (traditional) Medicare’s share of surgeon’s bills, for knee replacements, for DC+MD+VA, would amount to 94% of 51%, or 48%.

The upshot of all of that is that, if I’m looking at fee-for-service knee replacement claims paid by Medicare Part B, in DC+MD+VA, in 2018, I’m looking at just under half of all knee replacements done in this geographic area.

The actual public-use data file is Medicare’s summary of the individual claims (bills).  Medicare summarized the file by physician identifier, place of service (inpatient or outpatient), and procedure (AMA Common Procedural Terminology (r) Code).  As a privacy protection measure, Medicare blanks the data any time that leads to a count of fewer than 11 total services.

Because of that summary-and-redaction process, I will lose some counts of knee replacements every time a surgeon does fewer than 11 of any one particular type of knee surgery.  But that factor is more-or-less irrelevant if the task is to find high-volume surgeons.  It might might drop a lot of volume out of the file in total, but it should leave the counts for high-volume surgeons more-or-less unaffected.

I did considerable post-processing of the Medicare file, to achieve two things.  First, I edited out aberrant-looking lines, mostly trying to get rid of claims for assistance-at-surgery.  (Assistance-at-surgery is exactly what it sounds like — it’s the service of assisting the main surgeon who performs the surgery.  Unfortunately, assistance-at-surgery is billed using the same codes as the surgery itself, with a separate “modifier” indicating assistance.  Medicare just summarizes all the bills, regardless of modifier.)  Second, I added the counts for the range of surgical codes to generate the categories you see labeled on the spreadsheet.

As a validation, I found that after all my edits, and all the CMS redactions of cells with fewer than 11 surgeries, I ended up with 93% of the “benchmark” count of U.S. total knee replacements.  (The benchmark is based on the Medicare Part B National Summary file, excluding assistance-at-surgery (80s) claims.)

Why did I put this together.

I worked more than 30 years as a health economist, and spent most of that time analyzing Medicare claims data.  That was not quite as hellishly boring as it sounds.  More to the point, after three decades, I was both good and quick at doing that sort of analysis.

During my career, I was repeated floored by how hard it was for the lay person to get an answer to even the simplest questions about health care, based on Medicare’s experience.  If somebody in the Medicare program had not tabulated exactly what you wanted, just by chance, then you were out of luck.  In most cases, for most questions, my sole option was to work up an analysis, from scratch, directly from the large public-use or limited versions of the Medicare claims and enrollment data files.

Absent that data access and analytical firepower, I could not get answers to obvious and simple questions.  And it wasn’t so much that Medicare didn’t occasionally try to provide summary data that could answer some questions.  It’s more that most questions you’d like to see answered require just a little bit of analysis that is specific to that question.

And so it is with these counts of surgeries.  Medicare makes the raw summary file available, and even has an interactive on-line query system.  And even with that, I’d bet that the average American would find it impossible to use that system to produce any sort of meaningful information.  You have to know just a little bit — about the codes used to represent the surgeries, about assistance-at-surgery claims — to convert the raw data to a useful listing.

And, since I spent 30 years developing those skills, I figured I should put them to some use.

This is actually the second time I’ve done this analysis.  The first time was years ago, when a friend’s wife was facing a replacement of a failing partial (unicoldylar) knee.  Her knee was not done correctly the first time, it had worn prematurely, and replacements are much harder than initial implants.  She really wanted to find the best of the best for her surgery.  And so I did essentially this analysis, and in fact came across the surgeon who literally wrote the textbook on revisions of uni knees.

That story then had a happy ending.  But without access to information like this, it’s hard to pick a surgeon.  You are reduced to asking friends for suggestions, or soliciting suggestions from social media.  Both of which can work, but neither of which is very systematic.

The second time I did this analysis was two weeks ago, when a question about surgery for a uni knee revision was posted on NextDoor.  I figured, I might as well dust off the old analysis and see what it said now.  And it actually turned up the same national expert on uni knees, at the top of the listing.

Otherwise, finding and choosing a surgery is just a hard task.  You scrape together whatever information you can find from various sources.  Maybe you solicit recommendations from your family physician, friends, or via social media.  And you try to synthesize all of that.

What I have found is that on-line physician finder sites give you an overwhelming number of choices.  And when it comes to surgeons, it seems like all of them get top ratings.  They are great for showing you all of your options.  They are not much good when it comes to narrowing your options.

And that’s why I like practice-makes-perfect as a guide.  It’s not merely that you should avoid surgeons with low volumes of the particular surgery you need.  It’s that you will find that, particularly with anything out-of-the-ordinary, surgeons with high volumes got that way because they had a reputation for being the local expert.  A surgeon doesn’t get to do (say) 80 partial knee revisions per year unless that surgeon has the reputation as the go-to person for that particular surgery.

So there you have it.  It’s not perfect, slick, or pretty, but it makes that Medicare data available to people who might want to use it.  Now that I’ve worked out the kinks for doing this from public-use data, there’s no barrier to doing a national version of this file, and there are only small barriers to doing this for other common surgeries where the practice-makes-perfect effect is known to be important.  As a final note, Medicare updates the underlying data annually in November, so if I’m still in this business at that time, I should be able to update this using newer data then.

Post #G21-032: Cucumber beetles, bee-proof sticky traps, neem oil.

This post follows on a series of posts regarding cucumber beetles.  You can read the background in Post #G21-027.

(Source for photo:  University of Kentucky).


This year, I have a plan of sorts for dealing with cucumber beetles.

First, I continue to do what I did last year.  I go into the garden every morning and kill the cucumber beetles that are chowing down inside my squash blossoms.

That’s more of a vendetta than an actual plan.  Satisfying but ineffective.  I need something more systematic.

The typical recommendation for dealing with cucumber beetles is to use some sort of non-specific contact poison.  That would include Sevin (carbaryl), pyrethrin (short-lived natural compound), or permethrin (longer-lived synthetic pyrethrin analogs).

I’m not going to do that.  The main problem I have with that approach is that those substances kill more-or-less all insects that come into contact with them.  Secondarily, the short-lived ones are a lot of work, and the long-lived ones leave residues.  If I want pesticide residues in my vegetables I’ll buy them from the grocery store.

Last year I tried a pheremone-based lure and sticky trap, and I’m not going to try that again.  At least not in that raw format.  Those traps did attract cucumber beetles.  And they caught every other manner of insect as well.   They were far too non-specific for use in a small home garden.

That seemed to leave me with four plausible options.  These either attack the beetles with physical means, or rely on relatively short-lived toxins that have to be eaten by the insect in order to poison it.  These short-lived toxins have a reputation for being bee-safe when used correctly.

These options were:

  • Yellow sticky traps screened to prevent larger insects from reaching them.
  • Possibly, diatomaceous earth sprinkled on the leaves.
  • Possibly, insecticidal neem oil solution applies to the leaves of the cucumber plants.
  • Possibly, high-strength spinosad solution applied to the leaves of the cucumber plants.

I’m working through those, and I’ve come up with these additional ones:

  • Peppermint-garlic spray, to make the cucurbits harder to find.
  • Re-think the bee-proof trap using pheremone-based sticky traps or other types of traps, screened to prevent larger insects from reaching them.
  • Plant cucumbers that are resistant to bacterial wilt.

The rest of this post described what I’ve tried and not yet tried, and how that has worked out so far.

1:  The mythical cucumber beetle season and a strategy of timing your plantings.

I summarized what I could find out about cucumber beetle season and life cycle in Post #G21-030Here in Zone 7, from the gardener’s perspective, there should be three generations of beetles.  The first consists last year’s adults that  overwintered nearby.  Those beetles arrive around the end of May.  The subsequent two generations are the children and grandchildren of those adults, and should show up June/July and September/October.

But guess what?  I don’t think I’m seeing any clear and obvious end point of one generation and starting point for the next.  What I see, in my morning routine of inspecting the squash blossoms, is day after day where some beetles are present.

What I’m not seeing is any prolonged absence of cucumber beetles.  No beetle-free period between the three generations.  So while there may technically be three generations (one overwintered, and two new ones) in a typical year, I’m afraid that what I’m actually going to see is one summer-long cucumber beetle season.

My problem is that any number greater than zero is too many.  It’s not the physical damage to the plants that is the problem.  It’s that these beetles spread bacterial wilt, and that’s what killed off my cucumber crop last year.  All it takes is one feeding, by one infected beetle, and I’ll lose a cucumber plant.

This makes a hash of any strategy based on the timing of my plantings to avoid cucumber beetles.  A strategy mentioned by both Virginia Tech and University of Maryland was to plant cucumbers mid-June in order to avoid cucumber beetles.  But if I’m going to have cucumber beetles in my garden for the entire summer, my cucumbers will always be at risk of being killed by bacterial wilt.  The only solution would be to tear up what I’ve planted and re-plant with cucumbers that are highly resistant to bacterial wilt.


2:  Bee-proof sticky traps:  Total failure so far.

The construction of these is detailed in Post #G21-029.  The idea is to use a standard yellow sticky trap, but surround it with 1/8″ mesh hardware cloth to exclude bees and butterflies.

Ten of those have now been in my garden for more than a week.  I think I can confidently declare them to be a total failure for catching cucumber beetles.  I definitely still have striped and spotted cucumber beetles in my garden.  But none on my sticky traps.

On the plus side, these didn’t catch any bees, butterflies or other obvious beneficial insects.

I’m not sure why these failed.  Possibly the screening dulls the yellow color and prevents them from attracting beetles.  Possibly they need some sort of floral lure to be able to compete with the real flowers.  Possibly the cucumber beetles just won’t go through that mesh.

The verdict is that this particular setup is a failure.  That doesn’t rule out alternatives, so I will keep experimenting with these.

  • Spray-painting the screens bright yellow is quick and cheap.
  • I could try yellow bowls of soapy water with cucurbit flowers in them, covered with mesh.  That’s also quick and cheap.
  • I could buy pheremone-based sticky traps and surround those with mesh.

I’m not giving up on the concept quite yet.  But it’s clear that the combination of off-the-shelf sticky trap and mesh does not yield a functioning cucumber beetle trap.

3:  Plant varieties resistant to bacterial wilt.

I finally gave in and bought two cucumber varieties that are advertised as being highly resistant to bacterial wilt.  Those are Little Leaf and Cross Country (presumably a cross with Country Fair, another resistant variety).  I planted those in a couple of places in my garden yesterday.  We’ll see if they survive or possibly even thrive.

As a bonus, the Little Leaf cucumbers are parthenocarpic (require no pollination).  If worst comes to worst, I can grow those entirely under insect-excluding row cover.

4:  Neem:  I tried it, but I may never know if it works or not.

I have seen two common short-lived organic pesticides been mentioned for potential beetle control: Neem and spinosad.  Neither one of these is supposed to be very effective at controlling cucumber beetles.

Here are the reasons I chose to spray with neem.

First, at least one commercial supplier of cucumber seeds suggests using azidarachtin to control cucumber beetles.  That’s the insecticide in neem oil.

Second, it’s not clear that anecdotal reports of neem’s inability to control adult cucumber beetles are based on the form of neem oil that actually contains insecticide.

There are two distinct forms in which you can purchase “neem oil”.  One contains insecticide, one does not.

One form is the hydrophobic extract.  That is more-or-less vegetable oil containing only trace amounts of actual insecticides.  This product, for example, from Bonide, is just a neem-based horticultural oil.  The other is the complete or raw or pure neem oil.  That form contains a potent insecticide, azidarachtinThis product, for example, advertises its high azidarachtin content.

People seldom distinguish between these two forms of neem when they report the results of “using neem oil” to control pests.  Accordingly, when some gardeners report poor results using neem to control cucumber beetles, you don’t really know what that means.  There’s a good chance they used the more-commonly-available hydrophobic extract (the pesticide-free version), instead of raw neem oil (the pesticide-containing version).  As a result, it’s possible that raw neem oil actually does work on cucumber beetles, despite internet reports that “neem oil” does not work well.

Third, neem oil (in either form) works well to smother and kill insect eggs.  This is why I sprayed around the bases of all my cucurbits.  By reputation, that’s where the female cucumber beetles go to lay their eggs, providing the larvae with access to the cucurbit roots that they will feed on.

Fourth, raw neem oil has a reputation for being able to kill larvae in the soil when used as a soil drench.  I’m not going to do that — I’m not going to saturate the soil around my plants with neem solution — but to the extent that the eggs hatch in the presence of raw neem oil, there’s some chance it will kill the emerging larvae.

Practically speaking, there’s no good way to tell whether or not this worked.  I simply don’t know enough about what cucumber beetle numbers to expect in the absence of neem.  I don’t have a big enough garden area even to think about test and control plots.

So this is more-or-less an act of faith.  It’s also reasonably safe, cheap, and quick to do.  Ultimately, this falls under “might as well give it a try”, rather than “let me test this formally and see if it works”.

5:  Diatomaceous Earth:  Too clumsy.

And by that I mean, I’m too clumsy.  Or, at least, I’m too clumsy to apply that stuff with a blower or a shaker.  I gave it a try, but no matter how I apply it, some parts of some leaves get absolutely plastered with the stuff, other parts are bare.  And once they’re plastered, presumably there’s not a lot of photosynthesis going on.

Plausibly, I could find a better way to apply it.  I’ve heard of people mixing it with water and spraying it on.

In any case, it’s a non-specific contact poison that has to be re-applied after every rain.  I tried it on my most beaten-up cucumber.  There’s no way to know if it works.  I might give it a more serious try if nothing else works.  But for now, this is going back on the shelf.

I think the same goes for Surround (r) kaolin clay.  While that has the reputation for deterring cucumber beetles, it has to be re-applied after every rain.  And I suspect that it must reduce photosynthesis because it surely blocks some portion of the sunlight hitting the leaf.  I’ll try that if nothing else works.


6:  Mint and garlic spray, I may try this.

The theory here is that this disguises the smell of your curubits and makes it harder for the cucumber beetle to find them.  Given that we have a lot of mint growing in our yard, this one certainly seems easy enough to try.  Grind up some mint and garlic, let it steep in water for a day or so, and spray the resulting water on your plants.

I’m not betting on this one.  The wily cucumber beetle has managed to avoid everything I’ve thrown at it so far.  I’d be surprised if it would be taken in by a little bit of mint and garlic smell on top of the smell of cucurbits

I’m keeping this one on the list in case nothing else works.  Its harmless and cheap.

Post #1157: COVID-19 trend to 6/10/2021, disappearing data and the end of the U.S. fourth wave.

Data dropouts

Well, this had to happen sooner or later.  More states are reporting less data, less frequently, regarding COVID-19.  You can read the full writeup at this link.

This less-than-daily report is not a completely new phenomenon.  It has always been true that some states — typically low-population rural states — did not report data on Sundays.  This added a harmless little “flat spot” in their seven-day-moving average curves, but did not meaningfully distort the overall picture.

But now Florida (of course, Florida) has decided to report information just once a week.  With some lag, as well.  This is the only state where the new-cases data are now, in effect, missing for an entire week at a time, driving the seven-day moving average down to zero on a real-time basis.  That began June 4.   And that puts a serious kink in any sort of data analysis.

Across the states, the data reporting situation is summarized in the table below.    Out of 51 states (including DC), about half continue to report every day.  Those tend to be the larger states, and they contain about 69% of the population.  The rest of the states skip reporting one or more days per week.  For those states, the daily new case count will show as zero for those days, followed by some larger number as multiple days’ worth of cases are reported on the next reporting day.

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 6/11/2021, from”  The NY Times U.S. tracking page may be found at

For most of these states, the non-reporting remains a minor issue.  One or two days per week, their time-series will show a flat spot.  This will be followed by a jump as the time series corrects back to the true underlying level of new cases.  A trend line that ends on (say) a Thursday (such as today’s analysis) will show all those states at their true levels.

But Florida is a special case.  I can either drop it, or gap-fill it by using the prior week’s new-case rate as the gap-fill, until new data appear again.  When all is said and done, it’s probably smarter just to drop Florida, for now, at least.

These changes, along with ongoing reporting issues in (e.g.) Texas and elsewhere, make it hard to say much about ongoing trends.

A leveling-off off of the new cases curve

With the data reporting caveats in mind, as far as I can tell, this past week, the downward trend of the U.S. COVID-19 fourth wave appears to have stopped.  In my last look at trends, I overstated the downward trend due to missing data from Florida.  But when I now drop Florida, and add the last few days’ worth of data, the new-cases curve appears to have flattened.

That may slightly overstate the flattening of the curve, due to some data reporting issues in Texas.  (Texas added then removed a considerable number of old cases to their data last week, but without enough information to allow me to correct the time-series.)

If I divide the states by (my estimate of) the fraction of the population already immune to COVID-19, it seems fairly clear that this is not merely the consequence of bad data reporting in a few states.  There’s still a slight downward trend in the states with the highest levels of immunity (black line), but a complete leveling-off in states with the lowest levels of immunity.


Why has the downward trend in case cases now flattened out?

There has been a lot of talk about the new Delta variant of COVID-19 (formerly the Indian variant, still identifiable as B.1.617.2, now simply termed “Delta”).  But that’s still far too infrequent in the U.S. to have any material impact.  As of now, it accounts for about 6% of new cases.

Source:  CDC COVID-19 data tracker.

There are plenty of reasons to worry about this for the near future.

    • It’s about 40% more transmissible (infectious) than the British variant that is now the dominant strain in the U.S.
    • It causes much worse symptoms, particularly among younger people.
    • The current vaccines are not as effective against it as they are against other strains.

You can read all that good news by clicking the link to this WebMD article.  But, again, it’s not prevalent enough yet in the U.S. to be causing a flattening of the curve.

Seasonality is always a good guess.  COVID-19 appears to have a strong seasonality to it.  As we made the transition from winter to summer, disease transmission fell — just as it would for influenza, say.  But now were in summer, and should expect no more seasonality-related declines.

Memorial Day weekend is not really a plausible suspect for this leveling-off of new cases.  The main reason is that, despite the hype, there never was any post-holiday “surge” in the U.S., for any prior holidays (e.g., Post #922, Post #1029).  Given that, it’s hard to believe that, uniquely, there would be one for Memorial Day, when most social activities are in safe outdoor locations anyway.  The only thing that makes this even remotely plausible is the timing.  Infections acquired at the start of Memorial Day weekend would start showing up in the data at the end of this current week.  (June 9 is 12 days from the Saturday of Memorial Day weekend.  That 12-day figure is my best estimate for the typical lag between infection and reporting in the U.S.)

If I had to pick a cause, I’d say seasonality.  Part of the decline in new cases, after the peak of the U.S. fourth wave, was due to vaccination.  And part was just ongoing seasonal trend.  New vaccinations have slowed to a crawl.   And we’re now fully into summer, and should expect no more help from seasonality this year.  Absent those two drivers, it seems reasonable that the decline in cases would cease.

That said, it’s only been a week now.  It’s too soon to make any firm conclusions.  And the picture is muddled by data reporting issues from the Memorial Day holiday, and by changes in data reporting by the states.  Give it another week and it should be clear whether or not the U.S. fourth wave has ended.


Post #1156: COVID-19 trends to 6/7/2021: It’s just a data reporting glitch

I’ve analyzed enough health care data to know that this can’t be a real increase in cases.  It has to be a data reporting glitch.  I just have to work out what it is.

Here’s the answer:  This is a result of the Memorial Day.  And it will disappear tomorrow.  The reason is that today’s seven-day moving average actually has eight days’ worth of cases it in, for states that didn’t report data on Memorial Day.

A simple spreadsheet illustrates what’s happening.  Here I’ve represented a day’s worth of new cases with a “1”.  A lot of states didn’t report new cases on Memorial day, but instead reported two days’ worth of cases the next day.  With that reporting pattern, you’ll see a dip in the seven-day moving average reported on Memorial day, and an offsetting jump in the seven-day moving average seven days later.


Post #1155: Architect hired for Patrick Henry Parking Garage and Library

I’ve been avoiding writing about the Town of Vienna of late.  The Town government is in the process of rewriting all the zoning laws, during the pandemic.  There’s no doubt that we’re going to get zoned for a lot more density.  It’s just a question of how dense the Town is going to be.

I’m about a month behind in terms of keeping track of what’s going on with the rezoning.  After the Town got its “economic development” report (Post #1138), I’ve been afraid to look at what’s been happening.

As a way of avoiding that for yet another day, let me get back to writing about the Town of Vienna by talking about the Patrick Henry Parking Garage (and Library).

Some actual news

Fairfax County has chosen the architect for the design and construction of the Patrick Henry Library and Parking Garage. Continue reading Post #1155: Architect hired for Patrick Henry Parking Garage and Library