Post #1045: Update on the U.K. variant B.1.1.7 in the US

To understand the methods here, look for prior posts using the Helix corporation data to track the U.K. coronavirus variant.

This information is updated weekly by the Helix Corporation.  Data sourced from the Helix® COVID-19 Surveillance Dashboard. Accessed at on 3/5/2021.

Briefly:  By their data, B.1.1.7 now accounts for 42% of Florida COVID-19 cases (42.49% as of 3/3/2021) and 27% of U.S. cases (27.03% as of 3/4/2021), per their Daily Percent SGTF of Positive Samples table. Continue reading Post #1045: Update on the U.K. variant B.1.1.7 in the US

Post #1044: A little statistical evidence that vaccination is working in Virginia

Let me show you something that has a positive message, for a change.

As of today (3/5/2021), Virginia has fully vaccinated 30% of the oldest old (80+), and has fully or partially vaccinated more than 50% of the oldest old.

By the time you’ve got half of a population vaccinated, you ought to be able to see the impact of that on the infection rate.  And, in fact, you can.

As this post demonstrates. Continue reading Post #1044: A little statistical evidence that vaccination is working in Virginia

Post #1043, Trend continues to improve

  • New COVID-19 cases are now down 75% from the early January peak.
  • Four out of five states showed declines in new cases yesterday.
  • The Northeast seems to have stabilized. All other regions show declining rates of new cases per day.
  • Florida still shows no apparent effects from the proliferation of the U.K. COVID-19 variant.

Continue reading Post #1043, Trend continues to improve

Post #1041: Trend to 3/3/2021, and the curious case of the British lockdown.

The US fell slightly below 20 new COVID-19 cases per 100,000 persons per day.

Otherwise, there is no material change from yesterday.  The majority of states continue to see small day-to-day reductions in new cases.  The Northeast as a whole does not, due mainly to New York and New Jersey.  By contrast, large reductions in new case counts continue unabated in California.

If I were to start a new calculation, from the point at which Texas’ data reporting had recovered fully (2/27/2021), the results would look like the box in the first graph.  The Northeast is stalled, California is not, and all other regions fall in-between. Continue reading Post #1041: Trend to 3/3/2021, and the curious case of the British lockdown.

Post #1040: U.K. variant: The fuse remains lit. Keep your eyes on Florida.


Putting aside for a moment the New York COVID-19 variant (which people claim is more contagious, a seemingly plausible claim based on the new-case trend in New York state),

and ignoring the California COVID-19 variant (which ditto, but if so, it’s surely not affecting the new case trend there, as California has the largest rate of decline of new COVID-19 cases in the nation),

and just forgetting about the South African variant as not being common enough in the U.S. yet,

(and fill in other variants at will here, because you’ve got plenty to choose from),

The granddaddy of COVID-19 variant problems for the U.S. is the U.K. variant, B.1.1.7.  Continue reading Post #1040: U.K. variant: The fuse remains lit. Keep your eyes on Florida.

Post #1038: William and Mary COVID cases through 3/1/2021

As of yesterday, the total number of COVID-19 cases on the William and Mary campus this semester more-or-less matches what I would have expected, based the rate  in Virginia for young adults.  Like so:

This tells you that they’ve achieved that in terms of total cases, but this doesn’t show you when W&M got the rate of spread down.  To look at that, let me divide this up week-by-week and look at the weekly increase in cases.  Like this:

The first week with the entire student body back, they found a lot of new cases on campus.  (The first blue bar is much taller than the first orange bar.)  But after that first week, the rate of spread of COVID-19 has been lower on the W&M campus than it was for young adults in Virginia as a whole.  In fact, that situation has gotten progressively better.  By the 4th week, the rate of new cases on the W&M campus was less than half that of Virginia young adults as a whole.

If I had to guess, the first week looks the way it does because W&M tests for COVID at a vastly higher rate than Virginia does (Post #1032).  And it’s a fair bet that most of what was identified in that first week was cases that came onto the campus with the newly-arriving students, and not cases that were contracted while students were on the campus.

(How could there be any cases at all, since everybody had to pass their pre-move-in testing?  These are infections that would have occurred too late to be caught by the pre-move-in screeing, plus a non-negligible number of false negative on that pre-move-in screening test.  (Again, see Post #1032, or Post #859 to see the high false negative rate of COVID-19 PCR testing.)  If test samples were taken  an average of 7 days prior to move-in, you’d expect to have at least 10 days’ worth of new infections within the move-in population.  Most (but not all) of those would get picked up with the initial round of post-move-in testing.  It’s not all because the post-move-in testing would also have a non-negligible number of false negatives.)

The upshot is that the COVID-19 situation at W&M appears to have been under good control pretty much from Day One.  And, as was true last semester, I can make the case that my daughter is safer at William and Mary than she would have been at home.  Or, at least, safer than the average young adult in Virginia.