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

Posted on March 2, 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.