Tag: W&M

The Fall 2021 COVID-19 outbreak continues to wind down.

This table, with one line per week, corrects a small math error I made in the prior version, with one line per day.  Continue reading Post #1282: William and Mary weekly update

Source:  Calculated from William and Mary COVID-19 dashboard.

The only oddity is that the total cumulative positives fell today.  That can happen due to (e.g.) a prior clerical error (such as counting the same student twice, then discovering that.)  Happens all the time in the state-reported COVID-19 counts.  So there might really have been three new cases, plus correction of a long-standing clerical error.  It’s tough to say, but not a lot of difference either way.

It’s not clear that it’s worthwhile to continue to track this.  Students are 98% vaccinated.  New cases are nearly zero.  Guess I’ll watch it for another week or two.

I guess people may now going to start questioning the continuing mask requirements.  And that may not be unreasonable.

But I’m not questioning them.  To understand my position, consider reading my post on how vaccinations work (Post #1200).  It’s a little ham-handed, in response to an outbreak at a big festival in Massachusetts.  But the main message is right.  Everything that cuts down on exposure to COVID-19 viral particles counts toward keeping new cases down.

So, I’m vaccinated and I wear an N95 mask in public spaces.

We can reasonably infer from the current situation that the combined effect of high vaccination rate and good COVID-19 hygiene has all but suppressed COVID-19 in this population.  Both factors contribute.

We cannot infer that vaccination alone will do it.  We don’t have that evidence.  We literally cannot predict how the rate of COVID-19 spread would change if we removed the “COVID-19 hygiene” portion of the current setup.

It’s the same logic behind “if it ain’t broke, don’t fix it”.

In my non-W&M posts, I’ve said repeatedly that I think we’re going to have a winter wave of COVID this year.  Best guess, it’ll be at least as bad as last year, based on the tradeoff between the higher infectiousness of the Delta variant, and the higher fraction of the population with some immunity to COVID-19.

As a nation, we’re in the situation depicted below.  The blue line is the first year of the pandemic, the red line is the second year.  Where it stops, that’s where we are right now.

I’m thrilled to see those low numbers on the William and Mary campus.  But I think it’s way too soon to declare victory.

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.

 

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.

 

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.  

 

 

Source of counts:  William and Mary COVID-19 dashboard.

Today’s case counts from William and Mary show a steady but high rate of new cases reported on campus.  Today’s 42 new cases is not materially different from yesterday’s 40 new cases. Continue reading Post #1243: To test or not to test?

In my last post on this topic, I had a hard time making sense of the numbers regarding COVID-19 cases at William and Mary.  Now I know more, and I’m passing that along.

All Virginia colleges are having some problems with COVID-19 this semester.  But  William and Mary appeared to have a worse-than-average problem, relative to the size of the  on-campus population.  They seemed to have more cases than you would expect for the Virginia college-age population as a whole, and more than appeared in the handful of universities I used as a comparison group.

Skip the next section if you just want to get to the numbers.  But in fact, the graphic above tells the story.  That’s why W&M is counting so many positive cases, relative to the number of persons they have tested.

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Background:  Deja vu all over again.

To be clear, William and Mary has emphasized that (as of three days ago) “all of those cases are experiencing no or mild symptoms.”  W&M’s contact tracing indicates that “All cases … spread through unmasked social interactions – often off-campus.”  I take the last part of that to be a euphemism for parties.  And that ” … there is no indication of spread in a classroom.”  (Source:  William and Mary messages to students.)

By my recollection, this is virtually identical to the situation last semester.  Parties were the problem.  (In particular, St. Patrick’s Day parties).  Classrooms were a non-issue.  And, unstated but probable, there is some amount of secondary spread by unmasked close contacts.  We know that COVID-19 spreads to a modest degree within households with an infected person (so-called “secondary attack”), I am guessing that some modest portion of the spread is within dorm rooms and suites.  I have seen nothing that directly verifies that.  But, presumably, that’s where most of your unmasked on-campus social interaction takes place.

As near as I can tell, this is the typical pattern for most U.S. colleges and universities.  So there’s nothing new here, either compared to W&M’s recent past or to the cross-section of U.S. colleges.

Really, the only changes from last year are that almost everybody is vaccinated to some degree, and the Delta variant is significantly more infectious (transmissible) than the Alpha variant which became prevalent prior to last semester’s St. Patrick’s Day outbreak.

Near as I can tell, those two factors — vaccination versus greater infectiousness — roughly cancel out, in terms of impact on spread of disease.  Vaccines reduce it, the greater infectiousness of the Delta variant increases it, and just by chance, they have roughly equal effects at the vaccination rates seen in the general population.

Given that, and given the high incidence of COVID-19 in the community generally, it’s not surprising to see some spread of COVID-19 on the W&M campus.  It’s not even really a surprise to see an outbreak, that is, multiple related cases occurring at the same time.

For what it’s worth, based on the calculations I’ve presented in this blog from time to time, the high vaccination rate on the W&M campus, combined with masking in social situations, should have prevented this outbreak.  Even with the higher infectiousness of the Delta variant.  Even with the lower efficacy of vaccines against the Delta variant.  So, to me, at the end of the day, it’s the “unmasked” part of the “unmasked social interactions” that’s the root cause.  The 93% vaccination rate plus rigorous COVID-19 hygiene should have made the campus immune to outbreaks.  But without the additional exposure reduction from masks, the 93% vaccination rate alone is right on the edge of being adequate to suppress a Delta variant outbreak.   You can see the rough calculation in Post #1160.

This is why you no longer hear anybody talking about “herd immunity”  any more.  Practically speaking, it’s impossible to achieve herd immunity (in the sense of “we can all go back to normal now and quit using masks”) in the general population with the Delta variant, given the efficacy of current vaccines.  You’d have to vaccinate people at gunpoint to achieve the >91% vaccination rate required.  At best, we can hope to use vaccines to reduce the size, extent, morbidity, and mortality associated with outbreaks.  But we aren’t going to be able to vaccinate enough of the general population to prevent outbreaks, absent some permanent and enforced mask mandate on top of the vaccination.

As was true last year, W&M administration has tightened up the rules in an attempt to stop this latest outbreak.  Indoor dining has been suspended.  Mask mandates have been expanded to include outdoor situations where you can’t maintain social distance.  If I had to guess, I interpret that last one as an attempt to avoid large unmasked crowds at (e.g.) sporting events.  Nothing could possibly look worse on the news than a big outbreak in the student population superimposed on a stadium full of unmasked cheering students.

My only point is that, in terms of COVID-19 levels on campus, the main difference between this year and last year is that there’s so much COVID-19 currently circulating in the general population.  We’re starting off from a much higher base rate of infections that was the case last semester.  The red circles show school opening last year versus this year.

Otherwise, near as I can tell, Delta variant versus vaccination rate is more-or-less a case of offsetting effects.  Unmasked parties are the problem.  Classrooms aren’t.  Deja vu all over again.

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Explaining the numbers.

William and Mary is counting all positive cases regardless of the source of information that a person is COVID-19 positive.   The count of COVID-19 positives includes individuals identified by William and Mary testing, and individuals identified by any other testing, including all individuals who self-identify as COVID-19 positive.

The count of tests, however, is just the count of tests administered by William and Mary.  It doesn’t even include the count of persons identified as positives via other testing or self-identification. 

The short answer is that you can’t calculate anything like a test positivity rate from those numbers.  The numerator effectively includes everyone.  The denominator includes that small subset of students tested for having close contacts with a known COVID-19 case.  To take it to the level of absurdity, there’s nothing that prevents the count of positives from exceeding the number of persons tested.

Further, it’s hard to be sure that I can legitimately compare the W&M number to other colleges and universities.  I’d have to find out the details of what they are reporting.   If a college is doing “screening”-type testing, and only reporting positives found by that, it’s not clear the results of that would be comparable to the results from William and Mary’s current approach.

The current W&M approach — count all positives from any source, only test individuals with known exposure — should yield a per-capita rate of infections that’s modestly higher than that found in the community.  All other things equal.  In effect, this is testing-for-cause, plus attempts at contact tracing for 100% of known cases.  What we have in the community is testing for cause, plus contact tracing for maybe 50% of known cases (see Post #1197).  If the underlying rates of infection are identical, we’d expect a modestly higher rate of new cases to be discovered in the W&M population.

That said, newly discovered infections continue apace.  I interpret the table below as showing that they’re still identifying cases from the initial outbreak.  I specifically don’t interpret these three days’ of data as showing that the outbreak is getting worse.

In any case, here’s the last three days of data from the William and Mary COVID-19 dashboard.  The rate of new case discovery per 100,000 population is very high, compared to what’s going on in the community.  I think that’s expected at the positive tests come in from the start of an outbreak.  It’s not good, but we’ll need to give it a few days to see whether or not this will slow down to a more normal level.

For what it’s worth, we can the current rate of daily new cases to last semester’s St. Patrick’s Day outbreak.  The chart below is my from my final look at that outbreak.

 

As you can see, the increase in positive cases that William and Mary is seeing currently (call it 23 per day, for the past two days) is about what they saw during the heart of last spring’s St. Patrick’s Day outbreak (circled above).

The upshot is that the current outbreak is as bad as, but no worse than, last semester’s St. Patrick’s Day outbreak.  Deja vu all over again.

I’m writing this post to provide a little perspective on the COVID-19 situation at William and Mary.  Yesterday they updated their dashboard to reveal that there have been 115 known cases on campus.

To reiterate what the William and Mary administration said about that, almost all the cases are mild or asymptomatic breakthrough infections.  (That they are almost all breakthrough is unsurprising, given that 93 percent of students report that they have been vaccinated.)

My main takeaways are that:

• Many Virginia universities and colleges are having a problem with COVID-19 in the 2021 fall semester.
• The rate of new cases showing up in Virginia universities seems roughly similar to the Virginia 18-24 population as a whole.
• William and Mary appears to have a much-worse-than-average problem this semester, based on a comparison to four other Virginia universities and to the current rate among all Virginia residents age 18 to 24.

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How does William and Mary compare to other Virginia universities? 

In a situation like this, it’s sometimes helpful to look around at the rest of the state (as in Post #788, last year).  Below I’ve quickly tabulated the numbers for a handful of Virginia universities.

This is a rough cut, in that some of these combine students and faculty, and some of the enrollments my overstate the actual residential enrollment to which the testing applies.  There’s nothing systematic about which universities I chose.  They were just the first ones to come to mind in this context.

The other unknown is the effective start date of the school year.  The longer they’ve been back on campus, presumably the more time they’ve had to identify infected students.  Radford, for example, began classes on 8/23/2021.  U Va started on 8/24/2021.  W&M began classes on 8/19/2021. 9/1/2021.  (I looked at the wrong calendar).  So W&M has had fewer person-days on campus in which to find infected individuals (or to have cases develop).

That said, at first blush, none of the numbers for William and Mary look good.  Every Virginia university is having some sort of a problem, but ours looks somewhat worse than the comparison group. A combination of fewer tests and more cases particularly stands out.

For the high level of active cases, that must be due to the fact that these are almost all newly-reported tests.  Which is consistent with the late date for start-of-classes.  By definition, I think cases are considered active for 14 days following positive diagnosis, unless symptoms persist beyond that point.  In other words, if almost all of those tests took place less than 14 days ago, then by definition, almost all of the cases will be considered “active”.

Not shown — and to me, by far the oddest aspect of the W&M counts — is that W&M found more than 100 cases by testing fewer than 400 people. It’s on-order-of a one-third positivity rate (infections to persons tested).

I can’t quite grasp how they could have done that.  I surely hope that’s due to testing symptomatic persons only, then following up with contact tracing.  That “target rich” testing pool could plausibly yield such a high positivity rate.  To be crystal clear, it’s not even remotely plausible that the high positivity rate shown reflects a cross-section of the campus population.

In any case, the main takeaway is that everybody is having a problem with COVID-19 in the Fall 2010 semester.  (I was going to say more of a problem than last year, but Radford had a terrible time last year.  Now they have just about the best numbers on the table.)

The plain reading of the numbers makes it look like more of a problem at William and Mary than elsewhere.  But the oddity of the testing numbers (100 positives out of 400 persons) means that William and Mary’s testing has been driven by symptomatic cases (and possibly contact tracing).  But everybody tests symptomatic individuals, so that, by itself, would not explain the higher numbers at William and Mary compared to Virginia peers.

 

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What are the rates of new COVID-19 cases in the college-age population of Virginia?

Data source for this graph of new case counts:  Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 9/4/2021, from https://github.com/nytimes/covid-19-data.”  The NY Times U.S. tracking page may be found at https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html.

It’s no secret that the overall rate of new cases is higher now than it was last fall. Above, you see the rate of new cases per 100,000 population per day for Virginia, in the first year of the pandemic and the second year of the pandemic.

It’s tough to compare the COVID-19 rates on these campuses to the COVID-19 infection rate in the community.  The problem is that we’re seeing cumulatives of all cases over some period of time, for the college data.  For the community, we’re seeing daily cases.

In short, I have to guess the number of days of exposure that have occurred so far, at these college campuses.  For example, I’d have to use a longer period to make the comparison to the colleges with early start dates, and a shorter period for comparison to colleges with more recent start dates.  Based on class start date for William and Mary (and arrival on campus prior to start of classes), I’m just going to use nice, round three and two week periods.  So for this next bit, I’m combining Census data showing 802,000 Virginia residents age 18-24, and Virginia Department of Health counts of new COVID-19 cases for that 18-24 population for the past three weeks, and then for the past two weeks.

And, for the past three weeks, for the Virginia age 18-24 population:

• 0.8% were diagnosed with COVID-19.
• 0.01% were hospitalized for COVID-19.
• 0.001% died from COVID-19.

For the past two weeks, for the Virginia age 18-24 population:

• 0.6% were diagnosed with COVID-19.
• 0.007% were hospitalized for COVID-19.
• 0.0006% died from COVID-19.

You have to be careful when comparing this to the college numbers because testing regimens may differ.  I would guess that asymptomatic cases are rarely diagnosed in the community.  They would only be found via contact tracing.  Colleges and universities, by contrast, may have a more systematic testing program in place, and so find a larger portion of cases.

That said, the all-Virginia estimate for this young-adult population is close to what we’re seeing in the schools above.  In some sense, that’s reassuring.  It’s not as if going off to college hugely increased risk, relative to staying home.

But William and Mary’s numbers again stand out as higher than expected.  Given the late start date, the William and Mary 1.7% number should be compared to the 0.6% observed in the college-age Virginia population over the past two weeks.

Honestly, I’m still puzzling over the fact that about a third of the students tested at William and Mary were positive.  And that the number of students that tested positive — so far — is running at a rate that’s about three times the community rate.  I’m wondering if they’re getting some false positives, as occurred during one episode last year.

But in another sense, it’s not a huge surprise that the average Virginia university has numbers close to the Virginia average for college-age persons.  To a large degree, we have to be looking at literally the same people.  Virginia colleges have about 500,000 enrolled, excluding one university claiming large virtual enrollment, versus 800,000 in the 18-24 age group.