Post #775: Modest decline in new coronavirus cases in Virginia

My three standard graphs, updated to today (8/15/2020), are given at the end of this post.  They don’t look materially different from (say) two weeks ago.  Virginia is getting about 1000 new cases per day, Fairfax is getting maybe 60, Vienna (22180) is getting about one new case per day.

But beneath that state-wide stability there are some interesting trends.  In particular, I wanted to step back and look at the Hampton Roads area.

Here’s the story for now.

If you go back to July 1, Virginia had under 600 new COVID-19 cases per day, and that seemed fairly stable (Post #738).  But it wasn’t.  By July 20th, that had risen to about 1000 new cases per day (Post #762).  That increase was attributed largely to the Hampton Roads area.  In particular, to an uptick in cases among young adults (age 21 to 30) in that area (Post #758).

On July 28, the Governor “rolled back” some aspects of reopening in the Hampton Roads area.   This placed additional restrictions on restaurants, alcohol service, and large gatherings.  This was more-or-less based on the assumption that the disease was being spread by young adults socializing in densely packed crowds, such you might find in a bar.

I had some vague notion that maybe the recent dip in cases was the result of that.  But when I looked at the data for the past month, all I got was confused.  I had to take a longer perspective to see that the Governor’s action appears to be a case of shutting the barn door after the horse had gone.

Here’s a three-month perspective on daily new cases in the Hampton Roads area, versus the rest of the state.  Below, the yellow line is the Hampton Roads area, and the blue line is the rest of the state.

Defined as the area where additional restrictions were imposed:   the cities of Virginia Beach, Norfolk, Chesapeake, Portsmouth, Suffolk, Hampton, Newport News, Poquoson and Williamsburg, as well as York and James City counties. 

 

The first part of the story above appears correct.  As you can see, in the first two weeks of July, the Hampton Roads area (yellow) saw a large increase in daily new cases.

What’s interesting, through, is that the increase had leveled out well before the Governor issued his most recent order (July 28).  In fact, daily new cases in the Hampton Roads area had begun to decline well before the impact of the Governor’s orders could have plausibly been seen in the data.  (By my estimate, about 12 days later, or August 9).

And so, while the Governor’s additional restrictions on Hampton Roads may have been a reasonable precaution, a) I don’t think we can credit the those restrictions with the decline and yet b) Hampton Roads is no longer the main driver of daily new cases.  I would expect the Governor to remove those additional restrictions soon, given how this is playing out.

At this point (see below), Northern Virginia/Richmond and Hampton Roads areas both seem to be under control.  That’s pretty much the entire densely urbanized portion of the state.  If there are trouble spots in Virginia, they’ll be outside of those areas.

At this point, I have to wonder what fraction of the daily new cases are arising from outbreaks.  Both the type that Virginia tracked all along (prisons, health care facilities, schools), and new ones that it only recently began tracking (meat packing plants).  And maybe others.

My three routine charts follow.


Trend in new cases, Virginia (blue) and Fairfax County (Orange).

Early-reopening areas (NoVA, Richmond, Accomack, blue) versus rest-of-state (orange)

Town of Vienna ZIP codes.