Post #712: Key graphs updated to 6/11/2020.

Posted on June 11, 2020

This post updates some key graphs to 6/11/2020.  At the last update (6/6/2020), it looked like we were finally seeing a slowdown in new case growth in Fairfax and in Virginia (Post #704).  That has panned out.  For Fairfax County, the seven-day moving average of daily new cases is down to about 150 new cases per day.  For Virginia, it’s down to 750 new cases per day.  For Vienna (ZIP 22180), it’s down to maybe one new case per day.

Whatever we’re doing under Phase I of re-opening, it’s not creating a spike in new cases.  If there are new cases attributable to this modest relaxation of restrictions, they are being swamped by ongoing trends that have nothing to do with re-opening.  Near as I can tell, the trends in case counts have nothing to do with re-opening or not, in Virginia.

This matches my earlier analysis of US national data, and appears to match the European re-opening experience, as reported here.  I need to revisit the national data in light of recent events (e.g., in Arizona).

Impact of re-opening, Phase I, in Virginia, update to 6/11/2020.  The only discernible impact of Virginia’s re-opening plan is that growth in new cases in the “late” re-opening areas (NoVA, Richmond City, Accomack County) slowed to match case growth in the rest of the state.

Here’s the graph of total cases.  You can see that the blue line (“late” areas) curves slightly, so that the slope now matches that of the red line (“early” areas).

Source:  Analysis of county-level data as reported by the Virginia Department of Health.  NoVA plus is Northern Virginia, Richmond City, and Accomack County.  The latter is in the late-reopening group because because they had 500+ cases of COVID-19 in two poultry processing plants.

The story is a lot easier to see if I plot daily new cases, instead of cumulative cases.  That’s below, for the past 28 days.  Over the past month, case growth in the late-reopening areas has slowed down to match that in the rest of the state.

Read into those whatever you want to.  For myself, I find it hard to attribute anything on these graphs to the act of re-opening.  To me, having looked at health care data for much of my career, I’d say that whatever’s creating these new cases has more-or-less nothing to do with Phase I re-opening.

It’s too soon to tell whether Phase II of re-opening has any impact.  That only started on 6/5/2020 in the early-re-opening areas.  Under Phase II, e.g., restaurants and gyms are open for limited indoor service, and the (legally allowed) size of indoor gatherings increases to 50.

Source:  As above

A final note is that the late-opening areas still have more new cases per capita than the rest of the state.  So while the raw count of  new cases is about the same, the new cases per resident is still substantially higher in the late-opening areas.  As shown below.

Source:  As above, population counts are 2019 Census projections.


Total cases, Vienna ZIP codes, counts for 22180 shown, update to 6/11/2020.  There have been no net* new cases in Vienna (22180) for the past four days.  That strikes me as being significantly different from the roughly 5 per day occurring two weeks ago, then then three per day occurring last week.

* If you look closely, you can see that the 22180 case count actually fell a bit over the past two days.  That’s presumably due to cases that were classified as probably COVID-19 (based on symptoms and/or proximity to a known case) that turned out not to be COVID-19, after DNA (PCR) testing.  Those small corrections occur all the time, but aren’t normally visible against a background of rising case counts.  In total, such “probable” cases only amount to about 5% of all cases counted as COVID-19.

Daily new cases, Virginia and Fairfax County, last 28 days, update to 6/11/2020.  The dropoff in new cases that started last week continued into this week.  The seven-day moving average is now down to 750 cases per day in Virginia, and 150 cases per day in Fairfax County.  As you can see from the graphs, that’s down from well over 1000 and about 300 per day, just two weeks ago.

For me, it’s easier to grasp this when I look at the numbers, tabulated.  Two weeks ago, Virginia saw more 7000 new cases.  Now, it’s below 5000 per week (yellow).  Fairfax saw almost 2000 two weeks back, and this past week, it was down below 1000 (orange).