What Northam’s “Key Measures” Do and Don’t Tell Him

Source: Virginia Department of Health COVID-19 dashboard

by James A. Bacon

Later today Governor Ralph Northam will issue his mask-wearing mandate for Virginians. I’ll reserve comment about the details of the plan for when I see them. In the meantime, it is worth considering what data he might draw upon to justify his measures.

The Virginia Department of Health COVID-19 dashboard highlights several “key measures.” One, seen above, tracks the total number of COVID-19 cases. This particular graph strongly suggests that the COVID-19 epidemic is spreading as rapidly as it ever was — indeed it has ticked back up in recent days.

Reinforcing this impression, today’s VDH dashboard reports a record increase of new confirmed COVID-19 cases — 1,615. Data compiled over the weekend is subject to jinky behavior due to reporting delays, but that number follows 1,483 cases the day before. So, if the Governor wants to make the case that the coronavirus is still spreading, there is data to support him. The Washington Post, which can scarcely keep its pro-shutdown sentiments out of its news articles, picked up on the latter number in its news headline this morning — and we all know that Northam (or his people) pay close attention to the WaPo’s coverage.


What the Post neglected to report (I won’t speculate upon the reason) is that Virginia is finally experiencing its long-promised surge in testing. The VDH website reports more than 36,000 tests over the past three days, compared to 20,000 over the previous three-day period and 22,000 the three days before that.

All other things being equal, more tests = more confirmed cases. It is difficult to know if the increased number of confirmed cases should be attributed to actual spread of the disease or the increased frequency of testing subject to VDH protocols and priorities.

That’s why the VDH key measures also includes a graph showing the percentage of tests that are positive. The idea is that if the percentage of positive tests is declining, the virus may be retreating.

Source: Virginia Department of Health COVID-19 dashboard

But there are problems with this graph, too. To some degree, it compares apples to oranges. In the early days of the epidemic, tests were scarce, and hospitals and public health authorities reserved tests to confirm what, based on symptoms and severity, seemed to be the most likely and most acute cases. Some days the percentage of positive tests exceeded 30%, and the seven-day moving average, as shown above, exceeded 25%. As testing became more available, especially by private labs, the tests came to reflect the prevalence of the disease in the broader population where, not surprisingly, the incidence was lower than in hospital sick wards.

A different measure, not subject to such testing biases, suggests that the spread is receding markedly. When people get extremely sick, they check into the hospital. VDH data captures the full universe of COVID-19 patients admitted to the hospital, not a small and potentially biased sample. The trend of hospitalizations is clearly down.


While the epidemic may be losing momentum, the COVID-19 virus is still out there. And it is still spreading in the community. Although deaths have been concentrated in nursing homes — almost three out of five statewide — the cases have been broadly diffused overall. Outbreaks of 10 or more cases in a single setting account for only 18% of all confirmed cases.

Clearly, some caution is still called for. I, for one, eagerly await the Governor’s announcement.

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5 responses to “What Northam’s “Key Measures” Do and Don’t Tell Him”

  1. Steve Haner Avatar
    Steve Haner

    We ain’t getting beyond Phase 1 next week…..

  2. LarrytheG Avatar

    I think it’s pretty easy to get tangled up in the data and graphs. Not saying it should not be generated – but the quality of the data and layman versus professional interpretation of it is an issue.

    The professionals know more about the nature of the data and it’s peices and parts relative importance whereas lay people don’t usually and just use their own non-direct-academic perspective to decide.

    But that’s also where the culture divides incubates… because whatever Northam does or not – he WILL BE ATTACKED as not justified and the attackers will dredge up the data… as this has been – ongoing… since the pandemic began…

    So..we’re just setting the stage here… odds are… no matter what Northam does – the hammer comes down… it’s just where to aim it that will be decided when he lays out his plan…

    been there, done that, over and over and over and over……..blah

  3. TooManyTaxes Avatar

    Jeff McKay spoke to the annual meeting of the McLean Citizens Association via Zoom on May 21. One of his main points was the absolute necessity to get to Phase 2 as soon as it can be done safely. He and, presumably, his colleagues are well aware that the economy needs to be opened up very soon.

    Larry, to the extent Northam is being attacked by his enemies, he’s also being praised by his supporters, including the MSM. The truth is probably some place in the middle. That’s one of the big problems with both the Media and the widening divide in the United States. There’s no recognition of bias on all sides. Read former CBS News President Van Gordon Sauter’s Sunday Op-Ed in the WSJ.

  4. LarrytheG Avatar

    Well TMT, actually he’s NOT being “praised” that I can see….

    but the real point here is how to get to phase 2 as you said.

    And it ought to be with testing, contact tracing, and other measures like masks when social distancing is not adequate.

    common sense measures… and where are the opponents?

    they’re basically saying “open up now and get that good ole herd immunity”.

    they do not support testing nor contact tracing nor masks..so what exactly do they support? How can we find middle ground?

  5. A good way to begin to improve confidence and trust in VDH could start with keeping reports up to date.

    What happened to the 510 chicken plant cases in Accomack that had to be added manually? Accomack is only up 110 since May 15 when the 510 was announced. “Some” cases were from out of state VDH said.

    5/18 Wavy.com: “On Friday, VDH said “about 85″ of the 510 cases were included for Accomack & Northampton’s data. Few have been added since. VDH says labs used were not connected to VDH’s system/cases have to be added manually.”

    No footnote on the chicken workers’ positive cases.
    The footnote that VDH had not entered all faxed negative reports from new labs is gone. Do we have any assurance they have now been entered?
    Or did they notice we were watching and delete the note so when they add do 200-300 or more chicken plant cases (and who knows how many others) more than two weeks later they can say it’s a resurgence?

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