Bacon's Rebellion

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Tracking COVID-19 Cases in Virginia

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by

James A. Bacon
in

Coronavirus cases reported by the Virginia Department of Health have continued to increase in recent days, but they do not appear to be increasing at an accelerating rate. Whether these numbers accurately reflect reality or just the paucity of testing kits remains to be seen. If the impression is accurate, it is heartening indeed: The social distancing measures adopted voluntarily and imposed by public health authorities seem to be working. But the shape of the curve may change dramatically when more kits become available in the next few days and authorities begin taking more tests.

The VDH website displays the cumulative number of reported coronavirus cases on any given day, but it does not show the slope of the curve, so it is impossible to gauge whether the progression of the epidemic in Virginia is accelerating or decelerating. I will endeavor, as time allows, to keep the numbers updated.

— JAB

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17 responses to “Tracking COVID-19 Cases in Virginia”

  1. LarrytheG Avatar
    LarrytheG

    and this:

    Virus fears fuel spike in sales of guns and ammunition
    Just as grocery stores have been stripped bare by Americans panicked by coronavirus, guns and ammo have been flying off the shelves too.

    The world’s largest gun store, in metro Atlanta, has had lines that are six and eight people deep. A gun store in Los Angeles had lines that stretched down the block. And at least one store in Idaho put limits on sales after its shelves were nearly cleared out.

    Just as grocery stores have been stripped bare by Americans panicked by coronavirus, guns and ammunition have started flying off the shelves. Retailers say the buying frenzy is being fueled by consumers who are worried that people are becoming so desperate and unpredictable, they need to ensure they can protect themselves.

    “It’s been insane,” said Jay Wallace, who owns Adventure Outdoors in Smyrna, Georgia, adding that his ammunition sales are up more than five times the usual numbers. “This is like a Rod Serling ‘Twilight Zone’ episode.”

    It will be interesting to see if things like crime, robberies, and murder go up or down in the coming weeks and months.

    Restaurant workers? I wonder how many are going to convert to DoorDash or GrubHub workers?

    Grocery pickup and deliveries right now are overwhelmed… local stores are saying “no availability”. Perhaps this eases up as the public calms down and has less panic?

    How about transit – will METRO shut down?

    How about Uber?

    How about Doctor’s offices?

    etc, etc..

    It seems that the more we get recommendations – the more questions pop up and judging from the gun sales – there’s a certain amount of fear and lack of confidence in law enforcement being able to function effectively.

    We’re going to be doing things we never expected to do and though we may not recognize it yet – this will produce insights that we would not have without this change. And after this, minds might change about a lot of things.

  2. TooManyTaxes Avatar
    TooManyTaxes

    WMATA has put both its rail and bus services on a limited schedule (12 minutes between trains and a somewhat bolstered Saturday schedule for buses). My dentist is closing for two weeks absent an emergency. My wife saw more stocked shelves in Safeway yesterday (don’t know about Giant or other chains). Our law office is working from home absent a need to go to the office with one support person coming in to see whether we have any mail. Just a snapshot from McLean.

  3. djrippert Avatar
    djrippert

    All kinds of fresh chicken, ground beef and toilet paper gone from my local Safeway. Most people seem to be working from home. Local BBQ restaurant (Mookie’s) has voluntarily closed in-restaurant service and has initiated its first ever delivery service (curbside and to your home).

    Given the odd choices at the grocery store and what’s in our pantry I feel like a contestant on Chopped every time I make a meal.

    DC looking like a developing hotspot with 23 cases.

  4. LarrytheG Avatar
    LarrytheG

    The toilet paper is the most odd thing.

    The experts have been saying over and over that this is NOT “that” kind of flu but apparently to no avail.

    and as far as “social distancing” is concerned – look at this:

    https://i.cbc.ca/1.5498630.1584303334!/fileImage/httpImage/image.jpg_gen/derivatives/16x9_780/shoppers-stock-up-after-prime-minister-announces-financial-stimulus-package-and-no-non-essential-travel.jpg

    We’re going to lose some of us, maybe a lot, but the economic damage is going to be catastrophic… and may well take months or years to recover and some businesses may just disappear altogether. Others actually may thrive – deliveries and online!

    People that are retired and getting monthly pension checks are have a totally different perspective than those who have jobs in the private sector and carnage is ongoing.

    Those who live in rural or even suburban areas are going to have a different perspective than those that live in cities and dense urban areas especially those with pets.

    Sanitation – and the people that do that work – must continue and that means they’re going to be at risk just like medical care people are.

    And Gawd Forbid – all that TP makes it’s way to the wastewater treatment plants………

    and for us, it did not take long, the Fridge is out from it’s cubby hole and we’re cleaning out 10 years of dust balls and other assorted ick… but the good news, no mice droppings!

    and finally, I’ve heard not one person say “get the govt out of this!” !!

  5. T. Boyd Avatar
    T. Boyd

    Thanks for this analysis. I have been trying to fit an exponential curve to the data, but I agree – the slowing down of the acceleration of last week’s new confirmed cases in Virginia may indicate a slowing of the spread, or it may be because of the limited testing going on. My model, which I correct daily can be seen in a public google drive spread sheet at: https://docs.google.com/spreadsheets/d/1ZbE50UE2e5B74gbbjSQ_GiB2kSxRtQwNJHzl_pX1Mj4/edit?usp=sharing . In the top left hand corner you can see the number of days chosen as the doubling rate – as of yesterday, I set it at 1.5 days. The published “doubling rate” – I have heard 3 days and 6 days – either one of those really predict a very dire future, but starting with March 9 when we had 3 confirmed cases, both of those rates gave much lower number of cases for the end of the week.

    1. djrippert Avatar
      djrippert

      Great spreadsheet and graph. Thanks for sharing. I’ve read so much about this over the past few days I can’t remember where I read that the doubling factor was assumed to be every 5 days. Also, Governor Northam held a press conference where 15 new cases were announced in Virginia so I guess we’re at 67. Obviously, today is not over. Looking at your graph … another 15+ today looks like the curve is bending toward a more exponential curve.

  6. James A. Bacon Avatar
    James A. Bacon

    Here’s what T. Boyd’s graph looks like:

    https://www.baconsrebellion.com/app/uploads/2020/03/predicted_versus_reported.jpg

    The key assumption here is the modeled rate of spread. Perhaps that can be adjusted as we get more data.

    1. djrippert Avatar
      djrippert

      The rate of spread is an input but T Boyd (wisely) has set his graph for read only. I believe the graph you published is a 1.5 day doubling.

  7. T. Boyd Avatar
    T. Boyd

    I just changed the rate of increase to 1.6 days instead of 1.5, and brought today’s prediction in line with the actual value. It predicts 96 by tomorrow

  8. LarrytheG Avatar
    LarrytheG

    My ignorance but do all of these things double at one rate or is the rate of doubling specific to a given unique virus?

  9. T. Boyd Avatar
    T. Boyd

    LarrytheG: The model I set up was just based on confirmed cases which may or may not track as the number of real cases that are happening. I think this rate depends not just on how volatile the virus is itself, but on the characteristics of the people themselves. If the precautions that the health experts were to be ignored, the doubling rate might stay at the worst predicted or measured rate; but if the precautions are being observed by everyone, then it should slow way down. That is my opinion which is not at all in the expert realm. 🙂

  10. LarrytheG Avatar
    LarrytheG

    Thanks. and the predicted rate based on…??? Is there some standard for “predicted” when it comes to this kind of thing?’

    maybe based on past contagions?

    again.. ignorance…

    1. T. Boyd Avatar
      T. Boyd

      When I heard a pandemic can grow exponentially, and then I saw Virginia’s reported cases went from 3 on last Monday, to 9 on Wednesday, and 30 on Friday, I wondered what math formula would fit that data? So I took the simplest example I knew and tried it out in the spread sheet. I adjusted the doubling rate to fit the reports, and I have daily readjusted that rate in my math formula to fit the data. Today’s doubling rate is 1.5 days, meaning that the number today will double in 1.5 days. I ignored other reported rates and only worked on our own state. And again: this only predicts the reported cases, not the actual cases, which population might very much differently. I hope that helps. A Wikipedia page on it is at https://en.wikipedia.org/wiki/Exponential_growth
      Boyd

      1. LarrytheG Avatar
        LarrytheG

        Good, and thanks much!

  11. T. Boyd Avatar
    T. Boyd

    I have added another chart based on a power series fit which does better than the exponential fit. When you look at the spread sheet the tabs at the bottom show the two different fits. The new fit predicts that in 2-3 days the increase is much more moderate. https://docs.google.com/spreadsheets/d/1ZbE50UE2e5B74gbbjSQ_GiB2kSxRtQwNJHzl_pX1Mj4/edit?usp=sharing

  12. LarrytheG Avatar
    LarrytheG

    I’m quite envious of your abilities with spreadsheet, graphs AND curve-fitting!

    thank you!

  13. T. Boyd Avatar
    T. Boyd

    It is fun. I wish I could remember more about how I used to do it back in the 1970’s. But thanks for the kudos.

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