Author: P Hasselbacher

Reopening Kentucky’s Economy in the Current Covid-19 Epidemic.

How will we know if we are still ahead?

It had to start sometime, but pressure from partisan and a variety of other assemblies have surely advanced the nation-wide schedule for lifting restrictions of non-medicinal management of the Covid-19 epidemic. It is happening in Kentucky too. While there are state differences in degree, the number of new cases identified continues to increase overall. We are “bending the curve.” Because availability of viral testing continues to be limited, as more testing done more cases will be found. How best should we monitor our populations to detect, localize, and quantitate any significant second peak in the curve of disease incidence? I cannot say that I know!

Kentucky has been fortunate to have acted early and aggressively to deal with our rising number of cases. Despite relative success compared to other states, the number of known cases in Kentucky is rising and will continue to do so while our still-modest ability to test for the virus increases. A 7-Day rolling average of daily new cases remains high. Timely identification of new cases will be essential to deal with the brushfire outbreaks that are certain to occur in the months ahead– whatever we do. Depending on the day of the week, the number of tests done, and reporting from new hot-spots, the number of new cases per day varies widely, making predictions uncertain..

Continue reading “Reopening Kentucky’s Economy in the Current Covid-19 Epidemic.”

It Cannot Yet Be Said That We Have Reached Plateau In Kentucky’s Covid-19 Epidemic.

[See addendum at end for an update.]

It has been 46 days since the first case of Covid-19 infection was reported in Kentucky and 36 days since the first death– not as long as it seems for those of us riding out the storm at home or still on the job.! Nonetheless, we are hearing increasingly broad demands to walk away from the non-medical public health approaches we are using to mitigate the impact of this highly infectious agent. However, given the very limited availability of viral testing, of what is at best a decrease in the exponential growth rate of new cases, and continuing sporadic jumps in the number of new deaths daily; it is not at all clear that we have broken the back of Kentucky’s part of this pandemic. It does appear that our personal and other community sacrifices have awarded us success compared to other states! We have avoided a disabling flood of very sick Covid-19 patients on the capacity of our hospitals– one of our most important goals. However, in my opinion and as based on the raw numbers available to me, we do not have the evidence in-hand to declare that we have reached the plateau needed to justify anything more than thoughtful planning for progressive gradual stand-downs. The lack of a fully functioning viral testing and reporting system has not reached anyone’s minimal expectations. We are flying blind. Governor Beshear’s reports over the weekend through Tuesday evening show continuing substantial volatility in the counts.

Continue reading “It Cannot Yet Be Said That We Have Reached Plateau In Kentucky’s Covid-19 Epidemic.”

New Cases and Deaths in Kentucky Declining but Availability of Testing is an Issue.

The number of new cases of corona virus announced by the Governor last evening was not as high as was feared. There was concern that changes in data collection techniques would cause an artifactual “catch-up” spike. The aggregate numbers of both cases and deaths is still rising but not as strongly exponential as before.  The daily count of new cases may be leveling off, but the number of viral tests performed daily is also declining.  Current case mortality is hovering at 5% of identified cases. The percent of viral tests that are positive has been slowly rising– currently 8.2%. Both of these latter two statistics reflect the fact that sicker and high-risk individuals are still being preferentially tested.  As long as we are hamstrung by lack of testing capacity and timely reporting, Kentucky is in no position to open up its economy by relaxing the fundamental epidemiological principles necessary to control this extraordinarily infectious agent.

This morning I simplified and updated the data visualizations currently on the Tableau Public pages of KHPI.  I include some of the semi-log plots that I discussed yesterday, but as it happens, the aggregate numbers of cases and deaths are falling off even this trend line.  Visual inspection confirms that the plots are rising less steeply especially for the number of aggregate cases. (Aggregate deaths might be expected to lag new case discovery.)  Muddying the water however, is the fact that rather than increasing, the number of tests performed (and reported publicly) is actually declining!  What is not looked for is rarely found.  We are still largely flying in twilight– if not the dark.

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Tracking Kentucky’s Covid-19 Epidemic

How will we know when we have won?

[Addendum: I have updated the Tableau Pubic presentation with data from Friday April 17. The increase in cases and deaths was not as great as the Governor feared. It looks to me like the rate of increase in both cases and deaths no longer fits an exponential trend curve. Things look like they are slowing down! Overall however, both measures continue to increase. I will address this new data later.]

I have been tracking and commenting on the number of cases and deaths from Kentucky’s coronavirus epidemic. Despite my best effort’s and some requests, the only data I have from Kentucky proper is what has been announced from the governors office during his evening greetings. Given our national slow start in timely testing for the virus, we must assume that the numbers as presented are incomplete– indeed only the tip of the iceberg. We have been warned over the past two evenings, that as data collection is now more systematized, that tonight we should expect a large number of “catch up” cases. For that reason I have not yet updated the numbers in my earlier articles or on my Tableau Public website. 

In the meantime, I have been evaluating further the approaches I have been using to visualize the numbers released. Because we are still in the exponential expansion phase of this epidemic and because of some unavoidable scatter in the data, it is very difficult to determine if we are bending our new-case curve, let alone flattening it. It is certain that we have not yet reached the peak incidence of this epidemic.

Are we bending our curve yet?
When a curve on a simple graph plot is going straight up, it is difficult to know when it will stop. For this reason, I have begun using what is called a semi-log plot that allows simultaneous visualization both high and low numbers, and transforms an exponential curve into a straight line. This is a technique used by experienced epidemiologists (of which I am admittedly not one).  In doing so, I wanted to feel more confident with the significance of the observation that the data-points of both new cases and deaths from earlier this this week appeared to be falling below the predicted trend-line. That would be nice!  There are lots of understandable reasons why that may not be happening including more testing, clusters of deaths in long-term care facilities, more impatient violations of large group gatherings, and the like.

My goal here.
While I am waiting for tonight’s updated numbers, I wanted to try some alternate methods of visualizing the data and get a feel for how reliable they might be in identifying and impact of what we are all trying to do together. I am feeling more confident that using semi-logarithmic plots and applying exponential regression analysis can be useful in identifying trends.  Because I find that experts commonly, if not by standard, exclude cases before the 100th when attempting to predict the future.  (Early data may be collected in a less formal manner and the randomness inherent in low numbers may offer less predictive value.)  I placed a presentation on my Tableau Public website that steps through my thinking. This is what I expect to try in future articles.

Even with all the caveats.
Looking at the various plots and making assumptions about how infectious agent like Covid-19 might be, I was stunned (but should not have been) at the power of exponential (compound) growth.  I start from a single case from a hypothetical virus and uses purely hypothetical data. Even if a single infected person passes the disease to only one out of a thousand other people, the number of new cases in Kentucky would be in the tens or hundreds of thousands within 40 days.   In addition, I am impressed at how fast things can sneak up on you!

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