Kentucky and many other states are backing away from public health measures of varying strictness that were adopted in March or April during the exponential expansion phase of the Covid-19 pandemic in the United States. It is appropriate and even necessary to begin this process, but it needs to be done with an acceptable degree of safety. There is no doubt that measures taken so far have at least “bent” the curve, slowing down if not ultimately decreasing the mortality and morbidity of this overtly infectious disease. I believe Kentucky has benefited greatly from our collective efforts despite opposition on several fronts including armed protest. The expectation and promise is that we and the nation will be able to detect “surges” of the epidemic in a timely way and to be able to reinstate restrictions on public interactions that have proven effective. I wish I could be more confident that we can be successful in either instance.
It‘s not over yet.
In the nation as a whole, albeit to a lesser degree in Kentucky, both the number of aggregate cases and deaths continue to increase. Our ability both as a nation and Commonwealth to test for, identify, and report the presence of Covid-19 in the community and to trace exposed persons is still far behind what is needed to detect and respond to localized outbreaks before they show up two or three weeks later as increases in hospitalizations and deaths. It is from such localized hotspots that epidemic expansion can be continuously fueled. More troublesome is a background of resistance from individuals and groups which, for a variety of ideological, religious, political, or business reasons, hold the nation hostage by refusing to follow evidence-based public health initiatives that are effective only when done collectively. Unfortunately, we face these problems with a weakened and fragmented public health system and an inequitably distributed healthcare system overall.
How will we see a “surge” coming?
As the world tiptoes its way through its “reopening'” in the middle of an active pandemic that has no demonstrably effective specific treatment or vaccine yet, how can we feel comfortable that things are not getting unacceptably worse? I do not believe this is a straightforward undertaking. As testing and reporting increase, it is inevitable that new cases will continue to be discovered in new places here and around the world. The most objective indicators of epidemic expansion commonly reported are the number of deaths or hospitalizations attributed to Covid-19. However, either of these, even if consistently reported, are late markers of community epidemic status. The virus has first to find a human host, to incubate asymptomatically, to be recognized in the healthcare system as a clinical infection, to be reported to some public health entity, to be evaluated in the context of current community experience, to be recognized as a diversion from the status quo, and only then to pass some threshold to take effective public health action. Seems to me that by this time, the virus is already out of the barn, racing down the track, and harder to stop.
Who is keeping track?
Compounding the difficulty is that there appears to be no national standard for how to define the items to be reported or even to report them at all. For example, not all states have been reporting hospital or ICU admissions. I can find no federal database at the Center for Communicable Diseases that local communities of public health researchers can draw on. The challenge of aggregating a national experience has been assumed by institutions such as Johns’ Hopkins University, or the New York Times, or The Atlantic magazine that are collecting relevant data directly from individual state and international public health sources. Reporting on weekends is not common nationally and has led to large swings in daily new cases or deaths making timely detection of deviations from the expected much more difficult. Even if a single state, county, or community is doing everything right, it is at the mercy of its neighbors. What happens in Indiana, Ohio, Illinois, Missouri, Tennessee, Virginia, or West Virginia– indeed anywhere in the world– does not stay in those places. At least one of our neighboring states appears still to be in a state of active exponential growth even before “opening up.” How then can we compare our experience with that of other countries, states, or communities?
Below is a plot of aggregate cases of Covid-19 in neighboring states. I use data from the Covid-19 Tracking Project as of May 5th. I plan to work with this or similar data further in the days ahead to compare what unfolds. View the interactive series of data visualizations here.
How about Kentucky now?
Readers of these pages will have watched me try to interpret Kentucky’s own data collected from Governor Andy Beshear’s evening reports. [There is no consolidated Covid-19 database of Kentucky’s epidemic experience available to me. Is it available to anyone?] I conclude that we have markedly slowed down the rate of expansion of the epidemic in our state, but have not yet entirely stopped its ongoing growth. As testing is now rapidly improving, we should expect to see more new cases emerge, especially in places where two or three are now gathering together. More troubling is a recent rise in deaths and continuing new ICU admissions. Take a look at what I have published and tell me what you would follow or substitute.
Basic Reproductive Number.
As I wait to be better informed, I use this opportunity to suggest an additional marker of epidemic status that is being used worldwide to monitor the opening-up of communities around the world. I suggest an estimate of the current Basic Reproductive Number of the virus, or “R.” A reproductive number represents the average number of people that a single infected person can infect. If R is greater than one, an epidemic is still expanding exponentially. (Think compound interest!) If R is less than one, the epidemic may be on a course to burn itself out. An R of zero indicates that there are no more new cases.
The most accurate estimation of R (R0 or R-naught) requires higher math and a fuller knowledge of epidemic parameters that is only available in retrospect. The version of basic R that I have incorporated into KHPI’s data visualizations of Kentucky’s experience is that recommended by Germany’s Robert Koch Institute– that country’s version of our CDC. [Robert Koch was the 1905 Nobel Prize winner in Medicine and is considered to be a founding father of the sciences of bacteriology and infectious disease.] This version of R depends only on the number of new cases detected daily. It compares the 4-day rolling average value of new cases on one day with the corresponding average value four days before. Brought down from an initial high of 3.5 in March, Kentucky’s “R” is currently hovering on both sides of 1 trying to decide where it wants to go. I would not venture to say at this time. View an interactive version of the figures below here.
Here is how Kentucky’s “R” compares to a 7-Day rolling average of new cases.
We are by definition all in this together and will get through it together– one way or the other. We owe it to each other to do it respectful of each other’s needs and safety.
Peter Hasselbacher, MD
Emeritus Professor of Medicine, UofL
20 May 2020
[Addendum May 21, 2020: During last evening’s Governor’s report, the number of patients in ICUs reported fell from 269 to 98 in a single day. They did not go home overnight! It was revealed that the hospital reporting process was broken somewhere along the line. Since availability of hospital beds is one of the more important planning priorities and should be a marker to detect new outbreaks, this is not a minor matter. All hospitals use or should be using electronic medical records. My practicing physician friends often complain that these record systems seem designed primarily to capture billing and payer accountability matters, often getting in the way of direct patient care. If the different brands of hospital electronic record systems are not able to support universal public heath needs, I think we need different systems, perhaps even a single one! It is one thing for one brand of EMR not to be able to talk to other proprietary ones. It is another if they are impediments to public health data needs.]