I began writing about COVID-19 out of frustration. In the early days of the coronavirus pandemic, the reporting often placed panic-inducing headlines on inaccurate or incomplete data analysis.
Sadly, history may be repeating itself. Over the past two weeks, the news media have been citing increasing positive test results as evidence that California has reopened too quickly and the coronavirus is now spreading at such an alarming rate that we are nearing a crisis.
Gov. Gavin Newsom may share these concerns — over the past 10 days, he has issued orders mandating masks in public and closing bars in certain counties.
As we adapt to living with the coronavirus, it is critical that we base our public health policies on accurate and complete data assessments.
If we were to do that today, we would see that our statewide COVID-19 numbers are growing, but remain quite manageable. We would also see that the next week would provide us with the data we need to more accurately assess the true trajectory of the virus, the impact of the mask order and the potential need for additional public health measures.
What numbers should we be using to monitor the trajectory of the coronavirus? As I have stated repeatedly, the optimal approach to measuring the trajectory of the virus would be random testing of a sufficient number of people from different geographic areas at regular intervals. But we do not do this type of testing for active infections or antibodies.
What number should we not rely on? Daily positive test results.
This number may not accurately reflect the spread of the coronavirus for many reasons, including the fact that the volume of tests performed changes every day, the criteria for testing eligibility change often, and the mix of people being tested (e.g., hospital patients, symptomatic individuals, contact-traced individuals, asymptomatic individuals) varies every day and can affect the positivity rate.
Indeed, depending on this mix, obtaining positive test results could be the functional equivalent of shooting fish in a barrel or trying to find a needle in a haystack. For these reasons, epidemiologists recommend tracking hospitalizations as the best measure of community spread, at least as an early warning mechanism. (Fatalities may also be a useful measure, but they can trail the date of infection by more than 30 days in some cases.)
Unfortunately, California does not report the most useful hospitalization metric: new daily admissions (although an incomplete record of this data is available through the state data portal). Instead, it reports a net hospitalization total each day, which is the result of new admissions minus daily discharges.
For this and other reasons, changes in daily hospitalization totals signal — but do not precisely mirror — the rate of community spread. Nonetheless, they are the best available measure of the trajectory of the COVID-19 virus (and it is possible to model the relationship between net hospitalizations and viral growth rates to improve precision).
So what do the hospitalization numbers tell us about our reopening? For California as a whole, they tell us to stay calm, recognize that the reopening went smoothly until June 6, and be patient for another week before deciding whether to recalibrate public health policies (although this ship has started to sail).
To understand the data, it is critical to remember that hospitalizations reflect the spread of the coronavirus several days earlier. The medical literature and my earlier modeling work suggest that most hospitalizations occur seven to 11 days after a person is infected, and nearly all occur within 15 days.
Given that California began reopening on May 8, we should see a strong downward trend in hospitalizations until roughly May 15 to May 19. From that point forward, with a modest increase in the rate of spread, we should expect to see a much slower decline in hospitalizations, potentially followed by a leveling out or very gradual increase in hospitalizations as we expand our reopening.
As the chart below demonstrates, this is essentially what occurred during the first several weeks of our reopening. The steep decline in hospitalizations ended on May 16 — eight days after California reopened.
From May 16 until June 16, daily hospitalization levels hovered around 4,500 — consistent with numbers from earlier in May and well below our peak of approximately 5,800 on April 7.
Over the past two weeks, however, daily hospitalization levels have risen substantially and far more than we would have hoped. Why?
To correctly interpret the hospitalization data over the past two weeks, we need to take a much closer look at the data over the past seven weeks and how it corresponds to different phases of the reopening.
Phase 1
Hospitalizations rose initially, but then slowly declined from May 16 to May 30. This suggests that the coronavirus continued to contract, albeit more slowly, during the initial phase of the statewide reopening, which lasted until roughly May 18 through May 22.
During this latter five-day window, many populous counties completed their attestation processes and began rapidly reopening more of their economies.
Phase 2
The increase in attestations on the eve of Memorial Day weekend, combined with another reopening round the following week, likely explains the subsequent rise in hospitalizations that began on June 1 and continued until June 8. But hospitalizations then declined for five days.
Interestingly, this rise and fall in hospitalizations suggests this may be pattern associated with major reopening rounds, particularly if they occur on Fridays and spur greater social interaction over the ensuing weekend.
Indeed, my modeling strongly suggests there is such a pattern in the data going back to the beginning of May: Fridays through Sundays generate significantly more future hospitalizations than Mondays through Thursdays.
The massive protests over the death of George Floyd from May 29 to May 31 appear to have had little or no impact on the spread of COVID-19. There was a miniscule increase in hospitalizations from June 6 to June 8.
Phase 3
However, later rounds of the protests on June 6 and 7 likely contributed to the rise in hospitalizations that began on June 14.
Phase 4
On June 12, there was a substantial round of reopening throughout California, which included hotels (for tourism), bars, wineries, gyms and many other businesses. In addition, there were substantial Black Lives Matter protests on June 13 and 14.
The combination of these events likely caused the significant increase in the hospitalization rate that began on June 19 and reached its greatest rate of daily increase on June 21 and 22. My modeling supports this assessment.
Phase 5
With fewer protests since June 14, the increase in the hospitalization rate from June 23 to now is largely the result of the ongoing economic reopening that began on June 12.
The key question, therefore, is whether hospitalizations will flatten starting on June 24 and then decline as they have done with prior major reopening rounds. To date, the curve has not flattened nearly as much as it has after previous reopening rounds. This needs to be monitored carefully.
In addition, we do not yet know whether the statewide order to wear masks in public will have any discernable impact on hospitalizations. Any evidence of its impact should start appearing in the data between June 26 and June 30. Ultimately, by July 5, we should have a far more accurate understanding of the trajectory of the coronavirus.
What should we do while we wait to see the hospitalization data over the next week?
First, we should recognize that reopening has been largely successful. The reopening process had little impact on the trajectory of the coronavirus until June 6. This means that California can handle a substantial amount of economic and other activity without meaningfully increasing the spread of the virus. This is very good news.
Second, we should not push the panic button. Throughout California, we have ample hospital capacity even with the increases over the past two weeks (although I recognize certain counties are much closer to reaching baseline capacity and utilizing surge capacity). The state can, therefore, continue with our current level of reopening while it tracks new hospitalization data over the next week.
Third, we have plenty of time to make analytically sound public health decisions. If the hospitalization rate does not level off, we will still have several weeks before California will exceed its baseline hospital capacity.
Under this scenario, our public health professionals would have ample time to develop and implement narrowly tailored “snap-back” orders that further protect the most vulnerable and alter the activities most likely driving the growth of the coronavirus.
In this regard, the mask order stands as a sensible and minimally disruptive measure to slow the spread of the virus without altering the course of our reopening.
By contrast, it is hardly clear that Newsom needed to close bars in several counties this week. And although it is a fairly narrow response to the increased rate of transmission, it is also unclear whether there is any analysis to support the view that such closures will meaningfully reduce hospitalizations, given the likely differences in the demographics of bar patrons and many of those most at risk for hospitalization from COVID-19.
It is clear, however, that we do not need to return to anything close to a full stay-at-home order under any foreseeable circumstances. Our experience from May 8 to June 6 proves this would be unnecessary to control the spread of the coronavirus.
Fourth, please be prudent and protect yourself and others when in public. Living with COVID-19 today does not mean returning to the way things were last November.
We still must take measures to ensure the virus does not spread at a rate that would overwhelm our health-care system.
— Brian Goebel served as a senior official in the Treasury and Homeland Security departments following 9/11. Since 2005, he has founded successful consulting and analytics firms serving governments around the globe; launched 2040 Matters, a nonpartisan public policy blog dedicated to restoring the American Dream for younger Americans; and was elected to the Montecito Water District Board of Directors in 2018. Click here for previous columns. The opinions expressed are his own.