Analysis: COVID-19 in Miami-Dade

With Mayor Carlos Giménez beginning to tighten the screws on Miami-Dade residents and businesses again it’s worth analyzing the COVID-19 statistics closely, more closely than you’ll find in the local fishwrap. All of the data you’ll see here is from the county’s daily dashboards that they’ve been publishing for the last couple of months.

Around the country we’re being told that there’s a “second wave” of infection occurring. This narrative is based on an explosion of positive tests, also called new cases. But positive tests are a flawed statistic for many reasons. The first is that the number of positive tests can be largely driven by how much testing is going on. The availability of tests and the demand for them has varied greatly over the course of the four months of the pandemic. Generally, a lot more testing is going on now than in March and April. Additionally, a positive test isn’t the same thing as someone who is sick. We’ve observed that a great proportion of cases are asymptomatic or mildly symptomatic. Another thing to consider is that we don’t even know yet how accurate these tests are. Every test has false positives and false negatives. The more tests that are administered, the better the handle experts will have on the accuracy of the tests, but that’s an academic exercise that we may not know the answer to for some time. Still, even with the flaws, it’s good to get grounded on what’s happening with positive tests or new cases.


In the chart above you’ll observe the blue bars which represent number of “New Positive Cases” by day, according to the county. The red line is the 7-day rolling average. The reason for the average is to smooth out inconsistencies due to reporting lags. On June 4th, the rolling average of new cases hit its low at about 140. As of today, that average is about 1,980. That means today we have roughly 14x the number of new cases being reported daily than we did a month ago.


Next, I want to demonstrate what’s going on with the percentage of tests that are positive. As you can see, the red line of the 7-day average indicates that up until about the 17th of June that percentage was consistently under 10, slowly rising from its lowest point, which was about 5% on May 26th. And now suddenly we’re routinely seeing positivity in the 20s. An unexplained 3-day spike in May and the sudden surge in positivity make me wonder about the accuracy of the tests and the labs that are evaluating them.


Now that we’ve discussed positive tests, both in absolute numbers and as a percentage of total tests, it’s time to move on to what I believe are the more meaningful statistics of hospitalizations, ICU occupancy and ventilator usage. Remember, the whole “flatten the curve” strategy was sold to us as a way to ensure that medical resources weren’t overwhelmed. Nobody promised that we were going to eradicate the virus or save lives, except for those lives that might be lost for lack of resources.

In the chart above, the blue line indicates the number of hospitalized COVID-19 patients in the county. The curve was flat for about 6 weeks with about 600 COVID-19 patients being hospitalized at any given time. The low point was June 11th when there were 553 such patients in county hospitals. Then we see an upswing, and as of today there are 1,657 COVID patients. From the low of 553 to today we’ve seen a 3x increase in hospitalizations. This is a large increase, no doubt but a far cry from the 14x increase we saw in terms of positive tests. But, to be fair, hospitalizations lag positive tests as it takes some time for the disease to develop to the point where someone requires care in a hospital. Note however that Miami-Dade has a total of 8,575 hospital beds, most of which are not being used by COVID patients, and as of today 22% were available.

What’s more interesting to me is the change in the number of patients requiring ICU depicted on the yellow curve. On May 6th, there were 136 COVID patients in ICU and the curve gradually decreased until it hit a low of 83 on June 1st. As of today, the number is 331, which is a 4x increase from the low. Again, substantial but nowhere near the increase in positivity. Note that the county has 988 adult ICU beds and as of today 19% were available.

Lastly is the number of patients on ventilators, represented by the gray line. That number reached its low on June 1st when there were 47 COVID-19 patients on ventilators. Remember, in the beginning, policy makers expressed grave concern about having enough ventilators to meet the demand. Fortunately, doctors have learned a lot about COVID-19 and some of the biggest breakthroughs have been regarding ventilator protocols. Doctors are not as trigger happy to intubate COVID patients and put them on ventilators since they noticed an abnormally high mortality among such patients when compared to other Acute Respiratory Distress Syndrome (ARDS) patients. Other therapies (high levels of oxygen and proning) are being used to avoid getting to a stage where the patient requires a ventilator. In any case, the number of patients on ventilators in the county is 168 as of today, a 3.6x increase since the low on June 1st.


The chart above demonstrates countywide COVID deaths. You’ll notice that the deadliest day of the observed record was May 6th, when 23 people died of COVID. The curve gradually settled to about 8 deaths a day. That has risen to about 12 deaths a day. NOTE: deaths take some time to report accurately so the deaths at the end of the data set are almost certainly incomplete.


Based on everything reported above, I believe we are having a “second wave” of infection but that the extent of that second wave is being exaggerated by a rise in positive tests that, at least to date, is disproportionate to the number of hospitalizations, ICU occupancy and ventilator usage. I believe the high number of positives are probably the result of changes in test accuracy (faulty tests early on in the pandemic may have resulted more false negatives than reality or faulty tests combined with much more testing now may be resulting in far more false positives than reality).

In any case, we’ve had some significant but not yet alarming increases in hospitalizations, ICU occupancy and ventilator usage while deaths continue to be relatively flat. I believe this demonstrates that while there are more COVID-19 hospitalizations, the preponderance are less severe than at the beginning of the pandemic, as the proportion of hospitalized patients in ICU is at 20%, lower than 23% in early May. Likewise, the proportion of hospitalized patients on ventilators is is at 10%, lower than the 14% we were seeing in early May.

Given that there is no vaccine for COVID-19, and none on the immediate horizon, people are going to be infected. It’s not a matter of if, it’s a matter of when. That means our goals should be based on what we were originally sold as the benefits to flattening the curve, which is to ensure medical resources aren’t overwhelmed.

It’s entirely possible that this “second wave” is actually a postponed first wave, and that the problem was that we shut everything down too early and not enough people were previously exposed to the virus to give us critical mass and the bell curve with a downward slope we were all hoping for.

I strongly oppose returning to an enforced lockdown as Mayor Giménez is dictating because of all the negative effects we’ve seen already. We need to learn to live with COVID-19 in our midst. People are going to get sick and some are going to die, but without a cure or vaccine the question is how long do we want to prolong this agony and at what expense?

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