Is the rise and fall of COVID in Florida “inexplicable”?



At a joint meeting of the Gainesville City Commission and Alachua County Commission on August 25, Dr. Michael Lauzardo, Chief and Assistant Professor of the Division of Infectious Diseases and Global Medicine at UF, said, “We’re in a little bit better spot than we anticipated with the epidemic when we saw the numbers go up in the mid-summer… What’s been going on in the county and going on on campus is pretty much reflective of what’s going on throughout the state and in most of the sun belt states. Our cases peaked in about the second to third week of July, and that was reflected not only in the number of cases in the county, but also in the number of patients that we were seeing in the hospital… In addition, we have seen the people modify their behavior. The use of masks, we believe, is what’s resulted in cases dropping inexplicably, and they have been able to go down.”

In response to an emailed question, he clarified that when people hear that reported cases are increasing, they go out less and wear masks more often.

So the hypothesis is that when cases started going up, people were more compliant about mask-wearing and also decreased their activity. Is there any evidence for this?

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We used CDC charts that superimpose COVID case counts on mobility data. All types of mobility fell sharply in mid-March, reaching the lowest levels in April. Mobility everywhere then began a steady climb until early July. In Alachua County and Florida, cases were flat or declining until mid-June, when the sunbelt states all started reporting higher cases. In the U.S. as a whole, cases actually declined while mobility increased.

Other than brief downward spikes for the July 4 holidays, mobility in Alachua County stayed nearly flat throughout the increase and decrease in COVID cases in July and early August. Florida saw a very slight decrease in mobility in July and August, but there is no statistically-significant relationship between cases and mobility in Alachua County, in Florida, or in the U.S. as a whole.

So changes in mobility do not explain either the rise or fall in cases. What about masks? 

Alachua County implemented a face mask mandate on May 4 and has not removed it at any point. Enforcement has been increased several times, but the county’s data shows high compliance since they started measuring it on July 3. In spite of no change in mask policies, cases in Alachua County began rising in mid-June, plateaued through July and early August, then began dropping.

You can also see that the Phase 2 reopening, often blamed for the mid-June increase in cases, did not result in any increase in mobility.

Miami-Dade implemented a mask mandate on April 9 and added an outdoor face mask mandate on July 2. They had a massive spike in cases in July without changing any policies at all, and the cases began declining in August. Miami remains in Partial Phase 1.

A New York Times survey on mask usage found in early July that 75% of people in Alachua County say they always wear masks, and another 17% frequently wear masks. Miami-Dade is similar: 75.6% say they always wear masks, and another 12.8% frequently wear masks. 

Unfortunately, there is no data on mask compliance from before the mid-June spike, but there is no evidence for the claim that more people started wearing masks when case numbers increased. It is clear from the charts that face mask mandates alone don’t have any predictive value in explaining increases or decreases in cases. 

This tool uses the New York Times mask survey data to place every county in the United States on a graph with the percentage of people who always or frequently wear masks vs. cases or deaths in that county. To use it, ignore the sliders at the top right of the page, de-select TN from the list of states, then select FL. On the cases tab, it appears that there is a correlation between increased mask use and decreased cases, but if you hover over the line, you’ll see that the R-squared value is 0.18, indicating that the frequency of mask use does not explain the number of cases. 

If you select the deaths tab, you can see that there is no relationship at all between mask use and deaths per 100k population in Florida.

What’s inexplicable is that Lauzardo doesn’t seem to be familiar with Farr’s Law: “Farr showed that epidemics rise and fall in roughly a bell-shaped curve (a normal distribution) shape.”

The graph below shows the rise and fall of cases and deaths in Florida. The death curve is so small that the second graph makes it 10 times bigger so you can see it. The dotted area for deaths shows the deaths that have been reported so far, but deaths reported in future weeks will fill in the dotted section.

The graph of Florida’s cases and deaths looks very similar to Farr’s law, right down to the ~21-day lag between the peaks in cases and deaths, making normal behavior of viruses a more likely explanation for the rise and fall of cases/deaths than the behavior of the population.

Dr. Lauzardo and our local politicians seem to feel that they have to do something to defeat the pandemic, and worse, we must all be forced to do the things they have decided are necessary, even if there’s no evidence that they do anything at all. The downsides of their mandates, including closed businesses, suicides, overdoses, domestic abuse, and missed medical care, are never mentioned except when local governments have federal CARES Act money to hand out to victims of their policies.