Florida: Summer Analysis Update

Younger Cohort Activity is Driving the Florida Second Wave

In Florida there was abundant activity in June, largely among a younger cohort (20 to 50 year olds), and this caused a significant second infection wave.  This wave will likely damp down and eventually die off.  School age children have an insignificant effect on the overall death rate.  Elderly people are at risk and should continue to protect themselves from exposure.

This analysis replaces the study from early July: Florida: Second Wave Analysis.  The Florida second wave has been more intense than our original analysis anticipated due to high connectivity in the month of June.  Delays and ambiguities in Florida data make it difficult to establish a calibration baseline with proper timing and magnitudes.  We have improved our calibration approach and algorithms to better match the data trends.

Updated Recovery Models

We examine 4 recovery models which reflect the likely range of outcomes for Florida.  All cases reflect dynamic age balanced mobility and social distancing (connectivity).

  • Case 1: Active June, July slowing, risk balanced Fall, schools open, elderly distance, vulnerable protected
  • Case 2: Same as Case 1 with slower transition to July reset.
  • Case 3: Same as Case 1 with faster return in August, more active elderly
  • Case 4: Active June and July, with faster return in August, more active elderly

Analysis Observations

  • Florida residents are generally modulating their behavior in proportion to risk
  • 20% of Florida residents have been infected by late July.
  • Overall 30% of Florida residents will be infected by next year, comparable to NYC.
  • Infection rates are very high among younger individuals in the 20 to 50 age range.
  • Total deaths will be in the range of 600/million (compare to NYC ~2,800/million, Sweden ~750/million)
  • Death rates continue to be heavily tilted to elderly populations.
  • Returning children to school and extracurricular activities do not cause a significant increase in deaths or infections.
  • Risk proportional mobility lowers herd immunity; reached when 30-40% of 20-50 year olds are infected.
  • Vulnerable and elderly populations are at risk and should continue to take precautions and avoid high risk situations.
  • The second infection wave will eventually die out, we will not see a third wave infection peak.
  • A third wave of deaths is possible if elderly people loosen up too early, but this will not drive the infection vectors for the general population.

Death Trends

Case 1 and Case 2 are similar, with slightly more deaths in Case 2 as expected.  Case 3 and 4 have second waves of deaths in October, two months after the increase in activity in elderly populations.  The take away is that until the infection has damped down, elderly and vulnerable people should continue to avoid risky situations and practice social distancing.  We do see the infection dying out if people continue to manage their connectivity in proportion to their risks.

 

Susceptible Infected Deaths and Recovered (SIRD) Summaries

Infection Trends

In general we see the peak of new infections for Case 1 and 2 in late June.  For the more aggressive recovery model, we see infections peaking in early July for Case 3 and mid July for Case 4.  The percentage of the population currently infected shows a peak a couple weeks after the peak of new infections.  With the delay from infection to test, and from test to results, we would expect to see the peak of positive tests to be later in July.  As the average age of infection shifts to the lower mortality rate cohorts, we see the infection fatality rate drop to ~0.2%.  As older people become more mobile in Case 3 and 4, we see the infection fatality rate rise to ~0.4% later in the year.

Distribution of Infections and Deaths by Age

The graphs below are the cumulative distributions at the end of the analysis run. Blue is the normalized general population age distribution. Red is the cumulative normalized percentage of overall infections. Green is the cumulative normalized percentage of deaths from COVID-19.

Infection Rate, Infection Fatality Rate and Death Rate by Age

Below are the final population infection rates (percentage of population infected), the infection fatality rates (percentage of those infected who die) and the overall population death rates (the percentage of deaths relative to population) for each age bin.

 

Dynamic Connectivity Inputs

In all cases school age children return to full connectivity in the fall.  20 to 60 year olds largely return to normal with common sense social distancing and 60-70 year olds partially return to normal.  Case 1 has a rapid reaction to rising infections in late June and Case 2 has a slower reaction, otherwise they are the same.  Case 3 has an overall more aggressive return to normal with mild social distancing for 60 and under and a partial return to normal for those over 70 and over.  Case 4 is a very aggressive return to normal, with mild social distancing for younger people and moderate social distancing for those 60 and over.  In all cases special protection is afforded to the vulnerable.

 

Date of Death Extraction

Determination of actual date of death is critical to calibration of the analysis.   The graph below shows the derived date of death the reported death date data sets found at the COVID Tracking Project.  Our approach is far more accurate than a rolling average of reported deaths and is detailed here: Reported versus Actual Date of Death.   The most recent week represents an incomplete count.

Late July Infection Status Distribution

The distributions in this model by age closely match the actual data found here: Florida COVID Report.

Conclusion

Florida is likely to have total deaths in the range of 10,000 to 15,000 depending on the behavior of elderly individuals.  There is little risk of children returning to school and younger cohorts returning to reasonable levels of activity with age appropriate risk management.  It is clear from our analysis that those at risk need to continue to take abundant precautions and they should be reminded to do so by public health officials.  Those who live in care facilities should be protected with strict safety measures.  Schools can reopen with little overall effect, however at risk teachers should be afforded extra accommodations to manage their exposure.  Middle-aged adults should re-engage but do so with reasonable precautions to prevent the spread to older and more vulnerable populations.  This measured approach will allow us to safely recover our economy and get back to normal.

Summary Outcome Tables

Cumulative Infections and Deaths by Age Bin Sand Charts

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