Bergamo Italy 57% Exposure Rate Analysis

Let's look at special case high density outbreak, like the Bergamo region of northen Italy, approximately 1 million people.  Here we see an elderly demographic, high connectivity culture and a high seed rate via the Wuhan province worker connection.  These conditions presents a perfect storm for a rapid high penetration COVID-19 outbreak, even worse than that in New York City.
Antibody testing in the Bergamo region shows approximate 57% of the population was exposed: Coronavirus: Tests show half of people in Italy's Bergamo have antibodies
Mortality is likely higher than reported in the Bergamo region as detailed in this paper estimating over 6,000 deaths: How deadly is COVID-19? A rigorous analysis of excess mortality and age-dependent fatality rates in Italy

Analysis of the Bergamo Outbreak

We have completed an analysis of the Bergamo region outbreak using the Covid Decision Model and account for these regional factors as inputs to the analysis:

  • elderly age demographic representative of the region.
  • a severe seed rate for Wuhan workers early in the year.
  • high connectivity population.
  • standard outcome distributions based on latest data with sloped asymptomatic versus age (about 50% overall).
  • representative lockdown profile.

If antibody testing shows 57% exposure then we would calculate IFR of 6,000 / 570,000 = .01 or 1%. Our analysis results show that overall 60% of the population become infected mid summer as the last vestiges of the disease die out with an IFR of 1.11%. Our simulation population of 100k scaled by 10.

Summary Results for Bergamo Analysis
Bergamo SIRD Running Tally's
Bergamo Daily Deaths

Bergamo Second Wave Risk Analysis

If Bergamo returned to normal, would there be any resurgence?  Our analysis is consistent with this data and shows that with minor shifts in behavior and protecting the vulnerable, there is little risk of resurgence. Below are is an analysis with the same starting conditions, followed by a complete return with only vulnerable people protected (light-switch rebound). Even with light-switch rebound, disease dies out in July after a minor blip.
Bergamo Light Switch Transient Parameters
Bergamo Light Switch R(t)

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