Data from the COVID-19 epidemic in Florida suggest that younger cohorts have been transmitting their infections to less socially mobile older adults.

Jeffrey E Harris

doi:10.1007/s11150-020-09496-w

Abstract

We analyzed the daily incidence of newly reported COVID-19 cases among adults aged 20–39 years, 40–59 years, and 60 or more years in the sixteen most populous counties of the state of Florida from March 1 through June 27, 2020. In all 16 counties, an increase in reported COVID-19 case incidence was observed in all three age groups soon after the governor-ordered Full Phase 1 reopening went into effect. Trends in social mobility, but not trends in testing, track case incidence. Data on hospitalization do not support the hypothesis that the observed increase in case incidence was merely the result of liberalization of testing criteria. Parameter estimates from a parsimonious two-group heterogeneous SIR model strongly support the hypothesis that younger persons, having first acquired their infections through increasing social contact with their peers, then transmitted their infections to older, less socially mobile individuals. Without such cross-infection, an isolated epidemic among older people in Florida would be unsustainable.

Highlights

Recent reports suggest that the age distribution of new cases of COVID-19 in the United States has shifted toward younger adults (Malmgren et al 2020)
The basic data on confirmed COVID-19 cases was derived from a regime of partial, voluntary testing
Recent estimates from serologic surveys suggest that, at least in the period before the Full Phase 1 reopening, the actual incidence of infection was significantly higher (Havers et al 2020) the available evidence from this detailed study in the 16 most populous counties in Florida points to a substantial rise in case incidence in both younger and older adults after Full Phase 1 reopening went into effect on May 18

Summary

Introduction

Recent reports suggest that the age distribution of new cases of COVID-19 in the United States has shifted toward younger adults (Malmgren et al 2020). One possible explanation is that younger adults have tended to adhere less strictly to recommended social distancing measures, especially as many states, counties and. A particular concern is that the higher prevalence of active infection among younger individuals will result in a higher rate of cross-infection in older persons. We use publicly available data on confirmed individual COVID-19 cases compiled by the state of Florida to test whether the incidence of new coronavirus infections has been rising more rapidly among younger cohorts. We explore whether the available data can be used to assess whether cross-infection of older cohorts is already occurring

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Conclusion