The determinants of the changing speed of spread of COVID-19 across Italy

Abstract

The COVID-19 epidemic showed inter-regional differences in Italy.We used an ecological study design and publicly available data to compare the basic reproduction number (R0), the doubling time of the infection (DT) and the COVID-19 cumulative incidence (CI), death rate, case fatality rate (CFR) and time lag to slow down up to a 50-days doubling time in the first and the second 2020 epidemic waves (δDT50) by region.We also explored socio-economic, environmental and lifestyle variables with multiple regression analysis.COVID-19 CI and CFR changed in opposite directions in the second vs.the first wave: the CI increased sixfold with no evidence of a relationship with the testing rate; the CFR decreased in the regions where it was initially higher but increased where it was lower.The R0 did not change; the initially mildly affected regions, but not those where the first wave had most severely hit, showed a greater δDT50 amplitude.Vehicular traffic, average temperature, population density, average income, education and household size showed a correlation with COVID-19 outcomes.The deadly experience in the first epidemic wave and the varying preparedness of the local health systems might have contributed to the inter-regional differences in the second COVID-19 epidemic wave.