感染症と治療ジャーナル

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Italian Mortality Time Series Underline Hidden Dynamics that Reveal Unexpected Links between COVID-19 Epidemic and North-South Divide

Stefano Dumontet, Alessandro Giuliani, Giovanni De Falco, Valeria Fedeli, Mariano Bizzarri

The temporal correlation structure between the profiles of all-causes mortality relative to Italian regions highlighted a largely, unexpected result. Notwithstanding the elimination of well-known seasonal effects, the time series of fluctuations in death rates with respect to the 2015-2019, showed a very high mutual correlation among the 20 Italian regions under scrutiny, ruling out any ‘randomness’ hypothesis. On the contrary, the standardized death rates dynamics was almost invariant along the years, giving rise to a major ‘size’ principal component correspondent to the among regions shared motion, and a second ‘shape’ component modelling the North-South antiphase behaviour. The COVID-19 epidemic, while affecting the breadth of mortality incidence, did not change the among regions correlation dynamics, thus suggesting that this contingency impinges on an intrinsic death rate dynamical mode. The exceptional increase in mortality in the Northern regions observed in 2020 was of the same entity of the North-South differences in mortality observed in ‘normal’ periods. A coherent and homogeneous distribution of mortality rates would had be expected if COVID-related death were to be attributed (solely) to the pathogenic potency of the virus. Conversely, differences in mortality trends across the North-South divide may likely reflect differences in health care availability or other societal features.