Alfonso Ilardi - MD, Department of Internal Medicine, A.O.R.N. "Antonio Cardarelli Hospital", Naples, Italy
Sergio Chieffi - PhD, Department of Experimental Medicine, University of Campania "Luigi Vanvitelli", Naples, Italy
Ciro Rosario Ilardi - MSc, Department of Psychology, University of Campania "Luigi Vanvitelli", Caserta, Italy

Background: This study aimed at assessing how population density (PD), aging index (AI), use ofpublic transport (URPT), and PM۱۰ concentration (PI) modulated the trajectory of the main COVID-۱۹ pandemic outcomes in Italy, also in the recrudescence phase of the epidemic.Study design: Ecological study.Methods: For each region, we recovered data about cases, deaths, and case fatality rate (CFR)recorded since both the beginning of the epidemic and September ۱, ۲۰۲۰. Data about totalhospitalizations were included as well.Results: PD correlated with, and was the best predictor of, total and partial cases, total and partialdeaths, and total hospitalizations. Moreover, URPT correlated with, and was the best predictor of,total CFR. Besides, PI correlated significantly with total and partial cases, total and partial deaths,and total hospitalizations.Conclusions: PD explains COVID-۱۹ morbidity, mortality, and severity while URPT is the bestpredictor of disease lethality. These findings should be interpreted with caution due to the ecologicalfallacy.

Air Pollution, COVID-۱۹, Ecological Study, Population Density, Public Transport