At the peak of Covid-19 age and disease severity but not comorbidities are predictors of mortality. Covid-19 burden in Bergamo, Italy

Background. Findings from February, 2020, indicate that the clinical spectrum of Covid-19 can be heterogeneous, probably due to theinfectious dose andviral load of SARS-CoV-2 within the first weeks of the outbreak.The aim of this study was to investigate predictors of overall 28-day mortality at the peak of the Italian outbreak. Methods. Retrospective observational study of all Covid-19 patients admitted to the main hospital of Bergamo, from February 23 to March, 14, 2020.Results. 508 patients were hospitalized ,predominantly male (72.4%), mean age of 66±15 years; 49.2% were older than 70 years. Most of patients presented with severe respiratory failure (median value [IQR] of PaO2/FiO2233 [149-281]). Mortalityrate at 28 days resulted of 33.7%(N=171).39.0% of patients were treated with continuous positive airway pressure(CPAP), 9.5%with non-invasive ventilation (NIV)and 13.6% with endotracheal intubation. 9.5%were admitted to semi-intensive respiratory care unit, and 18.9%to ICU. Risk factors independently associated with 28-day mortality were advanced age (≥78 years: odds ratio, OR, 95% confidence interval [CI] 38.91 [10.67-141.93], p<0.001; 70-77 years: 17.30 [5.40-55.38], p<0.001;60-69 years: 3.20 [1.00-10.20], p=0.049), PaO2/FiO2 <200 at presentation (3.50 [1.70-7.20], p=0.001), need for CPAP/NIVin the first 24 hours (8.38 [3.63-19.35], p <0.001), and blood urea valueat admission (1.01 [1.00-1.02], p=0.015). Conclusions. At the peak of the outbreak, with a probable high infectious dose and viral load, older age,the severity of respiratory failure and renal impairment at presentation,but not comorbidities,are predictors of 28-day mortalityin Covid-19.