clinical aspects; comorbidity; complications; coronavirus disease 2019; elderly; human diseases; hypoxia; kidney diseases; kidneys; mortality; renal failure; risk factors; viral diseases; man; Severe acute respiratory syndrome coronavirus 2; Homo; Hominidae; primates; mammals; vertebrates; Chordata; animals; eukaryotes; Severe acute respiratory syndrome-related coronavirus; Betacoronavirus; Coronavirinae; Coronaviridae; Nidovirales; positive-sense ssRNA Viruses; ssRNA Viruses; RNA Viruses; viruses; acute kidney injury; clinical picture; aged; elderly people; older adults; senior citizens; kidney disorders; nephropathy; renal diseases; death rate; kidney failure; SARS-CoV-2; viral infections