Kallas EG, et al. - A cohort of patients admitted to hospital during the 2018 outbreak of yellow fever in the outskirts of São Paulo city, Brazil, was studied to determine the predictors of death measured at hospital admission in these patients. From the first 15 viral load-detectable samples, 14 complete yellow fever virus genomes were generated that belonged to a single monophyletic clade of the South America I genotype, sub-genotype E. Researchers noted higher mortality in correlation to older age, male sex, higher leukocyte and neutrophil counts, higher alanine aminotransferase, aspartate transaminase (AST), bilirubin, and creatinine, prolonged prothrombin time, and higher yellow fever virus RNA plasma viral load. The multivariate regression model suggested a continuous independent association of older age, elevated neutrophil count, increased AST, and higher viral load with death. These findings establish the important role of the virus in disease pathogenesis, indicating the value of an effective antiviral that could alter the clinical course for patients with the most severe forms of yellow fever.