IL6 and Lassa fever: IL-6 is highly upregulated in fatally infected NHPs and in LASV-infected humans, and elevated levels of IL-6 in plasma is currently being considered as a third biological marker of lethal Lassa fever in addition to viremia (>3.3 logs/mL) and liver enzyme aspartate aminotransferase (AST) (150 IU/mL) [25].