Description
Transcriptional profiles are increasingly used to investigate the severity, subtype and pathogenesis of disease. We now describe whole blood RNA signatures and local and systemic immune mediator levels in a large cohort of adults hospitalised with influenza from which extensive clinical and investigational data was obtained. Signatures reflecting interferon-related antiviral pathways were common up to day 4 of symptoms in cases not requiring mechanical ventilatory support; in those needing mechanical ventilation, an inflammatory, activated neutrophil and cell stress/death (bacterial) pattern was seen, even early after disease onset. Identifiable bacterial co-infection was not necessary for this bacterial signature but could enhance its development while attenuating the early viral signature. Our findings emphasise the importance of timing and severity in the interpretation of transcriptomic profiles and soluble mediator levels, and identify specific patterns of immune activation that may enable the development of novel diagnostics and therapeutics