Fig. 1

Selection of severe acute respiratory infection (SARI) samples from a larger retrospective ‘case-series’ of the 2016–2017 SARI hospitalized population using a case–control sampling approach. SARI patients were categorized in two groups: a cases, defined as SARI patients with a severe influenza infection based on the presence of at least one severe complication, i.e. stay in intensive care unit (ICU), acute respiratory distress syndrome (ARDS), extracorporeal membrane oxygenation (ECMO), invasive respiratory support, and death, and b controls, defined as SARI patients without one of these severe complications. Cq (quantification cycle) = relative measure of the concentration of target in the PCR reaction