Non-seasonal influenza infections have specific clinical manifestations. Pneumonia related to the 2009 H1N1 influenza A pandemic was also found in many cases to be rapidly progressive, leading to respiratory failure and ARDS [20•, 21•] . Additionally, the risk for complications and death due to that (2) Including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, seizure disorders, stroke, intellectual disability, moderate to severe developmental delay, muscular dystrophy, or spinal cord injury Adapted from the recommendations of the Advisory Committee on Immunization Practices (ACIP) [40••] pandemic influenza was found to be underestimated by commonly used pneumonia severity scores [22•, 23] . Avian influenza (H5N1) frequently presents as severe primary pneumonia that often progresses rapidly to the acute respiratory distress syndrome (ARDS), having caused high rates of death, especially among infants and young children in Southeast Asian countries [24] .