Contrary to what is commonly assumed, the influenza virus subtype does not seem to be a major determinant of clinical presentation and severity of influenza illness based on data from the last twenty years (Paget, 2018). On this particular subject, The Economist (Science & Technology 9 May 2020) wrote a piece which looked at the clinical manifestations of Covid-19 and compared them to influenza.
The piece in The Economist notes: 'A review of influenza papers published in 2018 by John Paget of Nivel showed that even when all of the different influenza types (A or B), and subtypes (H1N1, H3N2, etc.) were analysed, there were few differences in the ways they presented clinically. Literature on SARS-COV-2 suggests, by contrast, that this virus is a master of disguise and has a variety of clinical manifestations’. The article in The Economist is free to read.