Seasonal influenza is an acute respiratory infection caused by influenza viruses which circulate in all parts of the world. There are 3 types of seasonal influenza viruses, types A, B, and C. Influenza type A viruses are further classified into subtypes according to the combinations of 2 different proteins, the haemagglutinin (H) and the neuraminidase (N), located on the surface of the virus. The subtypes of influenza A viruses currently circulating among humans are influenza A (H1N1) and A (H3N2) subtypes.
The circulating influenza A (H1N1) is also written as A (H1N1) pdm09 as it caused the pandemic in 2009 and subsequently replaced the seasonal influenza A (H1N1) virus which had circulated prior to 2009. Only influenza type A viruses are known to have caused pandemics. Circulating influenza B viruses can be divided into two main groups (lineages), referred to as B/Yamagata and…
