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(A) Schematic images showing different portal entry of viruses through nose, throat and lungs. Respiratory viruses are commonly spread through inhaling the virus particles containing droplets (B) Influenza subtype profile in global influenza types in circulation in the order high to low number of incidence occurred with influenza A and B followed by subtypes, H1N1, H3 and B-Yamagata that are derived from influenza A [9].
