Illustration of the seasonal flu virus. There are 3 types of virus that all have a nearly identical morphology : Type A and B viruses have 2 types of envelope glycoproteins or viral surface proteins (Neuraminidase et hemagglutinin). Type C virus doesn抰 have surface Neuraminidase. The lipid bilayer is visible, then the internal part of the envelope made up of M proteins. In the centre, in green, is the ribonucleoprotein (RNP).