However a virus is a delivery device that precisely codes elements for self-replication, for structural form, and for pathogenesis. This last is the intrinsic d

However a virus is a delivery device that precisely codes elements for self-replication, for structural form, and for pathogenesis. This last is the intrinsic disease causing component, though exactly how badly the interaction goes for an individual is dependent on the context of their immune system and general physiology. Apparently the 1918 H1N1 influenza virus had a particularly nasty pathogenic component, that mercifully has not been seen in the typical seasonal flu.