Influenza is the name of a family of Viruses that cause all forms of flu ranging from Seasonal Flu to Bird Flu. The simple makeup of a virus molecule makes it fast at adapting to its environment, making them notoriously hard to treat in some cases. It is still up for debate as to whether viruses are technically thought of as ‘alive’.
The influenza virus is a spherical capsid containing an RNA genome. The capsid is enclosed by a lipid bilayer membrane. This membrane features two membrane-bound protein, neuraminidase and haemaglutinin. The haemaglutinin protein allows the virus to adhere to cell surface proteins in order to invade, whilst the neuraminidase proteins cleave these adhesive points from infected cells to prevent new virus particles from reinvading the same cell. There are several distinct versions of each of these proteins which allow strains of influenza to be classified, such as H1N1.