Neuraminidase enzyme. Molecular model of the viral enzyme neuraminidase. In the background is a coloured transmission electron micrograph (TEM) of an influenza (flu) virus (blue/black). Neuraminid- ase is found on the surface of influenza viruses, and is essential for the spread of viruses through the body. Atoms are represented as spheres, and are colour-coded: carbon (green), nitrogen (yellow) and oxygen (blue). Neuraminidase's purpose is to allow new viruses to exit the cell in which they were created. New drugs which have been specifically designed to block neuraminidase have been found to dramatically reduce the duration of the symptoms of influenza.