Neuraminidase influenza enzyme. Computer artwork of a molecule of neuraminidase, an enzyme found on the surface of the influenza virus. Neuraminidase plays an important role in the pathogenicity of the virus; allowing the virus particles to exit the host cell after replication. There are nine known subtypes of neuraminidase, but only two of them (N1 and N2) have been linked to epidemics in humans. The influenza drugs tamiflu and relenza work by inhibiting neuraminidase.