[citation needed] The enzyme helps viruses to be released after budding from the plasma membrane of a host cell.

While the hemagglutinin on the surface of the virion is needed for infection, its presence inhibits release of the particle after budding.

Viral neuraminidase cleaves terminal sialic acid residues from glycan structures on the surface of the infected cell.

[medical citation needed] Neuraminidase has been targeted in structure-based enzyme inhibitor design programmes that have resulted in the production of two drugs, zanamivir (Relenza) and oseltamivir (Tamiflu).

[citation needed] On February 27, 2005, a 14-year-old Vietnamese girl was documented to be carrying an H5N1 influenza virus strain that was resistant to the drug oseltamivir.

In growing fears of a global avian flu pandemic, scientists began to look for a cause of resistance to the Tamiflu medication.

[citation needed] A new class of neuraminidase inhibitors that covalently attach to the enzyme have shown activity against drug-resistant virus in vitro.