Influenza is a severe respiratory illness caused by either the influenza A or B virus that results in outbreaks of disease mainly during the winter months.
Currently approved antiviral treatments for influenza are partially effective and prone to viral resistance. Strains of flu virus that are resistant to approved treatments, osteltamivir (Tamiflu™) and zanamavir (Relenza™), have appeared and in some cases are predominant. For example, the predominant strain of the 2009 swine influenza pandemic was resistant to Tamiflu™.
These drugs target one of two viral proteins, hemagglutinin or neuraminidase, neither of which is highly conserved between viral strains. In fact, different influenza virus strains such as H1N1 and H5N1 are named by their respective differences in hemagglutinin (H) and neuraminidase (N) proteins. The ability of the influenza virus to produce viable variants of these two proteins is the key to its ability to develop resistance.
To learn more about influenza, please visit the information page at the Center for Disease Control and Prevention (CDC).