Pandemic influenza is defined as a new strain of influenza that spreads quickly globally. In Canada, among patients diagnosed with pandemic influenza (H1N1) from April 2009 to January 2010, 17% were admitted to intensive care unit (ICU), 10% needed mechanical ventilation, and 5% died in hospital. Antiviral agents are recommended for the treatment and chemoprophylaxis of pandemic influenza A(H1N1) and human avian influenza A(H5N1) by the Advisory Committee on Immunization Practices (ACIP) (January 2011). Amantadine and the neuraminidase inhibitors oseltamivir (Tamiflu, Roche) and zanamivir (Relenza, GlaxoSmithKline) are available in Canada for use as prophylaxis for and treatment of influenza. Oseltamivir is not approved for use in very young children (less than one year of age), and zanamivir is not approved for use in children under the age of seven years. Evaluation of the SDI (Surveillance Data, Inc.) electronic database in the US showed that the proportion of hospitalized patients who received antiviral treatment, comprising almost entirely neuraminidase inhibitors, increased from 34% in the 2006-2007 season to 70% during the 2009 H1N1 pandemic.