The extensive spread of 2009 pandemic influenza A H1N1, also referred to as novel H1N1 2009 or swine flu, and the arrival of seasonal influenza present critical public health and clinical challenges. Key steps for the primary care physician are prevention efforts (e.g., vaccinating and educating patients about hygiene) and treatment of affected patients who are at high risk of influenza-related complications. The goal of medication therapy is not curative but rather to prevent severe illness and reduce the incidence of influenza-related complications for patients at highest risk. The 2009 H1N1 influenza virus has thus far been sensitive to the neuraminidase inhibitors oseltamivir (Tamiflu) and zanamivir (Relenza), with only rare oseltamivir resistance; however, it has complete resistance to adamantanes (rimantadine [Flumadine] and amantadine [Symmetrel]). Seasonal influenza, conversely, has a reverse sensitivity profile that is almost entirely resistant to oseltamivir and sensitive to adamantanes.

It will be important to track the influenza strains in individual communities to ensure proper management of persons at high risk for complications. The National HIV/AIDS Clinicians' Consultation Center (Warm-line) at the University of California San Francisco Department of Family and Community Medicine has developed an Influenza Management Guide (Online Tables A, B, and C). Initially, the guide was intended to address questions about treating influenza in persons with human immunodeficiency virus infection, but it became apparent that the guide is applicable to the care of all patients and would be useful to primary care physicians for prevention efforts and management of patients presenting with influenza-like illness. This guide is also available at http://www.nccc.ucsf.edu under the link “Influenza Management Guide.” It will be updated throughout the 2009–2010 influenza season to keep pace with the evolving epidemic.