Up to 20% of the U.S. population will develop influenza each year. Influenza causes significant illness and death, especially in vulnerable populations such as infants, elderly, and immunocompromised persons. In April 2009 local healthcare providers, state health departments, and the CDC responded to influenza caused by a new virus (2009 Novel H1N1), first identified in Mexico. A pandemic was declared by the World Health Organization (WHO) in June 2009, the first since 1968. Unlike seasonal influenza, the groups at high risk for severe illness due to H1N1 virus included otherwise healthy children over the age of 2 years. In the U.S., the pandemic virus caused a substantial rise in influenza activity. The WHO declared the pandemic over in August 2010; however, the 2009 H1N1 virus is expected to circulate as one of several influenza strains during the 2010-1011 flu season.
Community healthcare providers including pharmacists and nurses play a key role in symptom recognition, patient triage, and provision of drug information, medications, vaccines and education. This article will review characteristics of influenza, including viral evolution, signs and symptoms of infection, subsequent complications, diagnosis, and the approach to management.