title: Update: influenza activity--United States and worldwide, May-September 2003.
abstract: During May-September 2003, influenza A(H3N2) viruses circulated worldwide and were associated with mild to moderate levels of disease activity. Influenza A(H1) and B viruses were reported less frequently. In North America, isolates of influenza A(H3N2), A(H1), and B were identified sporadically. This report summarizes influenza activity in the United States and worldwide during May-September 2003. Influenza activity in North America typically peaks during December-March, which underscores the need to begin vaccinating against influenza in October and to continue vaccination into December and throughout the influenza season.
mesh_terms: D014943:Global Health; D006801:Humans; D009980:Influenza A virus / Q000302:isolation & purification; D009981:Influenza B virus / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology