Respiratory virus surveillance. FluWatch project, 2000-2001. End of season update

The 2000-2001 season was a relatively mild season worldwide. In Canada, lower than usual activity was reported for all national indicators of influenza activity, including the rate of influenza-like illness (ILI), the percentage of laboratory-confirmed cases of influenza and provincial/territorial influenza activity levels. However, there were a number of interesting characteristics of this year's influenza season. In contrast to the predominance of influenza A, and in particular the A/Sydney/5/97 (H3N2)-like virus over the past 3 years, influenza B predominated overall this season. Influenza A (H3N2) accounted for < 1% of all characterized isolates (H1N1 accounted for 49% of isolates). Increased laboratory-confirmed influenza activity began in the West (Yukon, prairie provinces and British Columbia) in mid-December, followed by the Atlantic provinces in mid- to late January and Ontario and Quebec in mid- February and March.