Alert Characteristics.

Notes1 After accounting for a 2 week operational delay. In 12 out the 28 regional seasons, the alert should have been available at least 3 weeks before the peak in influenza hospitalizations.2 A novel strain (A⁄Fujian⁄411⁄02) emerged in the 2003/04 season and dominated the season. Prompt alerts that are provided before the peak are more crucial in seasons when a single strain dominates. The alert period will be shorter when a single strain circulates.Alert Characteristics.