a) Weekly number of influenza positive tests and influenza admissions to hospital for the Ontario, 2007/08 season. b) Corresponding cumulative distribution functions (CDF).

<p>Considering that 42% of viral isolates were influenza B, the two time series are in close agreement with a correlation coefficient (<i>r</i>) of 0.95 (95% CI: 0.92, 0.97). As a result of multiple circulating strains, the alert was triggered 15 weeks before peak influenza admissions and remained on for 25 weeks. Influenza A (A/Solomon Islands/03/2006(H1N1)) was responsible for the initial increase in hospitalizations in January with A/Brisbane/10/2007 (H3N2) and B strain (B/Florida/4/2006 (belonging to the B/Yamagata lineage)) circulating in late spring.