January 30 to February 5, 2011 (Week 05)

Map: Map of overall Influenza activity level by province and territory, Canada, Week 5

In week 05, 18 regions reported localized activity (in BC(2), AB(2), ON(6), QC(2), NS(1), NB(4) & PE(1)), 27 regions reported sporadic activity (in all provinces and territories except YK) and 11 regions presented no activity.

Graph: Number of influenza surveillance regions reporting widespread or localized activity, Canada, by report week, 2010-2011 (n=56)

In week 05, 18 regions reported localized activity. No regions reported widespread influenza activity.

Graph: Overall number of influenza outbreaks, Canada, by report week, 2010-2011

During week 05, 29 new ILI/influenza outbreaks were reported: 11 in long-term care facilities (LTCF) in ON(4), QC(4), NB (2) and PE(1); 9 school outbreaks in BC(1), NB(7) and NL(1); 2 outbreaks in hospitals in ON; and 7 outbreaks in other facilities in BC(1) and ON(6).

Graph: Influenza-like illness (ILI) consultation rates, Canada, by report week, 2010-2011 compared to 1996/97 through to 2008/09 seasons

During week 05, the national ILI consultation rate was 29.9 consultations per 1,000 patient visits, which is similar to week 04 with 26.6 consultations per 1,000. This rate is still within the expected levels for this time of year.

Table: Weekly & Cumulative numbers of positive influenza specimens by Provincial Laboratories, Canada, 2010-2011

Of the 1359 positive tests reported during week 05, 401 (30%) specimens were reported as influenza A/H3N2, 88 (7%) as pandemic H1N1 2009, 101 (7%) as influenza B and 769 (57%) as unsubtyped influenza A. The majority of influenza virus detections to date this season were influenza A viruses (96.8% or 10471/10821). Since the beginning of the season, 88.0% of the subtyped positive influenza A specimens were influenza A/H3N2.In week 05, detections of pandemic H1N1 2009 represented 18.0% of all subtyped influenza A specimens, an increase from 12.6% in week 04. Detections of influenza B increased slightly from 5.4% of all positive influenza specimens in week 04 to 7.4% in week 05.

Table: Weekly & Cumulative numbers of positive influenza specimens by age groups reported through case-based laboratory reporting, Canada, 2010-2011

During week 05, 51.8% (72/139) of cases with A/H3N2 reported through the detailed case-based laboratory reporting were aged 65 years or older, while since August 29, 2010, the proportion was 49.8% (1384/2778).

Graph: Influenza tests reported and percentage of tests positive, Canada, by report week, 2010-2011

The proportion of tests that were positive for influenza during week 05 was 19.8%. The proportion of positive tests decreased from a peak at week 52, but increased slightly in week 05, likely due to an increase in the proportion of positive tests in Ontario and the Atlantic provinces.

Graph: Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2010-2011

The proportion of tests that were positive for influenza during week 05 was 19.8%. The proportion of positive tests for respiratory syncytial virus detections (RSV) increased slightly from at 15.0% to 16.9% of specimens tested while low levels of parainfluenza (2.1%) and rhinovirus (4.0%) continue to be reported.

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Definitions for the 2010-2011 season