FluWatch report: September 21 to October 4, 2014 (Weeks 39 and 40)

Overall summary

  • Several influenza indicators (activity levels, influenza detections, ILI and hospitalizations) continued to increase in weeks 39 and 40. Influenza activity was reported in several regions in six provinces (BC, AB, SK, MB, ON & QC) over the two-week period.
  • Early season influenza detections show influenza A(H3N2) to be the predominant virus circulating, followed by co-circulation of influenza B.
  • In week 39, six influenza outbreaks and two ILI outbreaks were reported. No new outbreaks were reported in week 40.
  • Among laboratory detections and hospitalizations, the majority of cases were ≥65 years of age.

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Organization: Public Health Agency of Canada

Date published: 2014-10-10

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Influenza/ILI Activity (geographic spread)

In weeks 39 and 40, the number of regions in Canada reporting influenza/ILI activity increased compared to the previous two week period. In week 39, five regions (BC(2), AB(1), ON(2)) reported localized activity, and 11 regions (BC(1), AB(4), SK(1), MB(1), ON(2) and QC(2)) reported sporadic activity. In week 40, two regions in Ontario reported localized activity, and 11 regions (BC(3), AB(4), ON(2) and QC(2)) reported sporadic activity (Figure 1).

Figure 1. Map of overall influenza/ILI activity level by province and territory, Canada, Week 40

Figure 1
Figure 1 Legend

Note: Influenza/ILI activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates and reported outbreaks. Please refer to detailed definitions at the end of the report. Maps from previous weeks, including any retrospective updates, are available on the Flu Activity website.

   Figure 1 Map of overall influenza/ILI activity level by province and territory, Canada, Week 30 - Text Description

In week 40, two regions in Ontario reported localized activity, and 11 regions (BC(3), AB(4), ON(2) and QC(2)) reported sporadic activity. No data was reported for one region (PE).

Influenza and Other Respiratory Virus Detections

The number of positive influenza tests increased during weeks 39 and 40. The percent positive for influenza detections remains low, and reached 1.2% in week 40 (Figure 2). To date, 84% of influenza detections have been influenza A, and the majority of those subtyped have been A(H3) (Table 1). Among cases with reported age, the largest proportion was in those ≥65 years of age (55%) (Table 2).

Figure 2. Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2014-15

Figure 2
   Figure 2 Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2014-15 - Text Description

The number of positive influenza tests increased during weeks 39 and 40. The percent positive for influenza detections remains low, and reached 1.2% in week 40.

In weeks 39 and 40, detections of other respiratory viruses were at inter-seasonal levels (RSV, coronavirus, and human metapneumovirus). Detections of parainfluenza were in keeping with their usual pattern of seasonal circulation. Detections of adenovirus were higher than in previous seasons. Detections of rhinovirus increased in week 39 to a level higher than observed in previous seasons, but decreased in week 40 (figure 3).

For more details, see the weekly Respiratory Virus Detections in Canada Report.

Figure 3. Number of positive laboratory tests for other respiratory viruses by report week, Canada, 2014-15

Figure 3
RSV: Respiratory syncytial virus; hMPV: Human metapneumovirus
   Figure 3 Number of positive laboratory tests for other respiratory viruses by report week, Canada, 2014-15 - Text Description

In weeks 39 and 40, detections of other respiratory viruses were at inter-seasonal levels (RSV, coronavirus, and human metapneumovirus). Detections of parainfluenza were in keeping with their usual pattern of seasonal circulation. Detections of adenovirus were higher than in previous seasons. Detections of rhinovirus increased in week 39 to a level higher than observed in previous seasons, but decreased in week 40.

Table 1: Weekly and cumulative numbers of positive influenza specimens by type, subtype and province, Canada, 2014-15
Reporting provincesFootnote 1 Two weeks (September 21 to October 4, 2014) Cumulative (August 24 to October 4, 2014)
Influenza A B Influenza A B
A Total A(H1)pdm09 A(H3) A Footnote (Uns) B Total A Total A(H1)pdm09 A(H3) A(UnS) B Total
BC 18 0 0 18 1 25 2 5 18 2
AB 18 0 16 2 2 29 0 27 2 4
SK 1 0 0 1 0 2 0 0 2 0
MB 1 0 1 0 0 1 0 1 0 0
ON 8 1 6 1 2 13 1 9 3 4
QC 5 0 0 5 0 12 0 0 12 6
NB 0 0 0 0 0 0 0 0 0 0
NS 0 0 0 0 0 0 0 0 0 0
PE 0 0 0 0 1 0 0 0 1 0
NL 1 0 0 1 0 1 0 0 1 0
Canada 52 1 23 28 5 84 3 42 39 16
Percentage Footnote 2 91.2% 1.9% 44.2% 53.8% 8.8% 84.0% 3.6% 50.0% 46.4% 16.0%
Table 2. Weekly and cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reportingFootnote 1,Footnote 3, Canada, 2014-15
Age groups (years) Two weeks
(September 21 to October 4, 2014)
Cumulative
(August 24 to October 4, 2014)
Influenza A B Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) A Footnote (Uns) Total A Total A(H1) pdm09 A(H3) A (UnS) Total # %
<5 4 0 2 2 1 31 3 11 17 11 42 16.0%
5-19 5 0 3 2 0 26 0 16 10 3 29 11.0%
20-44 3 0 1 2 0 22 0 5 17 2 24 9.1%
45-64 3 0 0 3 2 29 0 6 23 17 46 17.5%
65+ 6 0 1 5 0 108 1 44 63 14 122 46.4%
Unknown 0 0 0 0 0 0 0 0 0 0 0 0.0%
Total 21 0 7 14 3 216 4 82 130 47 263 100.0%
PercentageFootnote 2 87.5% 0.0% 33.3% 66.7% 12.5% 82.1% 1.9% 38.0% 60.2% 17.9%    

Influenza Strain Characterizations

The National Microbiology Laboratory (NML) has not yet reported any influenza strain characterizations for the 2014-15 season (Figure 4).

Figure 4. Influenza strain characterizations, Canada, 2014-2015, N = 0

The National Microbiology Laboratory (NML) has not yet conducted antigenic characterization of influenza viruses collected during the 2014-15 season.

The NML receives a proportion of the number of influenza positive specimens from provincial laboratories for strain characterization and antiviral resistance testing. Characterization data reflect the results of haemagglutination inhibition (HAI) testing compared to the reference influenza strains recommended by WHO.

The recommended components for the 2014-2015 northern hemisphere trivalent influenza vaccine include: an A/California/7/2009(H1N1)pdm09-like virus, an A/Texas/50/2012 (H3N2)-like virus, and a B/Massachusetts/2/2012-like virus (Yamagata lineage). For quadrivalent vaccines, the addition of a B/Brisbane/60/2008-like virus is recommended.