FluWatch report: November 13 to November 19, 2016 (week 46)

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Organization: Public Health Agency of Canada

Date published: 2016-11-25

  • Influenza activity is approaching seasonal levels with many regions in Canada reporting increasing influenza activity.
  • A total of 188 positive influenza detections were reported in week 46. Influenza A(H3N2) continues to be the most common subtype detected.
  • In week 46, 1.0% of visits to sentinel healthcare professionals were due to influenza-like symptoms.
  • Eight laboratory-confirmed influenza outbreaks were reported in week 46, an increase from the previous week with the majority in long-term care facilities.
  • Twenty-six hospitalizations were reported from participating provinces and territories in week 46; the majority due to influenza A.
  • For more information on the flu, see our Flu(influenza) web page.

IIn week 46, a total of 26 regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 20 regions across nine provinces and territories (BC, AB, SK, ON, QC, NB, PE, NF and NU). Localized activity was reported in seven regions across four provinces and territories (BC, AB, ON and YK). For more details on a specific region, click on the map.

Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, Week 46
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 in the mapping feature found in the Weekly Influenza Reports.
Figure 1 - Text Description

In week 46, a total of 26 regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 20 regions across nine provinces and territories (BC, AB, SK, ON, QC, NB, PE, NF and NU). Localized activity was reported in seven regions across four provinces and territories (BC, AB, ON and YK).

In week 46, the percentage of tests positive for influenza remained similar to the previous week with 4.5% of tests positive for influenza. The percentage of tests positive for influenza is approaching seasonal levels. For data on other respiratory virus detections, see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada (PHAC) website.

Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2016-17
Figure 2
Figure 2 - Text Description
Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2016-17
Report Week A(Unsubtyped) A(H3) A(H1)pdm09 Influenza B
35 0 <5 0 0
36 <5 0 <5 9
37 <5 17 0 <5
38 11 28 <5 <5
39 14 41 <5 7
40 0 47 <5 <5
41 10 31 0 <5
42 14 49 <5 6
43 16 76 <5 <5
44 19 110 <5 9
45 31 150 <5 11
46 75 125 <5 7
47 0 0 0 0
48 0 0 0 0
49 0 0 0 0
50 0 0 0 0
51 0 0 0 0
52 0 0 0 0
1 0 0 0 0
2 0 0 0 0
3 0 0 0 0
4 0 0 0 0
5 0 0 0 0
6 0 0 0 0
7 0 0 0 0
8 0 0 0 0
9 0 0 0 0
10 0 0 0 0
11 0 0 0 0
12 0 0 0 0
13 0 0 0 0
14 0 0 0 0
15 0 0 0 0
16 0 0 0 0
17 0 0 0 0
18 0 0 0 0
19 0 0 0 0
20 0 0 0 0
21 0 0 0 0
22 0 0 0 0
23 0 0 0 0
24 0 0 0 0
25 0 0 0 0
26 0 0 0 0
27 0 0 0 0
28 0 0 0 0
29 0 0 0 0
30 0 0 0 0
31 0 0 0 0
32 0 0 0 0
33 0 0 0 0
34 0 0 0 0

Nationally in week 46, there were 188 positive influenza tests. BC, AB and ON accounted for the majority (85%) of influenza detections in week 46. To date, influenza A(H3N2) is the most common subtype detected, representing 73% of laboratory-confirmed cases. For more detailed weekly and cumulative influenza data, see the text descriptions for Figures 2 and 3 or the Respiratory Virus Detections in Canada Report.

Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, 2016-17
Figure 3
Figure 3 - Text Description
Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, 2016-17
Reporting
provincesTable Figure 3 - Footnote 1
Weekly (October 30, 2016 to November 5, 2016) Cumulative (August 28, 2016 to November 5, 2016)
Influenza A B Influenza A B A & B
Total
A
Total
A
(H1)pdm09
A
(H3)
ATable Figure 3 - Footnote UnS B
Total
A
Total
A
(H1)pdm09
A
(H3)
ATable Figure 3 - Footnote UnS B
Total
BC 46 0 46 0 2 244 2 234 8 12 256
AB 63 0 62 1 3 264 3 242 19 13 277
SK 2 0 0 2 0 19 0 2 17 4 23
MB 1 0 1 0 0 9 0 9 0 1 10
ON 43 2 34 7 2 169 8 125 36 17 186
QC 18 0 3 15 2 92 0 7 85 10 102
NB 1 0 0 1 0 5 0 2 2 1 6
NS 1 0 0 1 0 5 0 1 3 0 5
PE 0 0 0 0 0 3 0 3 0 0 3
NL 0 0 0 0 0 5 0 4 1 1 6
YT 4 0 4 0 0 52 0 50 2 0 52
NT 0 0 0 0 0 0 0 0 0 0 0
NU 0 0 0 0 0 0 0 0 0 1 1
Canada 179 2 150 27 9 867 13 679 175 60 927
PercentageTable Figure 3 - Footnote 2 95% 1% 84% 15% 5% 94% 1% 78% 20% 6% 100%

To date this season, detailed information on age and type/subtype has been received for 826 laboratory confirmed influenza cases. Adults aged 65+ accounted for over 40% of reported influenza cases. Among cases of influenza A(H3N2), adults aged 65+ accounted for 44% of cases.

Table 1 - Weekly and cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reporting Table 1 - Footnote 1, Canada, 2016-17
Age groups (years) Weekly (November 13, 2016 to November 19, 2016) Cumulative (August 28, 2016 to November 19, 2016)
Influenza A B Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) ATable 1 - Footnote UnS Total A Total A(H1) pdm09 A(H3) ATable 1 - Footnote UnS Total #
0-4 5 0 <5 <5 0 51 0 40 11 12 63
5-19 16 0 9 7 0 88 0 75 13 5 93
20-44 15 0 9 6 0 >143 <5 114 25 11 >143
45-64 >24 <5 15 8 0 153 5 120 28 7 160
65+ 59 0 27 32 0 >348 <5 272 74 8 >348
Total >119 <5 >63 >53 0 783 11 621 151 43 826
PercentageTable 1 - Footnote 2 100% 1% 53% 46% 0% 95% 1% 79% 19% 5%  

Healthcare Professionals Sentinel Syndromic Surveillance

IIn week 46, 1.0% of visits to healthcare professionals were due to ILI, a decrease from the previous week.

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17

Number of Sentinels Reporting Week 46: 108

Figure 4
Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.
Figure 4 - Text Description
Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17
Report week % Visits for ILI
35 0.94%
36 0.94%
37 0.96%
38 0.93%
39 0.92%
40 1.04%
41 2.39%
42 1.04%
43 0.99%
44 1.34%
45 1.52%
46 1.03%
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Are you a primary healthcare practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel?
Please visit our Influenza Sentinel page for more details.

In week 46, eight laboratory confirmed influenza outbreaks were reported. Six outbreaks were reported  in long-term care (LTC) facilities and two outbreaks were reported in a hospital. Of the outbreaks with known strains or subtypes, one outbreak (in a LTC facility) was due to influenza A(H3N2) and three outbreaks (two in LTC facilities and one in a hospital) were due to influenza A(unsubtyped). An additional outbreak due to ILI was reported in a school. To date this season, 41 outbreaks have been reported and the majority (66%) have occurred in LTC facilities.

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote 1 by report week, Canada, 2016-17
Figure 5
Figure 5 - Text Description
Figure 5 - Overall number of new laboratory-confirmed influenza outbreaks by report week, Canada, 2016-17
Report week Hospitals Long Term Care Facilities Other
35 0 0 0
36 0 0 0
37 0 2 0
38 1 1 0
39 1 3 0
40 0 0 0
41 0 3 0
42 0 3 0
43 0 3 0
44 2 5 0
45 1 1 0
46 2 6 0
47 0 0 0
48 0 0 0
49 0 0 0
50 0 0 0
51 0 0 0
52 0 0 0
1 0 0 0
2 0 0 0
3 0 0 0
4 0 0 0
5 0 0 0
6 0 0 0
7 0 0 0
8 0 0 0
9 0 0 0
10 0 0 0
11 0 0 0
12 0 0 0
13 0 0 0
14 0 0 0
15 0 0 0
16 0 0 0
17 0 0 0
18 0 0 0
19 0 0 0
20 0 0 0
21 0 0 0
22 0 0 0
23 0 0 0
24 0 0 0
25 0 0 0
26 0 0 0
27 0 0 0
28 0 0 0
29 0 0 0
30 0 0 0
31 0 0 0
32 0 0 0
33 0 0 0
34 0 0 0

In week 46, 26 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote *.  Influenza A accounted for 88% (n=23) of the reported hospitalizations, of which 83% (n=19) were influenza A(H3N2). Adults aged 65+ accounted for the largest proportion of hospitalizations (54%).

To date this season, 136 hospitalizations have been reported, of which 112 (81%) were due to influenza A(H3N2). Adults 65+ accounted for more than 50% of the hospitalizations. Six ICU admissions (all due to influenza A) and less than five deaths have been reported.

Table 2 - Cumulative number of hospitalizations, ICU admissions and deaths by age and influenza type reported by participating provinces and territories, Canada 2016-17
Age Groups (years) Cumulative (August 28, 2016 to November 19, 2016)
Hospitalizations ICU Admissions Deaths
Influenza A Total Influenza B Total Total [# (%)] Influenza A and B Total % Influenza A and B Total %
Note: Influenza-associated hospitalizations are not reported to PHAC by: BC, NU, and QC. Only hospitalizations that require intensive medical care are reported by SK. ICU admissions
– Supressed to prevent residual disclosure
0-4 7 <5 >7(–%) 0 –% 0 0%
5-19 10 <5 >10(–%) >5 –% 0 0%
20-44 12 <5 >12(–%) 0 –% 0 0%
45-64 19 <5 >19(–%) >5 –% 0 0%
65+ 81 <5 >81(–%) >5 –% >5 100%
Total 129 7 136(100%) 6 100% >5 100%

Pediatric Influenza Hospitalizations and Deaths

To date this season, 29 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. Children from all age groups are being affected similarly. Influenza A accounted for 79% (n=23) of the reported hospitalizations, of which 70% (n=16) were influenza A(H3N2).

Figure 6 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, 2016-17
Figure 5
Figure 6 - Text Description
Figure 6 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, 2016-17
Age Group Total
0-5 mo 5
6-23 mo 5
2-4 yr 8
5-9 yr 5
10-16 yr 6
Figure 7 - Number of pediatric (≤16 years of age) hospitalizations reported by IMPACT sentinel hospital network, by week, Canada, 2016-17
Figure 5

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2015-16

Figure 7 - Text Description
Figure 7 - Number of pediatric (≤16 years of age) hospitalizations reported by IMPACT sentinel hospital network, by week, Canada, 2016-17
Report week 2016-17 Average Min Max
35 0 0 0 0
36 1 0 0 0
37 0 1 0 2
38 0 1 0 2
39 3 0 0 1
40 2 0 0 1
41 0 1 0 2
42 4 1 0 1
43 4 1 0 3
44 5 2 1 4
45 3 3 2 4
46 7 5 1 13
47 #N/A 5 0 9
48 #N/A 10 1 22
49 #N/A 15 2 28
50 #N/A 24 4 47
51 #N/A 35 4 71
52 #N/A 47 7 92
1 #N/A 37 3 75
2 #N/A 36 6 60
3 #N/A 37 2 67
4 #N/A 34 5 47
5 #N/A 39 10 57
6 #N/A 38 15 79
7 #N/A 41 15 118
8 #N/A 48 25 134
9 #N/A 59 12 172
10 #N/A 48 17 114
11 #N/A 45 17 118
12 #N/A 39 14 96
13 #N/A 33 14 57
14 #N/A 27 12 56
15 #N/A 25 14 56
16 #N/A 22 10 41
17 #N/A 18 9 37
18 #N/A 15 6 28
19 #N/A 10 5 18
20 #N/A 9 4 18
21 #N/A 6 2 10
22 #N/A 4 1 7
23 #N/A 2 0 4
24 #N/A 2 0 5
25 #N/A 1 0 3
26 #N/A 1 0 2
27 #N/A 0 0 2
28 #N/A 1 0 1
29 #N/A 0 0 2
30 #N/A 0 0 0
31 #N/A 0 0 0
32 #N/A 0 0 1
33 #N/A 0 0 0
34 #N/A 1 0 2

Adult Influenza Hospitalizations and Deaths

To date this season, less than five laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN).

Note: The number of hospitalizations reported through CIRN and IMPACT represents a subset of all influenza-associated pediactric  and adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 91 influenza viruses [77 A(H3N2), 5 A(H1N1), 9 influenza B].

Table 3 - Influenza strain characterizations, Canada, 2016-17
Strain Characterization ResultsTable 3 - Footnote 1 Count Description
Influenza A (H3N2)
Antigenically
A/Hong Kong/4801/2014-like
32 Viruses antigenically similar to A/Hong Kong/4801/2014, the A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
GeneticallyTable 3 - Footnote 2
A/Hong Kong/4801/2014-like
45 Viruses belonging to genetic group 3C.2a. A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
Influenza A (H1N1)
A/California/7/2009-like 5 Viruses antigenically similar to A/California/7/2009, the A(H1N1) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine influenza vaccine.
Influenza B
B/Brisbane/60/2008-like
(Victoria lineage)
7 Viruses antigenically similar to B/Brisbane/60/2008, the influenza B component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent influenza vaccine
B/Phuket/3073/2013-like
(Yamagata lineage)
2 Viruses antigenically similar to B/Phuket/3073/2013, the additional influenza B component of the 2016-17 Northern Hemisphere quadrivalent influenza vaccine.

During the 2016-17 season, the National Microbiology Laboratory (NML) has tested 81 influenza viruses for resistance to oseltamivir and zanamivir and 39 influenza viruses for resistance to amantadine. All viruses weres sensitive to oseltamivir and zanamivir. All 39 influenza A viruses were resistant to amantadine (Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, 2016-17
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
A (H3N2) 67 0 (0%) 67 0 (0%) 36 36 (100%)
A (H1N1) 5 0 (0%) 5 0 (0%) 3 3 (100%)
B 9 0 (0%) 9 0 (0%) N/ATable 4 - Footnote * N/ATable 4 - Footnote *
TOTAL 81 0 (0%) 81 0 (0%) 39 39 (100%)

Abbreviations: Newfoundland/Labrador (NL), Prince Edward Island (PE), New Brunswick (NB), Nova Scotia (NS), Quebec (QC), Ontario (ON), Manitoba (MB), Saskatchewan (SK), Alberta (AB), British Columbia (BC), Yukon (YT), Northwest Territories (NT), Nunavut (NU).

Influenza-like-illness (ILI): Acute onset of respiratory illness with fever and cough and with one or more of the following - sore throat, arthralgia, myalgia, or prostration which is likely due to influenza. In children under 5, gastrointestinal symptoms may also be present. In patients under 5 or 65 and older, fever may not be prominent.

ILI/Influenza outbreaks

Schools:
Greater than 10% absenteeism (or absenteeism that is higher (e.g. >5-10%) than expected level as determined by school or public health authority) which is likely due to ILI.
Note: it is recommended that ILI school outbreaks be laboratory confirmed at the beginning of influenza season as it may be the first indication of community transmission in an area.
Hospitals and residential institutions:
two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case. Institutional outbreaks should be reported within 24 hours of identification. Residential institutions include but not limited to long-term care facilities (LTCF) and prisons.
Workplace:
Greater than 10% absenteeism on any day which is most likely due to ILI.
Other settings:
two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case; i.e. closed communities.

Note that reporting of outbreaks of influenza/ILI from different types of facilities differs between jurisdictions.

Influenza/ILI activity level

1 = No activity: no laboratory-confirmed influenza detections in the reporting week, however, sporadically occurring ILI may be reported

2 = Sporadic: sporadically occurring ILI and lab confirmed influenza detection(s) with no outbreaks detected within the influenza surveillance region Footnote

3 = Localized:

  1. evidence of increased ILIFootnote * and
  2. lab confirmed influenza detection(s) together with
  3. outbreaks in schools, hospitals, residential institutions and/or other types of facilities occurring in less than 50% of the influenza surveillance regionFootnote

4 = Widespread:

  1. evidence of increased ILIFootnote * and
  2. lab confirmed influenza detection(s) together with
  3. outbreaks in schools, hospitals, residential institutions and/or other types of facilities occurring in greater than or equal to 50% of the influenza surveillance regionFootnote

Note: ILI data may be reported through sentinel physicians, emergency room visits or health line telephone calls.

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