FluWatch report: November 20 to November 26, 2016 (week 47)

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Organization: Public Health Agency of Canada

Date published: 2016-12-02

  • Influenza activity is reaching seasonal levels with many regions in Canada reporting increasing influenza activity.
  • A total of 256 positive influenza detections were reported in week 47. Influenza A(H3N2) continues to be the most common subtype detected.
  • In week 47, 1.2% of visits to sentinel healthcare professionals were due to influenza-like symptoms.
  • Nine laboratory-confirmed influenza outbreaks were reported in week 47 with the majority in long-term care facilities.
  • Thirty-seven hospitalizations were reported from participating provinces and territories in week 47; the majority due to influenza A(H3N2).
  • For more information on the flu, see our Flu (influenza) web page.

In week 47, a total of 18 regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 23 regions across ten provinces and territories (BC, AB, SK, ON, QC, NB, NS, YK,NF and NU). Localized activity was reported in seven regions across three provinces and territories (AB, ON and QC). 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 47
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 47, a total of 18 regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 23 regions across ten provinces and territories (BC, AB, SK, ON, QC, NB, NS, YK,NF and NU). Localized activity was reported in seven regions across three provinces and territories (AB, ON and QC).

In week 47, the percentage of tests positive for influenza increased with 5.7% of tests positive for influenza. The percentage of tests positive for influenza is entering 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 52 139 <5 7
47 89 172 0 10
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 47, there were 256 positive influenza tests. AB reported the largest proportion of positive influenza detections (35%) in week 47. To date, influenza A(H3N2) is the most common subtype detected, representing 78% 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 (November 20, 2016 to November 26, 2016) Cumulative (August 28, 2016 to November 26, 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 40 0 32 8 2 277 2 266 9 14 291
AB 90 0 70 20 0 355 4 326 25 13 368
SK 0 0 0 0 0 19 0 2 17 4 23
MB 4 0 3 1 0 13 0 12 1 1 14
ON 40 2 37 3 1 209 8 162 39 18 227
QC 38 0 7 31 4 130 0 14 116 14 144
NB 1 0 0 1 2 6 0 2 4 3 9
NS 0 0 0 0 0 5 0 1 4 0 5
PE 0 0 0 0 0 3 0 3 0 0 3
NL 5 0 0 5 0 10 0 4 6 1 11
YT 27 0 18 9 1 77 0 68 9 1 78
NT 0 0 0 0 0 0 0 0 0 0 0
NU 1 0 1 0 0 1 0 1 0 1 2
Canada 246 0 168 78 10 1105 14 861 230 70 1175
PercentageTable Figure 3 - Footnote 2 96% 0% 68% 32% 4% 94% 1% 78% 21% 6% 100%

To date this season, detailed information on age and type/subtype has been received for 1047 laboratory confirmed influenza cases. Adults aged 65+ accounted for over 41% of reported influenza cases. Among cases of influenza A(H3N2), adults aged 65+ accounted for 42% 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 20, 2016 to November 26, 2016) Cumulative (August 28, 2016 to November 26, 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 # %
<5 14 0 5 9 <5 67 0 49 18 16 83 8%
5-19 33 0 15 18 0 131 0 104 27 5 136 13%
20-44 28 0 16 12 0 >180 <5 143 37 11 >191 –%
45-64 30 0 13 17 <5 197 6 150 41 9 206 20%
65+ 60 0 38 22 0 >416 <5 329 87 9 >425 –%
Total 165 0 87 78 5 997 12 775 210 50 1047 100%
PercentageTable 1 - Footnote 2 97% 0% 53% 47% 3% 95% 1% 78% 21% 5%    

Healthcare Professionals Sentinel Syndromic Surveillance

In week 47, 1.2% of visits to healthcare professionals were due to ILI, a slight increase 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 47: 116

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 1.02%
41 2.35%
42 1.01%
43 0.98%
44 1.36%
45 1.32%
46 0.97%
47 1.15%

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 47, nine laboratory confirmed influenza outbreaks were reported. Eight outbreaks were reported  in long-term care (LTC) facilities and one outbreak was reported in a hospital. Of the outbreaks with known strains or subtypes, two outbreaks (in a LTC facility and in a hospital) were due to influenza A(H3N2). To date this season, 50 outbreaks have been reported and the majority (70%) 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 1
39 1 3 1
40 0 0 0
41 0 3 0
42 0 3 1
43 0 3 0
44 2 5 2
45 1 1 0
46 2 6 0
47 1 8 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 47, 37 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote *. Influenza A accounted for 97% (n=36) of the reported hospitalizations, of which 76% (n=25) were influenza A(H3N2). Adults aged 65+ accounted for the largest proportion of hospitalizations (60%).

To date this season, 175 hospitalizations have been reported, of which 135 (77%) were due to influenza A(H3N2). Adults 65+ accounted for 61% of the hospitalizations. Twelve ICU admissions (majority were due to influenza A[H3N2]) 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 26, 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 8 <5 >8(–%) 0 0% 0 0%
5-19 13 <5 >13(–%) <5 –% 0 0%
20-44 15 <5 >15(–%) <5 –% 0 0%
45-64 27 <5 >27(–%) <5 –% 0 0%
65+ 104 <5 >104(–%) 6 50% <5 100%
Total 167 8 175(100%) 12 100% <5 100%

Pediatric Influenza Hospitalizations and Deaths

To date this season, 30 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 80% (n=24) of the reported hospitalizations, of which 71% (n=17) 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

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

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 6
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

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

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 1 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, seven laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN).

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 105 influenza viruses [89 A(H3N2), 6 A(H1N1), 10 influenza B]. All  influenza A viruses (n=95) and 7 influenza B viruses characterized were antigentically or geneticall similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Three influenza B viruses were similar to the strain which included only the quadirvalent vaccine.

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
40 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
49

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.

Additionally, genetic characterization of the 40 influenza A (H3N2) viruses that underwent HI testing, determined that  27 viruses belonged to genetic group 3C.2a and 5 viruses belonged to genetic group 3C.3a. Sequencing is pending for the remaining 8 isolates. The majority of viruses belonging to genetic group 3C.3a are inhibited by antisera raised against A/Hong Kong/4801/2014.

Influenza A (H1N1)
A/California/7/2009-like 6 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)
3 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 102 influenza viruses for resistance to oseltamivir and zanamivir and 43 influenza viruses for resistance to amantadine. All viruses were 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) 88 0 (0%) 88 0 (0%) 39 39 (100%)
A (H1N1) 5 0 (0%) 5 0 (0%) 4 4 (100%)
B 9 0 (0%) 9 0 (0%) N/ATable 4 - Footnote * N/ATable 4 - Footnote *
TOTAL 102 0 (0%) 102 0 (0%) 43 43 (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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