FluWatch report: November 27 to December 3, 2016 (week 48)

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Organization: Public Health Agency of Canada

Date published: 2016-12-09

  • Influenza activity has reached seasonal levels with many regions in Canada reporting increasing influenza activity.
  • A total of 201 positive influenza detections were reported in week 48. Influenza A(H3N2) continues to be the most common subtype detected.
  • In week 48, 1.1% of visits to sentinel healthcare professionals were due to influenza-like symptoms.
  • Two laboratory-confirmed influenza outbreaks were reported in week 48 with all occurring in long-term care facilities.
  • Twenty-eight hospitalizations were reported from participating provinces and territories in week 48; the majority due to influenza A(H3N2).
  • For more information on the flu, see our Flu (influenza) web page.

In week 48, a total of 19 regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 24 regions across ten provinces and territories (AB, SK, ON, QC, NS, PE, NF,NT, YT and NU). Localized activity was reported in five regions across three provinces (AB, ON and SK). For more details on a specific region, click on the map. 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 48
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 48, a total of 19 regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 24 regions across ten provinces and territories (AB, SK, ON, QC, NS, PE, NF, NT, YT and NU). Localized activity was reported in five regions across three provinces (AB, ON and SK). For more details on a specific region, click on the map..

In week 48, the percentage of tests positive for influenza increased with 7.2% of tests positive for influenza. The percentage of tests positive for influenza is at seasonal levels with percent positivity remaining above 5% for two consecutive weeks. 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, Week 48
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 48, there were 201 positive influenza tests. BC, AB and ON accounted for the majority (79%) of influenza detections in week 48. To date, influenza A(H3N2) is the most common subtype detected, representing 71% 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, Week 48
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 27, 2016 to December 3, 2016) Cumulative (August 28, 2016 to December 3, 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 1373 laboratory confirmed influenza cases. Adults aged 65+ accounted for over 38% of reported influenza cases. Among cases of influenza A(H3N2), adults aged 65+ accounted for 40% 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 27, 2016 to December 3, 2016) Cumulative (August 28, 2016 to December 3, 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 23 0 12 11 0 95 0 67 28 16 111 8%
5-19 41 0 18 23 <5 188 0 139 49 6 194 14%
20-44 64 0 30 34 <5 >259 <5 195 64 15 >274 –%
45-64 58 0 21 37 0 264 6 187 71 9 273 20%
65+ 70 0 37 33 0 >506 <5 388 118 9 >515 –%
Total 256 0 118 138 5 1318 12 976 330 55 1373 100%
PercentageTable 1 - Footnote 2 98% 0% 46% 54% 2% 96% 1% 74% 25% 4%    

Healthcare Professionals Sentinel Syndromic Surveillance

In week 48, 1.1% of visits to healthcare professionals were due to ILI. The proportion of ILI visits remained constant since the previous week.

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

Number of Sentinels Reporting Week 48: 106

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 1.12%
48 1.10%

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 48, two laboratory confirmed influenza outbreaks were reported, both in long-term care (LTC) facilities. To date this season, 52 outbreaks have been reported and the majority (71%) have occurred in LTC facilities.

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote 1 by report week, Canada, 2016-17, Week 48
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 2 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 48, 28 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote *. Influenza A accounted for all of the reported hospitalizations, of which 82% (n=23) were influenza A(H3N2). Adults aged 65+ accounted for the largest proportion of hospitalizations (61%).

To date this season, 204 hospitalizations have been reported, of which 163 (80%) were due to influenza A(H3N2). Adults 65+ accounted for 62% of the hospitalizations. Eighteen ICU admissions (majority were asspocated  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, Week 48
Age Groups (years) Cumulative (August 28, 2016 to December 3, 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 10 <5 >10(–%) <5 –% 0 0%
5-19 17 <5 >17(–%) <5 –% 0 0%
20-44 16 <5 >16(–%) <5 –% 0 0%
45-64 30 <5 >30(–%) <5 –% 0 0%
65+ 123 <5 >123(–%) 8 44% <5 100%
Total 196 8 204(100%) 18 100% <5 100%

Pediatric Influenza Hospitalizations and Deaths

To date this season, 36 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 83% (n=30) of the reported hospitalizations, of which 70% (n=21) 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, Week 48
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 6
2-4 yr 10
5-9 yr 8
10-16 yr 7
Figure 7 - Number of pediatric (≤16 years of age) hospitalizations reported by IMPACT sentinel hospital network, by week, Canada, 2016-17, Week 48
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 6 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, fourteen 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 114 influenza viruses [97 A(H3N2), 6 A(H1N1), 11 influenza B]. All  influenza A viruses (n=103) and 8 influenza B viruses characterized were antigentically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Three influenza B viruses were similar to the strain which was included only in the quadirvalent vaccine.

Table 3 - Influenza strain characterizations, Canada, 2016-17, Week 48
Strain Characterization ResultsTable 3 - Footnote 1 Count Description
Influenza A (H3N2)
Antigenically
A/Hong Kong/4801/2014-like
45 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
52

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 45 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 13 isolates. The majority of viruses belonging to genetic group 3C.3a are inhibited by antisera raised against A/Hong Kong/4801/2014Table 3 - Footnote 3.

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)
8 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 124 influenza viruses for resistance to oseltamivir and zanamivir and 48 influenza viruses for resistance to amantadine. All viruses were sensitive to oseltamivir and zanamivir. All 48 influenza A viruses were resistant to amantadine (Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, 2016-17, Week 48
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
A (H3N2) 108 0 (0%) 108 0 (0%) 43 43 (100%)
A (H1N1) 5 0 (0%) 5 0 (0%) 5 5 (100%)
B 11 0 (0%) 11 0 (0%) N/ATable 4 - Footnote * N/ATable 4 - Footnote *
TOTAL 124 0 (0%) 124 0 (0%) 48 48 (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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