FluWatch report: December 11 to December 17, 2016 (week 50)

Download the alternative format
(PDF format, 826 KB, 9 pages)

Organization: Public Health Agency of Canada

Date published: 2016-12-23

  • Seasonal influenza activity continues to increase in Canada, with greater numbers of influenza detections, hospitalizations and outbreaks being reported in week 50.
  • A total of 692 positive influenza detections were reported in week 50. Influenza A(H3N2) continues to be the most common subtype detected.
  • Eighteen laboratory-confirmed influenza outbreaks were reported in week 50, with the majority occurring in long-term care facilities.
  • Adults aged 65+ years accounted for the largest proportion of hospitalizations and deaths reported from adult sentinel networks and participating Provinces and Territories.
  • The current FluWatch report is the last report for the 2016 calendar year. The next FluWatch report will be published on Friday, January 6 2017 and will contain data for weeks 51 and 52.
  • For more information on the flu, see our Flu (influenza) web page.

In week 50, a total of 19 regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 20 regions across 11 provinces and territories (BC, AB, SK, ON, NS, NB, PE, NF, NT, YT and NU). Localized activity was reported in eight regions across four provinces (BC, AB, ON and NS). 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 50
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 50, a total of 19 regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 22 regions across all provinces and territories (excluding NB). Localized activity was reported in 11 regions across five provinces (BC, AB, SK, ON and NS). Widespread activity was reported in one region of Alberta.

The percentage of tests positive for influenza continues to increase with 11.7% of tests positive for influenza in week 50. Compared to the previous influenza A(H3N2)-predominant season in 2014-15, the percent positive (11.7%) was lower than the percent positive reported in week 50 of the 2014-15 season (25.9%). 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 50
Figure 2

The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the start and end of seasonal influenza activity.

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 52 140 <5 7
47 54 200 0 9
48 91 272 <5 7
49 148 414 <5 12
50 354 396 <5 17
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 50, there were 692 positive influenza tests. To date, a total of 2,809 laboratory confirmed influenza detections have been reported. Influenza A(H3N2) is the most common subtype detected, representing 72% of detections. 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 50
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 (December 11, 2016 to December 17, 2016) Cumulative (August 28, 2016 to December 17, 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 82 0 37 45 1 404 2 356 46 16 420
AB 246 0 173 73 3 988 5 897 86 21 1009
SK 0 0 0 0 0 83 0 18 65 4 87
MB 1 0 1 0 0 14 0 14 0 1 15
ON 161 1 136 24 3 575 11 463 101 22 597
QC 146 0 7 139 10 433 0 53 379 33 466
NB 2 0 1 1 0 12 1 6 5 3 15
NS 6 0 0 6 0 21 0 1 20 0 21
PE 2 0 2 0 0 6 0 6 0 0 6
NL 3 0 0 3 0 20 0 16 4 3 23
YT 22 0 14 8 0 139 0 115 24 1 140
NT 1 0 1 0 0 3 0 3 0 0 3
NU 3 0 3 0 0 6 0 6 0 1 7
Canada 675 1 375 299 17 2704 19 1954 730 105 2809
PercentageTable Figure 3 - Footnote 2 98% 0% 56% 44% 2% 96% 1% 72% 27% 4% 100%

To date this season, detailed information on age and type/subtype has been received for 2,389 laboratory confirmed influenza cases. Adults aged 65+ were the age group that accounted for the largest proportion of reported influenza cases (>37%) and the largest proportion of influenza A (H3N2) cases. Compared to the cases reported in the 2014-15 season at week 50, adults aged 65+ account for a smaller proportion of cases this season (approximately 37% in 2016-17 compared to 56% in 2014-15).

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 (December 11, 2016 to December 17, 2016) Cumulative (August 28, 2016 to December 17, 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 32 0 13 19 <5 >163 <5 107 56 22 >185 x%
5-19 79 0 31 48 6 >373 <5 266 107 19 >392 x%
20-44 101 0 47 54 <5 >445 <5 330 115 17 >462 x%
45-64 70 0 30 40 0 429 6 307 116 9 442 18%
65+ 182 0 69 113 <5 >894 <5 629 265 13 >907 x%
Total 464 0 190 274 13 2309 11 1639 659 80 2389 100%
PercentageTable 1 - Footnote 2 97% 0% 41% 59% 3% 97% 0% 71% 29% 3%

Healthcare Professionals Sentinel Syndromic Surveillance

In week 50, 1.3% of visits to healthcare professionals were due to ILI. The proportion of ILI visits slightly increased 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 50: 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 0.96%
36 0.96%
37 0.98%
38 0.96%
39 0.94%
40 1.03%
41 2.41%
42 1.04%
43 1.01%
44 1.39%
45 1.32%
46 0.97%
47 1.11%
48 1.07%
49 1.09%
50 1.34%

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 50, 18 laboratory confirmed influenza outbreaks were reported: 11 in long-term care (LTC) facilities, four in hospitals and three in institutional or community settings. Additionally, one ILI outbreak was reported in a school. Of the outbreaks with known strains or subtypes: 11 outbreaks were due to influenza A of which four were due to influenza A(H3N2) (two in LTC facilities and two in institutional or community settings) and seven were due to influenza A(UnS) (four in LTC facilities, two in hospitals and one in an institutional or community setting ).

To date this season, 88 outbreaks have been reported and the majority (70%) have occurred in LTC facilities. In comparison at week 50 in the 2014-15 season, the previous influenza A(H3N2)-predominant season, 183 outbreaks were reported, of which 77% occurred in LTC facilities.

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote 1 by report week, Canada, 2016-17, Week 50
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 1 13 3
50 4 11 3
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 50, 98 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote *. Influenza A accounted for all of the reported hospitalizations, of which 54 (56%) were influenza A(H3N2). Adults aged 65+ accounted for the largest proportion of hospitalizations (69%).

To date this season, 454 hospitalizations have been reported, of which 98% were due to influenza A. Among cases for which the subtype of influenza A was reported, almost all (319/320) were influenza A(H3N2). Adults 65+ accounted for approximately 64% of the hospitalizations. Fifteen ICU admissions and greater than seven deaths have been reported. The majority of deaths were reported in adults aged 65+ years.

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 50
Age Groups (years) Cumulative (August 28, 2016 to December 17, 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
x Supressed to prevent residual disclosure
0-4 32 <5 >32 (x%) 0  0% 0  0%
5-19 28 <5 >28 (x%) <5 x% <5 x%
20-44 33 <5 >33 (x%) <5 x% 0  0%
45-64 66 <5 >66 (x%) 5  33% 0  0%
65+ 285 <5 >285 (x%) 7  47% 7  88%
Total 444 10 454 (100%) 15  100% >7 100%

Pediatric Influenza Hospitalizations and Deaths

To date this season, 67 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. Children aged 0-2 years and 2-4 years, each accounted for approximately 30% of hospitalizations. Influenza A accounted for 85% (n=56) of the reported hospitalizations, of which 46% (n=31) were influenza A(H3N2) and the remainder were A(UnS). Additionally, six intensive care unit (ICU) admissions have been reported. No deaths have been reported this season.

Compared to the 2014-15, the previous influenza A(H3N2)-predominant season, where 139 cases were reported as of week 50, there have been approximately half the number of cases reported to date in the current season.

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 50
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 10
6-23 mo 9
2-4 yr 22
5-9 yr 13
10-16 yr 12
Figure 7 - Number of pediatric (≤16 years of age) hospitalizations reported by IMPACT sentinel hospital network, by week, Canada, 2016-17, Week 50
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 8 5 1 13
47 1 5 0 9
48 7 10 1 22
49 10 15 2 28
50 18 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

In week 50, 13 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN). All cases were due to influenza A and the majority (77%) were in adults aged 65+.

To date this season, greater than 55 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by CIRN. All hospitalized cases were due to influenza A. Adults aged 65+ accounted for approximately 74% of hospitalizations. To date, less than five ICU admissions and deaths have been reported.

Figure 8 - Cumulative numbers of adult hospitalizations (≥20 years of age) with influenza by type and age-group reported by the CIRN network, Canada, 2016-17, Week 50
Figure 8
Figure 8 - Text Description
Figure 8 - Cumulative numbers of adult hospitalizations (≥20 years of age) with influenza by type and age-group reported by the CIRN network, Canada, 2016-17
Age Group Total
20-44 yr <5
45-64 yr 13
65+ yr 42
Figure 9 - Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group (≥16 year of age), Canada 2015-16, Week 50
Figure 9

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

Figure 9 - Text Description
Figure 9 - Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group (≥20 year of age), CIRN, Canada, 2016-17
Age-group (years) Hospitalizations (n= >40) ICU admissions (n= <5) Deaths (n= <5)
- Supressed due to small values
20-44 4.0% 25.0% 0.0%
45-64 22.8% 0.0% 0.0%
65+ 73.7% 75.0% 100.0%

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 158 influenza viruses [136 A(H3N2), 7 A(H1N1), 15 influenza B]. All but one influenza A virus (n=135) and all 8 influenza B viruses characterized were antigentically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Seven influenza B viruses were similar to the strain which is included only in the quadirvalent vaccine.

In epidemiological week 50 the National Microbiology Laboratory detected a human case of influenza A(H3N2) variant virus (H3N2v), the virus was detected as part of routine virological surveillance for influenza. Genetic analysis of the virus revealed that it is closely related to the influenza A(H3N2) swine viruses currently circulating in swine in North America. Antigenic characterization of this virus showed that it is antigenically closely related to the candidate H3N2v vaccine virus A/Indiana/10/2011. Testing of the H3N2v virus for resistance to neuraminidase inhibitors (oseltamivir and zanamivir) using a functional assay and sequence analysis showed that the specimen was sensitive to oseltamivir and zanamivir. M gene sequencing of the virus revealed that it had a mutation known to confer resistance to amantadine.

Table 3 - Influenza strain characterizations, Canada, 2016-17, Week 50
Strain Characterization ResultsTable 3 - Footnote 1 Count Description
Influenza A (H3N2)
Antigenically
A/Hong Kong/4801/2014-like
51 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
84

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.

Antigenically
A/Indiana/10/2011-like
1

Viruses antigenically similar to A/Indiana/10/2011, a candidate H3N2v vaccine virusTable 3 - Footnote 3.

Influenza A (H1N1)
A/California/7/2009-like 7 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)
7 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 170 influenza viruses for resistance to oseltamivir and zanamivir and 57 influenza viruses for resistance to amantadine. All viruses were sensitive to oseltamivir and zanamivir. All 57 influenza A viruses were resistant to amantadine (Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, 2016-17, Week 50
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
A (H3N2) 148 0 (0%) 148 0 (0%) 50 50 (100%)
A (H3N2v) 1 0 (0%) 1 0 (0%) 1 1 (100%)
A (H1N1) 6 0 (0%) 6 0 (0%) 6 6 (100%)
B 15 0 (0%) 15 0 (0%) N/ATable 4 - Footnote * N/ATable 4 - Footnote *
TOTAL 170 0 (0%) 170 0 (0%) 57 57 (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.

Report a problem or mistake on this page
Please select all that apply:

Thank you for your help!

You will not receive a reply. For enquiries, contact us.

Date modified: