FluWatch report:  February 5, 2017 to February 11, 2017 (week 6)

Overall Summary

  • Influenza indicators such as laboratory detections, outbreaks and sentinel influenza-like illness surveillance have been stable or increasing in the past four weeks.
  • Widespread or localized influenza activity was reported in at least one region in all provinces.
  • The percentage of tests positive for influenza has remained relatively stable for the past four weeks (ranging from 23% to 24% of tests positive for influenza).
  • In week 06, 67 laboratory confirmed outbreaks were reported (up from 57 in the previous week); the majority in long-term care facilities and due to influenza A.
  • In week 06, the number of hospitalizations reported by participating provinces and territories and sentinel hospital networks decreased. 
  • A(H3N2) continues to be the most common type of influenza affecting Canadians.
  • The majority of laboratory detections, hospitalizations and deaths have been among adults aged 65+ years.
  • For more information on the flu, see our Flu(influenza) web page.

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Date published: 2017-02-17

Influenza/Influenza-like Illness Activity (geographic spread)

In week 06, six regions (one each in each territory and two regions in NB) are reported no influenza or influenza-like illness activity. Sporadic influenza activity was reported in 21 regions across ten provinces and territories. Localized activity was reported in 22 regions across seven provinces. Widespread activity was reported in three provinces (one region each in PE and MB and two in SK). 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 6

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 06, six regions (one each in each territory and two regions in NB) are reported no influenza or influenza-like illness activity. Sporadic influenza activity was reported in 21 regions across ten provinces and territories. Localized activity was reported in 22 regions across seven provinces.

Laboratory Confirmed Influenza Detections

In week 06, the percentage of tests positive for influenza remained similar to the previous week at 24%. Peak influenza detections occurred in week 02 at 27%. Since week 02, detections have remained relatively stable (ranging from 23% to 24% in weeks 03 to 06). 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 6

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
50 305 467 <5 18
51 535 750 <5 17
52 857 1064 <5 33
1 1444 1360 <5 38
2 1516 2118 10 39
3 1354 1412 0 47
4 1336 1220 <5 47
5 1222 1290 7 62
6 1316 1146 6 81

Nationally in week 06, 2,472 positive influenza detections were reported, down slightly from 2,547 reported the previous week. The Altantic provinces and QC were the only regions reporting increased influenza detections in week 06. To date, 22,921 laboratory confirmed influenza detections have been reported, of which 98% have been influenza A. Influenza A(H3N2) is the most common subtype detected, representing over 99% of subtyped influenza A detections (12386/12441). 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 6

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 (Febuary 5, 2017 to Febuary 11, 2017) Cumulative (August 28, 2016 to Febuary 11, 2017)
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 446 3 356 87 34 3425 9 1768 1648 132 3557
AB 169 0 89 80 7 3321 8 3161 152 67 3388
SK 74 0 53 21 3 1318 0 710 608 19 1337
MB 31 0 7 24 1 183 0 78 105 11 194
ON 562 2 486 74 20 7126 32 5782 1312 93 7219
QC 925 0 73 852 16 6036 0 434 5600 137 6173
NB 101 1 10 90 0 367 2 52 313 3 370
NS 32 0 0 32 0 188 0 13 175 1 189
PE 21 0 21 0 0 111 2 109 0 1 112
NL 21 0 0 21 0 87 0 43 44 5 92
YT 3 0 3 0 0 197 0 150 47 2 199
NT 3 0 0 3 0 35 0 32 3 0 35
NU 3 0 2 1 0 55 0 54 1 1 56
Canada 2391 6 1100 1285 81 22449 53 12386 10008 472 22921
PercentageTable Figure 3 - Footnote 2 97% 0% 46% 54% 3% 98% 0% 55% 45% 2% 100%

To date, detailed information on age and type/subtype has been received for 16,187 laboratory-confirmed influenza cases (Table 1). Among cases with reported age and type/subtype information, adults aged 65+ accounted for almost half of the reported influenza cases. Among cases of influenza A(H3N2), adults aged 65+ represented  47% of cases, followed by adults aged 20-64 (35% of cases). In the previous influenza A(H3N2)-predominant season in 2014-15, adults aged 65+ represented  66% of cases and adults aged 20-64 represented 27% of cases.

Table 1 - Weekly and cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reportingTable 1 - Footnote 1, Canada, 2016-17, week 6
Age groups (years) Weekly (February 5 to February 11, 2017) Cumulative (August 28, 2016 to February 11, 2017)
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 # %
<5 173 0 26 147 <5 >1358 <5 577 781 51 >1409 x%
5-19 150 0 29 121 9 >1598 <5 829 769 55 >1653 x%
20-44 193 0 46 147 12 2457 8 1345 1104 59 2516 16%
45-64 181 0 50 131 7 2642 11 1381 1250 65 2707 17%
65+ 674 0 158 516 14 7803 5 3704 4094 99 7902 49%
Total 1371 0 309 1,062 >42 15863 29 7836 7998 329 16192 100%
PercentageTable 1 - Footnote 2 97% 0% 23% 77% 3% 98% 0% 49% 50% 2%    

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 06, 3.3% of visits to healthcare professionals were due to influenza-like illness, up from 2.3% in the previous week.

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17, week 6

Number of Sentinels Reporting Week 06: 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 1.08%
50 1.30%
51 1.73%
52 2.83%
1 1.96%
2 2.22%
3 1.92%
4 2.02%
5 2.31%
6 3.25%

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.

Influenza Outbreak Surveillance

In week 06, 67 laboratory confirmed influenza outbreaks were reported (10 more than the previous week). Among the reported outbreaks: 43 in long-term care (LTC) facilities, four in hospitals and 20 in institutional or community (other) settings. Of the outbreaks with known strains or subtypes, 14 were due to influenza A(H3N2), 35 were due to influenza A(UnS) and two were due to influenza B. An additional two outbreaks due to ILI were reported in schools.

To date this season, 736 outbreaks have been reported and the majority (66%) have occurred in LTC facilities. Compared to the same period in the most recent previous A(H3N2) predominant season (2014-15), 1,304 outbreaks were reported, of which 74% occurred in LTC facilities.

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote 1 by report week, Canada, 2016-17, week 6
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 14 3
50 4 15 4
51 5 32 13
52 7 65 18
1 15 84 22
2 13 83 24
3 19 44 9
4 8 39 8
5 13 33 11
6 4 43 20

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 06, 269 influenza-associated hospitalizations were reported by participating provinces and territories, down from  336 reported in the previous week*. Influenza A accounted for nearly all of hospitalizations (98%). The largest proportion of hospitalizations were among adults aged 65+ (68%). A total of ten intensive care unit (ICU) admissions and 12 deaths were reported in week 06.

To date this season, 3,662 hospitalizations have been reported, of which 99% were due to influenza A. Among cases for which the subtype of influenza A was reported, almost all (2087/2102) were influenza A(H3N2). Adults 65+ accounted for 69% of the hospitalizations. A total of 131 ICU admissions and greater than 144 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 6
Age Groups (years) Cumulative (August 28, 2016 to Feb. 11 2017)
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
0-4 257 9 266 (7%) 7  5% <5 1%
5-19 158 8 166 (5%) 9 6% <5 1%
20-44 198 <5 >198 (5%) 11  8% 0 0%
45-64 487 5 492 (13%) 41  31% 25 17%
65+ 2508 29 2537 (69%) 63  48% 119 81%
Total 3608 >51 >3659 (100%) 131 100% >144  100%

Sentinel Hospital Influenza Surveillance

Pediatric Influenza Hospitalizations and Deaths

In week 06, 32 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. All cases were due to influenza A. The number of hospitalizations reported in week 06 is below the six year average for the same time period (Figure 7).

To date this season, 344 laboratory-confirmed influenza-associated pediatric hospitalizations were reported by the IMPACT network. Children aged 0-23 months accounted for approximately 38% of hospitalizations. Influenza A accounted for 94% (n=323) of the reported hospitalizations, of which 39% (n=127) were influenza A(H3N2) and the remainder were A(UnS). Additionally, 58 intensive care unit (ICU) admissions have been reported, of which the largest proportion (29%) was reported in children 0-23 months. A total of 34 ICU cases reported at least one underlying condition or comorbidity. No deaths have been reported this season.

In 2014-15, the previous influenza A(H3N2)-predominant season, there were 503 hospitalizations, 57 ICU admissions and less than five deaths reported as of week 06.

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 6

Figure 6
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 59
6-23 mo 73
2-4 yr 90
5-9 yr 59
10-16 yr 63

Figure 7 – Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, 2016-17, week 6

Figure 7

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 3 1 0 3
44 6 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 20 24 4 47
51 17 35 4 71
52 38 47 7 92
1 48 37 3 75
2 28 36 6 60
3 38 37 2 67
4 43 34 5 47
5 29 39 10 57
6 32 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 06, 72 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 of cases (78%) occurred in adults aged 65+.

To date this season, 829 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by CIRN. All but eight hospitalized cases were due to influenza A. Adults aged 65+ accounted for 77% of hospitalizations. To date, approximately 41 intensive care unit (ICU) admissions have been reported. A total of 29 ICU cases reported at least one underlying condition or comorbidity. The median age of patients admitted to the ICU was 67 years. Approximately 26 deaths have been reported this season, the majority in adults aged 65+. The median age of reported deaths was 84 years.

Figure 8 - Cumulative numbers of adult hospitalizations (≥20 years of age) with influenza by type and age-group reported by CIRN, Canada, 2016-17, week 6

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 66
45-64 yr 122
65+ yr 641

Figure 9 – Percentage of hospitalizations, ICU admissions and deaths with influenza by age-group (≥20 years of age) reported by CIRN, Canada 2016-17, week 6

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 ≥ 829) ICU admissions (n ≥ 41) Deaths (n= 26)
- Supressed due to small values
20-44 8.0% 7.0% 0.0%
45-64 14.7% 25.0% 4.0%
65+ 77.3% 68.2% 96.3%

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 669 influenza viruses [622 A(H3N2), 11 A(H1N1), 36 influenza B].  All but one influenza A virus (n=632) and all 36 influenza B viruses characterized were antigentically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Nineteen influenza B viruses were similar to the strain included only in the quadrivalent vaccine.

Table 3 – Influenza strain characterizations, Canada, 2016-17, week 6
Strain Characterization ResultsTable 3 - Footnote 1 Count Description
Influenza A (H3N2)
Antigenically
A/Hong Kong/4801/2014-like
200 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
421

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 200 influenza A (H3N2) viruses that underwent HI testing determined that 159 viruses belonged to genetic group 3C.2a and 30 viruses belonged to genetic group 3C.3a. Sequencing is pending for the remaining 11 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-likeTable 3 - Footnote 4
1

Viruses antigenically similar to A/Indiana/10/2011, a candidate H3N2v vaccine virus.

Influenza A (H1N1)
A/California/7/2009-like 11 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)
17 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)
19 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 438 influenza viruses for resistance to oseltamivir and zanamivir and 139 influenza viruses for resistance to amantadine. All viruses were sensitive to oseltamivir and zanamivir. All 139 influenza A viruses were resistant to amantadine 
(Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, 2016-17, week 6
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
A (H3N2) 393 0 (0%) 393 0 (0%) 130 130 (100%)
A (H3N2v) 1 0 (0%) 1 0 (0%) 1 1 (100%)
A (H1N1) 10 0 (0%) 9 0 (0%) 8 8 (100%)
B 34 0 (0%) 35 0 (0%) N/ATable 4 - Footnote * N/ATable 4 - Footnote *
TOTAL 438 0 (0%) 438 0 (0%) 139 139 (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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