FluWatch report: January 1 to January 7, 2017 (week 1)

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Organization: Public Health Agency of Canada

Date published: 2017-01-13

  • Overall, greater numbers of laboratory detections, outbreaks and hospitalizations were reported in week 1 compared to previous weeks suggesting that Canada is nearing peak influenza activity.
  • A total of 2,639 positive influenza detections were reported in week 1, an increase from the previous week. Influenza A(H3N2) continues to be the most common subtype detected.
  • One hundred and six confirmed influenza outbreaks were reported in week 1, with the majority occurring in long-term care facilities and due to influenza A(H3N2).
  • The number of hospitalizations, ICU admissions and deaths reported by participating provinces and territories sharply increased from week 52 to week 1; the majority of hospitalizations and all deaths reported in week 1 were in adults.
  • Influenza activity started early this season, but so far activity has been lower than the 2014-15 season when A(H3N2) was the predominant subtype.
  • For more information on the flu, see our Flu (influenza) web page.

In week 1, a total of six regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 17 regions across eight provinces and territories. Localized activity was reported in 18 regions across nine provinces (PE, NS, ON, QC, MB, SK, AB, BC, and NU). Widespread activity was reported in eight regions (one region in QC,four regions in AB and three regions in BC). 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 1
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 1, a total of six regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 17 regions across eight provinces and territories. Localized activity was reported in 18 regions across nine provinces (PE, NS, ON, QC, MB, SK, AB, BC, and NU). Widespread activity was reported in eight regions (one region in QC,four regions in AB and three regions in BC).

The percentage of tests positive for influenza increased from 23.5% in week 52 to 24% in week 1. Compared to the previous influenza A(H3N2)-predominant season in 2014-15, the percent positive in week 1 (24%) was lower than the percent positive reported in week 53 of the 2014-15 season (35%). 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 1
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
52 921 1064 <5 33
1517 1256 <5 35
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 01, 2,727 positive influenza tests were reported, up from 1,948 tests reported in week 52. To date, a total of 8,976 laboratory confirmed influenza detections have been reported. Influenza A(H3N2) is the most common subtype detected, representing 99% of subtyped influenza A detections (5015/5039). 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 1
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 (January 1, 2017 to January 7, 2017) Cumulative (August 28, 2016 to January 7, 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 390 0 107 283 5 1117 2 725 390 25 1142
AB 421 0 339 82 7 2105 7 1982 116 31 2136
SK 87 0 45 42 1 581 0 250 331 9 590
MB 10 0 8 2 2 27 0 25 2 9 36
ON 873 1 633 239 6 2432 14 1803 615 39 2471
QC 841 0 37 804 14 2192 0 115 2076 72 2264
NB 25 0 9 16 0 50 1 18 31 3 53
NS 14 0 0 14 0 41 0 1 40 0 41
PE 11 0 11 0 0 19 0 19 0 0 19
NL 7 0 7 0 0 29 0 25 4 4 33
YT 11 0 3 8 0 175 0 135 40 1 176
NT 2 0 2 0 0 8 0 8 0 0 8
NU 0 0 0 0 0 6 0 6 0 1 7
Canada 2692 1 1201 1490 35 8782 24 5112 3645 194 8976
PercentageTable Figure 3 - Footnote 2 99% 0% 45% 55% 1% 98% 0% 58% 42% 2% 100%

To date this season, detailed information on age and type/subtype has been received for 6,879 laboratory confirmed influenza cases. Adults aged 65+ were the age group that accounted for the largest proportion of reported influenza cases (>45%) and the largest proportion of influenza A (H3N2) cases. Compared to the cases reported in the 2014-15 season at week 53, adults aged 65+ account for a smaller proportion of cases this season (approximately 45% in 2016-17 compared to 62% in 2014-15). Adults aged 45-64 account for a greater proportion of cases this season (approximately 46% in 2016-17 compared to 63% 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, Week 1
Age groups (years) Weekly (January 1 to January 7, 2017) Cumulative (August 28, 2016 to January 7, 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 # %
<5 132 0 36 96 <5 >537 <5 262 275 36 >573 x%
5-19 60 0 23 37 <5 >750 <5 485 265 27 >777 x%
20-44 197 0 70 127 <5 1,127 5 698 424 24 1,151 17%
45-64 248 0 81 167 <5 1,163 8 663 492 20 1,183 17%
65+ 877 0 182 695 8 >3,156 <5 1,495 1,661 33 >3,189 x%
Total 1,514 0 392 1,122 22 6,739 19 3,603 3,117 140 6,879 100%
PercentageTable 1 - Footnote 2 99% 0% 26% 74% 1% 98% 0% 53% 46% 2%    

Healthcare Professionals Sentinel Syndromic Surveillance

In week 1, 2.0% of visits to healthcare professionals were due to ILI, down from week 52 where 2.8% of visits were due to ILI.

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

Number of Sentinels Reporting Week 1: 95

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 2.84%
1 2.00%

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 01, 106 laboratory confirmed influenza outbreaks were reported: 69 in long-term care (LTC) facilities, 15 in hospitals and 22 in institutional or community settings. Of the outbreaks with known strains or subtypes: 105 outbreaks were due to influenza A of which 24 were due to influenza A(H3N2) (four in hospitals, 11 in LTC facilities and nine in institutional or community settings), 81 were due to influenza A(UnS) (nine in hospitals, 51 in LTC facilities and 21 in institutional or community settings). One outbreak was due to influenza B.

To date this season, 333 outbreaks have been reported and the majority (68%) have occurred in LTC facilities. In comparison at week 53 in the 2014-15 season, the previous influenza A(H3N2)-predominant season, 623 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 1
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 14 4
51 5 31 13
52 7 61 17
1 15 69 22
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 1, 445 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote *. Influenza A accounted for all but three of the reported hospitalizations. A total of 15 ICU admissions and 13 deaths were reported in week 1. Adults aged 65+ accounted for the largest proportion of hospitalizations (75%). All deaths in week 1 were reported in adults.

To date this season, 1436 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 (858/861) were influenza A(H3N2). Adults 65+ accounted for approximately 69% of the hospitalizations. Sixty intensive care unit (ICU) admissions and 36 deaths have been reported. The majority of deaths (78%) 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 1
Age Groups (years) Cumulative (August 28, 2016 to Jan. 7 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 95 5 >100 (7%) <5 x% 0  0%
5-19 66 <5 >66 (x%) <5 x% <5 x%
20-44 78 <5 >78 (x%) <5 x% 0 0%
45-64 187 <5 >187 (x%) 20 33% <5 x%
65+ 990 7 997 (69%) 28 47% 28 x%
Total 1416 20 1436 (100%) 60 100% >35 100%

Pediatric Influenza Hospitalizations and Deaths

In week 01, a total of 46 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. All but one case was due to influenza A. The number of hospitalizations reported in week 1 is comparable to the number of hospitalizations reported for week 01 in the previous six seasons.

To date this season, 171 laboratory-confirmed influenza-associated pediatric hospitalizations were reported by the IMPACT network. Children aged 0-2 years accounted for approximately 41% of hospitalizations. Influenza A accounted for 92% (n=157) of the reported hospitalizations, of which 48% (n=75) were influenza A(H3N2) and the remainder were A(UnS). Additionally, 26 intensive care unit (ICU) admissions have been reported, of which the largest proportion (31%) was reported in children 10-16 years. No deaths have been reported this season.

Compared to 2014-15, the previous influenza A(H3N2)-predominant season, where 358 hospitalizations were reported as of week 53, there has 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 1
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 35
6-23 mo 35
2-4 yr 42
5-9 yr 28
10-16 yr 30
Figure 7 - Number of pediatric (≤16 years of age) hospitalizations reported by IMPACT sentinel hospital network, by week, Canada, 2016-17, Week 1
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 20 24 4 47
51 18 35 4 71
52 36 47 7 92
1 46 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 1, a total of 171 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN). All but one case was due to influenza A and the greatest proportion of cases (82%) occurred in adults aged 65+.

To date this season, 375 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by CIRN. All but three hospitalized cases were due to influenza A. Adults aged 65+ accounted for 75% of hospitalizations. To date, greater than eighteen ICU admissions and seven 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 1
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 22
45-64 yr 70
65+ yr 283
Figure 9 - Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group (≥16 year of age), Canada 2015-16, Week 1
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= >206) ICU admissions (n= <9) Deaths (n= <5)
- Supressed due to small values
20-44 5.9% 12.0% 0.0%
45-64 18.7% 16.0% 0.0%
65+ 75.5% 72.2% 100.0%

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 217 influenza viruses [189 A(H3N2), 10 A(H1N1), 18 influenza B]. All but one influenza A virus (n=198) and nine influenza B viruses characterized were antigentically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Nine influenza B viruses were similar to the strain which is included only in the quadirvalent vaccine.

Table 3 - Influenza strain characterizations, Canada, 2016-17, Week 1
Strain Characterization ResultsTable 3 - Footnote 1 Count Description
Influenza A (H3N2)
Antigenically
A/Hong Kong/4801/2014-like
68 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
120

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 62 influenza A (H3N2) viruses that underwent HI testing determined that 48 viruses belonged to genetic group 3C.2a and 10 viruses belonged to genetic group 3C.3a. Sequencing is pending for the remaining four 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 10 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)
9 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)
9 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 224 influenza viruses for resistance to oseltamivir and zanamivir and 116 influenza viruses for resistance to amantadine. All viruses were sensitive to oseltamivir and zanamivir. All 116 influenza A viruses were resistant to amantadine (Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, 2016-17, Week 1
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
A (H3N2) 196 0 (0%) 196 0 (0%) 109 109 (100%)
A (H3N2v) 1 0 (0%) 1 0 (0%) 1 1 (100%)
A (H1N1) 9 0 (0%) 9 0 (0%) 6 6 (100%)
B 18 0 (0%) 18 0 (0%) N/ATable 4 - Footnote * N/ATable 4 - Footnote *
TOTAL 224 0 (0%) 224 0 (0%) 116 116 (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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