FluWatch report: May 20, 2018 to June 23, 2018 (Week 21-25)

Overall Summary
  • Influenza activity is at interseasonal levels across the country.
  • The majority of regions in Canada are reporting no influenza activity.
  • All indicators of influenza activity are either near or below average for this time of year.
  • Influenza A is the most common influenza virus circulating in Canada.
  • The next report will be published July 27, 2018.
  • Influenza and other respiratory viruses will be monitoried weekly and results will be reported every Thursday in the Respiratory Virus Detections in Canada Report.
  • For more information on the flu, see our Flu (influenza) web page.

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Organization:

Public Health Agency of Canada

Date published: 2018-06-23

Related Topics

Influenza/Influenza-like Illness Activity (geographic spread)

In week 25, seven regions across five provinces and territories reported sporadic activity. The majority of regions (39) reported no activity.

Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, week 2018-25
Figure 1. Text version below.
Figure 1 - Text description
Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, week 2018-20
Influenza Surveillance Region Activity Level
Newfoundland - Central  No Activity
Newfoundland - Eastern  No Activity
Grenfell Labrador No Activity
Newfoundland - Western  No Activity
Prince Edward Island No Activity
Nova Scotia - Central (Zone 4) No Activity
Nova Scotia - Western (Zone 1) No Activity
Nova Scotia - Northern (Zone 2) No Activity
Nova Scotia - Eastern (Zone 3) No Activity
New Brunswick - Public Health Region 1 Sporadic
New Brunswick - Public Health Region 2 No Activity
New Brunswick - Public Health Region 3 No Activity
New Brunswick - Public Health Region 4 No Activity
New Brunswick - Public Health Region 5 No Activity
New Brunswick - Public Health Region 6 No Activity
New Brunswick - Public Health Region 7 No Activity
Nord-est Québec Sporadic
Québec et Chaudieres-Appalaches No Activity
Centre-du-Québec Sporadic
Montréal et Laval Sporadic
Ouest-du-Québec No Activity
Montérégie  No Activity
Ontario - Central East No Activity
Ontario - Central West No Activity
Ontario - Eastern No Activity
Ontario - North East No Activity
Ontario - North West  No Activity
Ontario - South West  No Activity
Ontario - Toronto Sporadic
Manitoba - Interlake-Eastern  No Data
Manitoba - Northern Regional No Data
Manitoba - Prairie Mountain No Data
Manitoba - South No Data
Manitoba - Winnipeg No Data
Saskatchewan - North  No Activity
Saskatchewan - Central No Activity
Saskatchewan - South No Activity
Alberta - North Zone No Activity
Alberta - Edmonton No Activity
Alberta - Central Zone  No Activity
Alberta - Calgary Sporadic
Alberta - South Zone  No Activity
British Columbia - Interior No Activity
British Columbia - Fraser  No Activity
British Columbia - Vancouver Coastal No Activity
British Columbia - Vancouver Island No Activity
British Columbia - Northern No Activity
Yukon No Activity
Northwest Territories - North No Data
Northwest Territories - South No Data
Nunavut - Baffin No Activity
Nunavut - Kivalliq Sporadic
Nunavut - Kitimeot No Activity

Laboratory-Confirmed Influenza Detections

In weeks 21-25, a total of 196 laboratory detections of influenza were reported and influenza A accounted for 69% of influenza detections. In week 25, the percentage of tests positive for influenza was 0.6%. Overall, laboratory detections of influenza are below expected levels for this time of year.

For data on other respiratory virus detections, see the Respiratory Virus Detections in Canada Report.

Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, 2017-35 to 2018-25

Figure 1. Text version below.

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

To date this season, 64,309 laboratory-confirmed influenza detections have been reported, of which 56% have been influenza A. Influenza A(H3N2) has been the most common subtype detected this season, representing 90% of subtyped influenza A 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 2 - Text description
Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2017-18
Report Week A(Unsubtyped) A(H3N2) A(H1N1)pdm09 Influenza B
35 3 20 6 5
36 7 28 1 3
37 7 14 13 4
38 18 31 3 5
39 18 53 1 8
40 24 41 1 5
41 32 50 0 11
42 27 73 1 15
43 44 107 3 21
44 52 114 3 30
45 71 153 7 47
46 113 187 13 75
47 157 272 13 112
48 259 417 33 190
49 370 544 16 274
50 523 633 16 473
51 800 864 51 719
52 1,105 856 33 1,008
1 1,836 925 60 1,539
2 1,987 808 49 1,730
3 1,649 870 80 1,912
4 1,675 632 57 1,802
5 1,664 542 54 2,125
6 1,819 506 49 2,383
7 1,754 405 63 2,443
8 1,642 279 51 2,354
9 1,437 325 51 2,057
10 1,023 265 80 1,714
11 807 246 73 1,387
12 551 189 76 966
13 458 183 40 767
14 436 143 49 661
15 370 127 57 500
16 302 84 29 322
17 214 62 35 238
18 153 51 44 129
19 89 7 13 81
20 51 5 12 38
21 40 7 14 27
22 22 11 11 14
23 8 5 1 8
24 8 1 3 6
25 4 1 1 7

 

Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, weeks 2017-35 to 2018-25
Figure 3. Text version below.
Figure 3 - Text description
Figure 3 - Weekly and cumulative numbers of positive influenza specimens by type/subtype and province, Canada, 2017-18
Reporting provincesTable Figure 3 - Footnote 1 Week (May 20, 2018 to June 23, 2018) Cumulative (August 27, 2017 to June 23, 2018)
Influenza A B Influenza A B A & B
A Total A(H1N1)pdm09 A(H3N2) A(UnS)Table Figure 3 - Footnote 3 B Total A Total A(H1N1)pdm09 A(H3N2) A(UnS)Table Figure 3 - Footnote 3 B Total Total
BC 7 2 5 0 0 2,484 518 1,520 446 3,021 5,505
AB 22 16 2 4 7 5,699 278 3,996 1,425 3,394 9,093
SK 0 0 0 0 0 1,730 69 1132 529 1,716 3,446
MB 3 2 0 1 2 1,137 22 378 737 639 1,776
ON 29 7 13 9 6 6,347 300 3,480 2,567 4,835 11,182
QC 37 0 0 37 18 15,510 0 0 15,510 12,350 27,860
NB 29 3 5 21 23 1,713 36 249 1,428 1,280 2,993
NS 8 0 0 8 1 563 0 0 563 302 865
PE 0 0 0 0 0 146 8 134 4 171 317
NL 1 0 0 1 1 479 0 3 476 436 915
YT 0 0 0 0 0 76 7 48 21 43 119
NT 0 0 0 0 0 130 4 126 0 56 186
NU 0 0 0 0 2 46 6 40 0 6 52
Canada 136 30 25 81 60 36,060 1,248 11,106 23,706 28,249 64,309
PercentageTable figure 3 Footnote 2 64% 22% 18% 60% 36% 56% 3% 31% 66% 44% 100%
Table Figure 3 - Footnote 1

Specimens from NT, YT, and NU are sent to reference laboratories in other provinces.

Return to Table Figure 3 - Footnote 1 referrer*

Table Figure 3 - Footnote 2

Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections.

Return to Table Figure 3 - Footnote 2 referrer

Table Figure 3 - Footnote 3

Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available.

Return to first Table Figure 3 - Footnote 3 referrer

Discrepancies in values in Figures 2 and 3 may be attributable to differing data sources.

Cumulative data includes updates to previous weeks.

To date this season, detailed information on age and type/subtype has been received for 55,015 laboratory-confirmed influenza cases (Table 1). Adults 65 years of age and older represent the largest proportion of cases overall (48%), and among cases of influenza A(H3N2) (57%) and influenza B (46%). Adults aged 20-64 represent 32% of cases overall and 30% of influenza A(H3N2) and 34% of influenza B cases. Although much smaller in numbers (1,022), the majority of influenza A(H1N1)pdm09 cases are among adults less than 65 years of age, with adults aged 20-64 and children 0-19 years accounting for 52% and 32% of cases respectively.

Table 1 - Cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reporting, Canada, weeks 2017-35 to 2018-25
Age groups (years) Cumulative (August 27, 2017 to June 23, 2018)
Influenza A B Influenza A and B
A Total A(H1N1) pdm09 A(H3N2) A (UnS)1 Total # %
0-4 3,356 181 690 2,485 1,625 4,981 9%
5-19 2,571 146 724 1,701 3,001 5,572 10%
20-44 4,617 281 1,432 2,904 3,059 7,676 14%
45-64 4,997 251 1,641 3,105 5,128 10,125 18%
65+ 15,643 163 5,844 9,636 11,018 26,661 49%
Total 31,184 1,022 10,331 19,831 23,831 55,015 100%
Table 1 Notes
Table 1 Note 1

UnS: unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available

Return to table 1 note 1 referrer

 

Syndromic/Influenza-like Illness Surveillance

Healthcare Practitioners Sentinel Syndromic Surveillance

In week 25, 0.6% of visits to healthcare professionals were due to influenza-like illness (ILI).

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2017-35 to 2018-25

Number of Sentinels Reporting in Week 25: 158

Figure 4. Text version below.

The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2012-13 to 2016-17

Figure 4 - Text description
Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2017-18
Semaine de déclaration 2017-18 Moyenne Min Max
35 0.4% 0.8% 0.5% 1.2%
36 0.5% 0.8% 0.7% 1.0%
37 0.7% 0.9% 0.7% 1.0%
38 0.7% 1.1% 1.0% 1.4%
39 1.1% 1.1% 0.9% 1.4%
40 1.3% 1.3% 0.9% 1.6%
41 1.7% 1.4% 0.9% 2.4%
42 1.2% 1.4% 1.0% 1.9%
43 1.6% 1.3% 1.0% 1.5%
44 1.5% 1.3% 0.9% 1.6%
45 1.8% 1.3% 1.2% 1.5%
46 1.7% 1.6% 1.0% 2.0%
47 2.2% 1.5% 1.1% 1.9%
48 2.8% 1.6% 0.8% 2.1%
49 1.7% 1.5% 1.0% 2.5%
50 2.2% 2.3% 1.3% 3.7%
51 2.6% 2.5% 1.6% 4.1%
52 4.0% 4.5% 1.7% 7.1%
1 4.4% 3.7% 1.7% 5.2%
2 2.8% 3.0% 1.1% 4.5%
3 2.9% 2.5% 1.3% 3.6%
4 3.1% 2.4% 1.7% 3.5%
5 4.0% 2.7% 2.0% 4.4%
6 3.5% 2.7% 2.1% 3.3%
7 3.4% 2.4% 1.7% 3.0%
8 3.1% 2.3% 1.9% 2.7%
9 2.8% 2.2% 1.8% 2.7%
10 1.7% 2.1% 1.8% 2.7%
11 1.2% 2.1% 1.7% 2.7%
12 1.6% 1.8% 1.1% 2.7%
13 1.7% 1.7% 1.2% 2.6%
14 0.9% 1.8% 1.3% 2.4%
15 1.3% 1.6% 0.9% 1.9%
16 1.3% 1.5% 1.0% 1.9%
17 1.5% 1.5% 0.9% 2.2%
18 1.3% 1.2% 0.8% 1.6%
19 1.4% 1.3% 1.0% 1.7%
20 0.9% 1.2% 0.9% 1.4%
21 0.8% 0.9% 0.3% 1.3%
22 0.9% 0.8% 0.6% 1.0%
23 0.7% 0.9% 0.6% 1.2%
24 0.9% 0.7% 0.4% 1.0%
25 0.6% 1.2% 0.5% 1.6%
26   0.8% 0.4% 1.4%
27   0.8% 0.4% 1.5%
28   1.0% 0.6% 1.9%
29   0.8% 0.5% 1.1%
30   0.5% 0.3% 0.7%
31   0.9% 0.3% 1.4%
32   1.0% 0.6% 1.6%
33   1.2% 0.4% 2.1%
34   0.7% 0.5% 0.9%

Participatory Syndromic Surveillance

FluWatchers is a participatory ILI surveillance system that relies on weekly voluntary submissions of syndromic information from Canadians across Canada. Click here to learn more about the FluWatchers program.

FluWatchers surveillance has ended for the 2017-18 season.

If you are interested in becoming a FluWatcher for the 2018-19 season, sign up today.

Influenza Outbreak Surveillance

In weeks 21-25, two influenza A outbreaks in long term care facilities were reported.

To date this season, 1,797 influenza/ILI outbreaks have been reported, of which 1,107 (62%) occurred in LTC facilities. Among the 1,535 outbreaks for which the influenza type/subtype was reported, 845 (55%) were associated with influenza A and 618 (40%) were associated with influenza B, and 72 (5%) were associated with a mix of A and B.

Figure 5 - Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2017-35 to 2018-25

Figure 5. Text version below.
Figure 5 - Text description
Figure 5 - Overall number of new laboratory-confirmed influenza outbreaks by report week, Canada, 2017-18
Report week Hospitals Long Term Care Facilities Other
35 0 0 0
36 0 1 0
37 0 0 0
38 0 2 0
39 0 1 1
40 1 0 0
41 0 0 1
42 0 2 1
43 3 1 1
44 0 1 0
45 3 1 4
46 0 2 5
47 0 2 5
48 9 11 7
49 4 14 12
50 9 31 16
51 11 48 28
52 5 72 23
1 12 110 38
2 18 99 48
3 14 84 45
4 13 65 24
5 9 55 19
6 10 77 31
7 11 58 28
8 8 60 22
9 8 84 16
10 12 46 10
11 2 44 12
12 8 32 10
13 5 30 8
14 9 18 8
15 3 31 10
16 1 10 4
17 0 6 3
18 3 4 4
19 2 2 1
20 0 1 0
21 0 1 0
22 0 1 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

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 5,155 influenza-associated hospitalizations were reported by participating provinces and territoriesfigure 6 note 1. Among the hospitalizations, 3,433 (67%) were associated with influenza A, and 3,368 cases (65%) were in adults 65 years of age or older.

Additionally, 588 ICU admissions and 303 deaths have been reported to date. Adults aged 65 years of age or older accounted for the greatest proportion of ICU cases (44%), followed by adults aged 20-64 (40%). Adults aged 65 years of age or older accounted the majority of deaths (85%).

Figure 6 - Cumulative numbers of hospitalizations by age-group reported by participating provinces and territoriesfigure 6 note 1, weeks 2017-35 to 2018-25

Figure 6. Text version below.
Figure 6 - Text description
Figure 6 - Cumulative numbers of hospitalizations by age-group reported by participating provinces and territories, 2017-18
Age group Total
0-4 325
5-19 238
20-44 341
45-64 883
65+ 3368
Figure 6 note 1

Influenza-associated hospitalizations are reported by NL, PE, NS, NB, MB, AB, YT and NT. Only hospitalizations that require intensive medical care are reported by SK.

Return to figure 6 note 1 referrer

Pediatric Influenza Hospitalizations and Deaths

In weeks 21-25, eight laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. The number of weekly reported hospitalizations are below the seven-season average.

To date this season, 1,078 pediatric hospitalizations have been reported by the IMPACT network, 675 (62%) of which were associated with influenza A. Children 0-23 months  accounted for the largest proportion of influenza A hospitalizations (39%). Among the 403 hospitalizations due to influenza B, children 5-9 years accounted for the largest proportion of cases (32%).

Additionally, 195 ICU admissions and nine deaths have been reported to date. Children aged 0-23 months accounted for the greatest proportion of ICU cases (31%), followed by children aged 5-9 years (25%). Among the ICU cases with available information, 63% were due to influenza A and approximately 43% had no reported previous or concurrent medical conditions. All but one reported deaths were among children over the age of two.

Figure 7 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, weeks 2017-35 to 2018-25

Figure 7. Text version below.
Figure 7 - Text description
Figure 7 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, 2017-18
Age Group Total
0-5 mo 112
6-23 mo 251
2-4 yr 270
5-9 yr 264
10-16 yr 181

Figure 8 - Number of pediatric (≤16 years of age) hospitalizations reported by the IMPACT network, by week, Canada, weeks 2017-35 to 2018-25

Figure 8. Text version below.

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2016-17

Figure 8 - Text description
Figure 8 - Number of pediatric (≤16 years of age) hospitalizations reported by IMPACT sentinel hospital network, by week, Canada, 2017-18
Report week 2017-18 Average Min Max
35 0 0 0 0
36 1 0 0 1
37 0 0 0 2
38 1 0 0 2
39 2 1 0 3
40 0 0 0 2
41 3 1 0 2
42 1 1 0 4
43 7 1 0 3
44 1 3 1 6
45 4 3 2 4
46 7 5 1 13
47 13 4 0 9
48 17 9 2 23
49 23 15 3 28
50 25 23 4 47
51 38 32 4 72
52 60 47 7 92
1 57 40 5 75
2 38 35 4 62
3 52 38 4 67
4 93 35 7 47
5 70 40 11 59
6 73 38 15 79
7 83 40 17 120
8 72 47 25 139
9 68 50 13 153
10 60 48 17 135
11 57 41 18 118
12 33 33 13 89
13 28 32 14 67
14 30 24 12 56
15 14 23 13 56
16 9 20 10 41
17 13 16 8 37
18 9 14 4 28
19 5 10 5 18
20 2 10 4 19
21 4 5 2 10
22 1 4 1 8
23 1 2 0 5
24 2 2 0 5
25   1 0 3
26   1 0 3
27   1 0 2
28   1 0 2
29   0 0 2
30   0 0 1
31   0 0 0
32   0 0 1
33   0 0 0
34   1 0 2

Influenza Strain Characterizations

During the 2017-18 influenza season, the National Microbiology Laboratory (NML) has characterized 3,819 influenza viruses [1,563 A(H3N2), 330 A(H1N1)pdm09 and 1,926 B viruses] that were received from Canadian laboratories

Antigenic Characterization

Among influenza viruses characterized by hemagglutination inhibition (HI) assay during the 2017-18 season, most viruses were antigenically similar to the cell-culture propagated reference strains recommended by WHO.

Table 2 - Influenza antigenic strain characterizations, Canada, weeks 2017-35 to 2018-25
Strain Characterization Results Count Description
Influenza A (H3N2)
A/Hong Kong/4801/2014-like 308 Viruses antigenically similar to A/Hong Kong/4801/2014, the A(H3N2) component of the 2017-18 Northern Hemisphere's trivalent and quadrivalent vaccine.
Reduced titer to A/Hong Kong/4801/2014 101 These A(H3N2) viruses reacted poorly with antisera raised against cell-propagated A/Hong Kong/4801/2014, suggesting some antigenic differences.
Influenza A (H1N1)pdm09
A/Michigan/45/2015-like 330 Viruses antigenically similar to A/Michigan/45/2015, the A(H1N1)pdm09 component of the 2017-18 Northern Hemisphere's trivalent and quadrivalent influenza vaccine.
Influenza B
B/Brisbane/60/2008-like
(Victoria lineage)
26 Viruses antigenically similar to B/Brisbane/60/2008. B/Brisbane/60/2008 is the influenza B component of the 2017-18 Northern Hemisphere’s trivalent and quadrivalent influenza vaccine.
Reduced titer to B/Brisbane/60/2008
(Victoria lineage)
55 These B/Victoria lineage viruses reacted poorly with antisera raised against cell-propagated B/Brisbane/60/2008, suggesting some antigenic differences.
B/Phuket/3073/2013-like
(Yamagata lineage)
1,845 Viruses antigenically similar to B/Phuket/3073/2013, the additional influenza B component of the 2017-18 Northern Hemisphere quadrivalent influenza vaccine.

Genetic Characterization of A(H3N2) viruses

During the 2017-18 season, 1,154 A(H3N2) viruses did not grow to sufficient titers for antigenic characterization by HI assay. Therefore, genetic characterization was performed to determine to which genetic group they belong. Sequence analysis showed that 1,033 A(H3N2) viruses belonged to genetic group 3C.2a, 118 viruses belonged to subclade 3C.2a1 and three viruses belonged to the clade 3C.3a.

Additionally, of the 409 influenza A(H3N2) viruses that were antigenically characterized, 279 belonged to genetic group 3C.2a and 27 viruses belonged to subclade 3C.2a1. The 101 viruses that showed reduced titer to A/Hong Kong/4801/2014 belonged to genetic clade 3C.3a. Sequencing is pending for the remaining two isolates.

A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A/H3N2 component of the 2017-18 Northern Hemisphere influenza vaccine.

Genetic Characterization of Influenza B viruses

Among the viruses characterized antigenically as having reduced titer to ferret antisera produced against cell-propagated B/Brisbane/60/2008, sequence analysis showed that 54 viruses had a two amino acid deletion in the HA gene. Sequencing is pending for the remaining virus isolate.

Antiviral Resistance

During the 2017-18 season, the National Microbiology Laboratory (NML) has tested 1,728 influenza viruses for resistance to oseltamivir and 1,724 viruses for resistance to zanamivir. All but three viruses (1 A(H1N1)pdm09,1 A(H3N2) and 1 influenza B) were sensitive to oseltamivir and all but two influenza B viruses were sensitive to zanamivir (Table 3). The A(H1N1)pdm09 virus resistant to oseltamivir had a H275Y mutation.

Table 3 - Antiviral resistance by influenza virus type and subtype, Canada, weeks 2017-35 to 2018-25
Virus type and subtype Oseltamivir Zanamivir
# tested # resistant (%) # tested # resistant (%)
A (H3N2) 594 1 (0.2%) 590 0 (0%)
A (H1N1) 271 1 (0.4%) 271 0 (0%)
B 863 1 (0.1%) 863 2 (0.2%)
TOTAL 1728 3 (0.2%) 1724 2 (0.1%)

Note: Since the 2009 pandemic, all circulating influenza A viruses have been resistant to amantadine, and it is therefore not currently recommended for use in the treatment of influenza. During the 2017-18 season, all but eight influenza A viruses that were tested for resistance to amantadine were resistant.

The FluWatch report is compiled from a number of data sources. Surveillance information contained in this report is a reflection of the surveillance data available to FluWatch at the time of production. Delays in reporting of data may cause data to change retrospectively.

Influenza/Influenza-like Illness (ILI) Activity

Influenza/ILI activity levels, as represented on the map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, primary care consultations for ILI and reported outbreaks. ILI data may be reported through sentinel physicians, emergency room visits or health line telephone calls, and the determination of an increase is based on the assessment of the provincial/territorial epidemiologist. Maps from previous weeks, including any retrospective updates, are available in the mapping feature found in the Weekly Influenza Reports.

Influenza/ILI Activity Level definitions

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†
3 = Localized:
(1) evidence of increased ILI*; (2) lab confirmed influenza detection(s); (3) outbreaks in schools, hospitals, residential
institutions and/or other types of facilities occurring in less than 50% of the influenza surveillance region†
4 = Widespread:
(1) evidence of increased ILI*; (2) lab confirmed influenza detection(s);(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 region†;

* More than just sporadic as determined by the provincial/territorial epidemiologist. †Influenza surveillance regions within the province or territory as defined by the provincial/territorial epidemiologist

† Influenza surveillance regions within the province or territory as defined by the provincial/territorial epidemiologist

Laboratory-Confirmed Influenza Detections

Provincial, regional and some hospital laboratories report the weekly number of tests and detections of influenza and other respiratory viruses. Provincial public health laboratories submit demographic information for cases of influenza. This case-level data represents a subset of influenza detections reported through aggregate reporting. Specimens from NT, YT, and NU are sent to reference laboratories in the provinces for testing. Cumulative data includes updates to previous weeks. Discrepancies in values in Figures 2 and 3 may be attributable to differing data sources.

Syndromic/Influenza-like Illness Surveillance

FluWatch maintains a network of primary care practitioners who report the weekly proportion of ILI cases seen in their practice. Independent sentinel networks in BC, AB, and SK compile their data for reporting to FluWatch. Not all sentinel physicians report every week.

Definition of 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 years of age, gastrointestinal symptoms may also be present. In patients under 5 or 65 years and older, fever may not be prominent.

Influenza Outbreak Surveillance

Outbreaks of influenza or ILI are reported from all provinces and territories, according to the definitions below. However, reporting of outbreaks of influenza/ILI from different types of facilities differs between jurisdictions. All provinces and territories with the exception of NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals.

Outbreak definitions:

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.

Hospitals and residential institutions:

two or more cases of ILI within a seven-day period, including at least one laboratory-confirmed case of influenza. Residential institutions include but are 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 of influenza; i.e. closed communities.

Serious Outcome Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

Influenza-associated hospitalizations and deaths are reported by 8 Provincial and Territorial Ministries of Health (excluding BC, NU, ON and QC). The hospitalization or death does not have to be attributable to influenza, a positive laboratory test is sufficient for reporting. Only hospitalizations that require intensive medical care are reported by SK.

Due to changes in participating provinces and territories, comparisons to previous years should be done with caution.

Pediatric Influenza Hospitalizations and Deaths

The Immunization Monitoring Program Active (IMPACT) network reports the weekly number of hospitalizations with influenza among children admitted to one of the 12 participating paediatric hospitals in 8 provinces. These represent a subset of all influenza-associated pediatric hospitalizations in Canada.

Influenza Strain Characterizations and Antiviral Resistance

Provincial public health laboratories send a subset of influenza virus isolates to the National Microbiology Laboratory for strain characterization and antiviral resistance. These represent a subset of all influenza detections in Canada and the proportion of isolates of each type and subtype is not necessarily representative of circulating viruses.

Antigenic strain characterization data reflect the results of hemagglutination inhibition (HI) testing compared to the reference influenza strains recommended by WHO. Genetic strain characterization data are based on analysis of the sequence of the viral hemagglutinin (HA) gene.
Antiviral resistance testing is conducted by phenotypic and genotypic methods on influenza virus isolates submitted to the National Microbiology Laboratory. All isolates are tested for oseltamivir and zanamivir and a subset are tested for resistance to amantadine.

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).

This report is available on the Government of Canada Influenza webpage.

We would like to thank all the FluWatch surveillance partners who are participating in this year's influenza surveillance program.

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