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FluWatch report: January 14, 2018 to January 20, 2018 (week 3)

Overall, influenza activity in Canada remains high but there is some indication that activity is starting to slow down.

Most indicators remain in the higher range of expected levels for this time of year.

In week 3, the percentage of laboratory test positive for influenza B continued to increase while the percentage of laboratory test positive for influenza A remained stable.

The majority of influenza detections continue to be A(H3N2), although 40% of detections were influenza B in week 03.

To date this season, the majority of lab confirmations, hospitalizations and deaths have been among adults 65 years of age and older.

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Influenza/ILI Activity (geographic spread)

Laboratory Confirmed Influenza Detections

Syndromic/Influenza-like Illness Surveillance

Influenza Outbreak Surveillance

Severe Outcomes Influenza Surveillance

Influenza Strain Characterizations

Antiviral Resistance

Provincial and International Influenza Reports

FluWatch Surveillance System Description and Definitions, 2017-18

Influenza/Influenza-like Illness Activity (geographic spread)

In week 03, a similar number of regions reported localized or widespread influenza activity compared to the previous week. Among the 53 regions reporting data for week 03, 11 regions (BC(2), ON(4), QC(4), and PE (1)) reported widespread activity, and 23 regions (BC(1), AB(4), SK(2), MB(1), ON(3), QC(2), NB(4), NS(3), NL(2), and NT(1)) reported localized activity.

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Organization:

Public Health Agency of Canada

Date published:

2018-01-26

Flu (influenza)

Influenza surveillance

Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, week 2018-03

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

Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, week 2018-03

Influenza Surveillance Region

Activity Level

Newfoundland - Central

Sporadic

Newfoundland - Eastern

Localized

Grenfell Labrador

No Activity

Newfoundland - Western

Localized

Prince Edward Island

Widespread

Nova Scotia - Central (Zone 4)

Localized

Nova Scotia - Western (Zone 1)

Localized

Nova Scotia - Northern (Zone 2)

No Activity

Nova Scotia - Eastern (Zone 3)

Localized

New Brunswick - Public Health Region 1

Localized

New Brunswick - Public Health Region 2

Localized

New Brunswick - Public Health Region 3

Localized

New Brunswick - Public Health Region 4

Sporadic

New Brunswick - Public Health Region 5

Sporadic

New Brunswick - Public Health Region 6

Sporadic

New Brunswick - Public Health Region 7

Localized

Nord-est Québec

Localized

Québec et Chaudieres-Appalaches

Widespread

Centre-du-Québec

Widespread

Montréal et Laval

Widespread

Ouest-du-Québec

Widespread

Montérégie

Localized

Ontario - Central East

Widespread

Ontario - Central West

Widespread

Ontario - Eastern

Localized

Ontario - North East

Localized

Ontario - North West

Widespread

Ontario - South West

Widespread

Ontario - Toronto

Localized

Manitoba - Interlake-Eastern

Sporadic

Manitoba - Northern Regional

Sporadic

Manitoba - Prairie Mountain

Sporadic

Manitoba - South

Sporadic

Manitoba - Winnipeg

Localized

Saskatchewan - North

Localized

Saskatchewan - Central

Localized

Saskatchewan - South

Sporadic

Alberta - North Zone

Sporadic

Alberta - Edmonton

Localized

Alberta - Central Zone

Localized

Alberta - Calgary

Localized

Alberta - South Zone

Localized

British Columbia - Interior

Localized

British Columbia - Fraser

Widespread

British Columbia - Vancouver Coastal

Sporadic

British Columbia - Vancouver Island

Widespread

British Columbia - Northern

Sporadic

Yukon

Sporadic

Northwest Territories - North

Sporadic

Northwest Territories - South

Localized

Nunavut - Baffin

No Activity

Nunavut - Kivalliq

No Activity

Nunavut - Kitimeot

Sporadic

Laboratory-Confirmed Influenza Detections

In week 03, the percentage of tests positive for influenza increased slightly from 29% in week 02 to 31% in week 03. This increase is mainly driven by influenza B activity: the percentage of test positive for influenza B increased from 11% in week 02 to 13% in week 03. Influenza B detections to date are higher than has been observed over the past seven seasons.

The percentage of test positive for influenza A remained stable at 18% since week 02. The stablization of influenza A detections over the past two weeks may indicate that the peak of the season for influenza A detections occurred in week 01.

The number (2,533) and percentage (18%) of influenza A detections for week 03 are within the range of expected levels for this time of year. The number (1,835) and percentage of tests (13%) positive for influenza B in week 03 continue to be well above 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, Canada, weeks 2017-35 to 2018-03

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

.

Figure 2 - Text Description

Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, weeks 2017-35 to 2018-03

Report Week

A(Unsubtyped)

A(H3)

A(H1)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

1105

856

33

1008

1

1836

925

60

1539

2

1987

807

49

1730

3

1764

701

68

1835

To date this season, 24,749 laboratory-confirmed influenza detections have been reported, of which 67% have been influenza A. Influenza A(H3N2) has been the most common subtype detected this season, representing 94% 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 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, weeks 2017-35 to 2018-03

Figure 3 - Text Description

Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, weeks 2017-35 to 2018-03

Reporting

provinces

Table Figure 3 - Footnote

1

Week (January 14, 2018 to January 20, 2018)

Cumulative (August 27, 2017 to January 20, 2018)

Influenza A

B

Influenza A

B

A & B

Total

A

Total

A

(H1)pdm09

A

(H3)

A(UnS)

Table Figure 3 - Footnote

3

B

Total

A

Total

A

(H1)pdm09

A

(H3)

A(UnS)

Table Figure 3 - Footnote

3

B

Total

BC

410

54

269

87

330

1401

197

846

358

1322

2723

AB

201

4

143

54

173

4852

82

3583

1187

1787

6639

SK

76

2

63

11

49

1161

32

809

320

353

1514

MB

141

0

19

122

19

897

6

311

580

77

974

ON

462

8

247

207

404

2083

75

1172

836

1426

3509

QC

1119

0

0

1119

776

5299

0

0

5299

2905

8204

NB

85

0

0

85

68

549

0

84

465

125

674

NS

40

0

0

40

13

152

0

0

152

30

182

PE

5

0

5

0

27

47

2

45

0

66

113

NL

9

0

0

9

2

42

0

3

39

19

61

YT

10

1

3

6

2

18

1

11

6

35

53

NT

11

1

10

0

6

110

1

109

0

15

125

NU

5

0

5

0

1

21

0

21

0

2

12

Canada

2574

70

764

1740

1870

16632

396

6994

9242

8162

24794

Percentage

Table Figure 3 - Footnote

2

58%

3%

30%

68%

42%

67%

2%

42%

56%

33%

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 21,369 laboratory-confirmed influenza cases (Table 1). Among all influenza cases with reported age and type/subtype information, 50% have been reported in adults 65 years of age and older. Among cases of influenza A(H3N2), adults 65 years of age and older represented 53% of cases. Cases of influenza B this season were distributed more evenly across all age-groups, but the largest proportion of cases was still among adults 65 years of age and older (46%), followed by adults 45-64 years of age (22%).

Table 1 - Weekly and cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reporting, Canada, weeks 2017-35 to 2018-03

Age groups (years)

Cumulative (August 27, 2017 to January 20, 2018)

Influenza A

B

Influenza A and B

A Total

A(H1) pdm09

A(H3)

A (UnS)

Table 1 Footnote

1

Total

#

%

0-4

1208

64

469

675

391

1599

7%

5-19

1117

55

512

550

808

1925

9%

20-44

2323

101

1001

1221

971

3294

15%

45-64

2436

88

1059

1289

1522

3958

19%

65+

7454

47

3475

3932

3139

10593

50%

Total

14538

355

6516

7667

6831

21369

100%

Table 1 Footnote 1

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

Return to table 1 footnote

1

referrer

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 03, 3% of visits to healthcare professionals were due to influenza-like illness (ILI); a decrease compared to the previous week, and slightly above the 5-year average.

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2017-35 to 2018-03

Number of Sentinels Reporting in Week 03: 153

The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2012-13 to 2017-18

Figure 4 - Text Description

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2017-35 to 2018-03

Report week

2017-18

Average

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

2.7%

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

4.7%

3.7%

1.7%

5.2%

2

3.2%

3.0%

1.1%

4.5%

3

3.0%

2.5%

1.3%

3.6%

Participatory Syndromic Surveillance

FluWatchers is a participatory ILI surveillance system that relies on weekly voluntary submissions of syndromic information from Canadians across Canada.

In week 03, 1,469 participants reported to FluWatchers, of which 5% reported symptoms of cough and fever, and 31% of these consulted a healthcare professional. Among participants who reported cough and fever, 90% reported days missed from work or school, resulting in a combined total of 223 missed days of work or school.

Table 2 - Summary of influenza-like illness symptoms reported by participating Canadians, Canada, week 2018-03

Number of Participants Reporting

Percentage participants reporting Cough and Fever

Percentage of participants with cough and fever who consulted a healthcare professional

Percentage of participants with cough and fever who reported missed days from work or school

Number of missed days from work or school

1469

5%

31%

90%

223

Influenza Outbreak Surveillance

In week 03, the number of reported laboratory-confirmed outbreaks of influenza decreased compared to the previous week. In week 03, 137 new influenza outbreaks were reported: 78 in long-term care facilities, 14 in hospitals, and 45 in other settings. In addition, one ILI outbreak was reported in a school. Among the 129 outbreaks with influenza type/subtype reported, 52 (40%) were associated with influenza B, and 72 were associated with influenza A, of which 22 were influenza A(H3N2) and 50 influenza A(unsubtyped). Five outbreaks were associated with a mix of influenza A and B.

To date this season, 802 influenza/ILI outbreaks have been reported, of which 471 (59%) occurred in LTC facilities. Among the 696 outbreaks for which the influenza type/subtype was reported, 436 were associated with influenza A (of which 197 were A(H3N2), 238 were A(unsubtyped) and one was A(H1N1)pdm09), 232 were associated with influenza B, and 28 were associated with a mix of A and B. Compared to recent influenza A(H3N2) seasons at week 03, the number of cumulative outbreaks reported this season has been greater than during the 2016-17 and 2012-13 seasons, and lower compared to the 2014-15 season.

Figure 5 - Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2017-35 to 2018-03

Figure 5 - Text Description

Figure 5 - Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2017-35 to 2018-03

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

69

23

1

12

109

38

2

18

98

48

3

14

78

45

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 03, 182 influenza-associated hospitalizations were reported by participating provinces and territories1. In keeping with the early influenza activity this season, the number of hospitalizations is considerably elevated relative to the same period in the previous two seasons.

To date this season, 2,643 influenza-associated hospitalizations have been reported, 80% of which were associated with influenza A, and 1,814 cases (69%) were in adults 65 years of age or older. To date, 241 ICU admissions and 110 deaths have been reported.

Figure 6 - Cumulative numbers of hospitalizations by age-group reported by participating provinces and territories

figure 6 note

1

, weeks 2017-35 to 2018-03

Figure 6 - Text Description

Figure 6 - Cumulative numbers of hospitalizations by age-group reported by participating provinces and territories, weeks 2017-35 to 2018-03

Age Group

Total

0-4 yr

158

5-19 yr

92

20-44 yr

166

45-64 yr

413

65+ yr

1814

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 week 03, the number of laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations reported by the Immunization Monitoring Program Active (IMPACT) network increased compared to the previous week. In week 03, 49 hospitaliations were reported, of which 40 (82%) were due to influenza A. The number of weekly hospitalizations has been above the seven-season average since week 45, but following seasonal patterns.

To date this season, 354 pediatric hospitalizations have been reported by the IMPACT network, 250 (71%) of which were associated with influenza A. Fifty-eight ICU admissions and fewer than five deaths have been reported. Compared to the cumulative number of pediatric hospitalizations reported up to week 03 during recent influenza A(H3N2)-dominant seasons, the cumulative number of pediatric hospitalizations reported this season has been greater than the 2016-17 season, but below the 2014-15 and 2012-13 seasons.

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 2018-03

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, weeks 2017-35 to 2018-03

Age Group

Total

0-5 mo

44

6-23 mo

86

2-4 yr

96

5-9 yr

72

10-16 yr

56

Figure 8 - Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, weeks 2017-35 to 2018-03

Figure 8 - Text Description

Figure 8 - Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, weeks 2017-35 to 2018-03

Report Week

2017-2018

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

8

5

1

13

47

13

4

0

9

48

16

9

2

23

49

23

15

3

28

50

26

23

4

47

51

39

32

4

72

52

61

47

7

92

1

55

40

5

75

2

41

35

4

62

3

49

38

4

67

Figure 8 Footnote 1

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2017-18

Return to figure 8 note

1

referrer

Influenza Strain Characterizations

During the 2017-18 influenza season, the National Microbiology Laboratory (NML) has characterized 583 influenza viruses [318 A(H3N2), 42 A(H1N1)pdm09 and 223 B viruses] that were received from Canadian laboratories.

Antigenic Characterization

Among influenza viruses characterized by hemagglutination inhibition assay during the

2017-18 season,

most viruses were antigenically similar to the cell-culture propagated reference strains recommended by WHO.

Table 3 - Influenza antigenic strain characterizations, Canada, weeks 2017-35 to 2018-03

Strain Characterization Results

Count

Description

Influenza A (H3N2)

A/Hong Kong/4801/2014-like

83

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

1

These A(H3N2) viruses reacted poorly with antisera raised against cell-propagated A/Hong Kong/4801/2014, suggesting some antigenic differences.

Influenza A (H1N1)

A/Michigan/45/2015-like

42

Viruses antigenically similar to A/Michigan/45/2015, the A(H1N1) component of the 2017-18 Northern Hemisphere's

trivalent

and

quadrivalent

influenza vaccine.

Influenza B

B/Brisbane/60/2008-like

(Victoria lineage)

5

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)

6

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)

212

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, 234 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 191 A(H3N2) viruses belonged to genetic group 3C.2a, 42 viruses belonged to subclade 3C.2a1 and one virus belonged to the clade 3C.3a.

Additionally, of the 83 influenza A(H3N2) viruses that were characterized antigenically as similar to A/Hong Kong/4801/2014, 60 belonged to genetic group 3C.2a and 11 viruses belonged to subclade 3C.2a1. The virus that showed reduced titer belonged to genetic clade 3C.3a. Sequencing is pending for the remaining 12 virus 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 all six viruses had a two amino acid deletion in the HA gene.

Antiviral Resistance

During the 2017-18 season, the National Microbiology Laboratory (NML) has tested 521 influenza viruses for resistance to oseltamivir and 516 viruses for resistance to zanamivir. All but one of the A(H1N1) viruses were sensitive to oseltamivir and all viruses were sensitive to zanamivir (Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, weeks 2017-35 to 2018-03

Virus type and subtype

Oseltamivir

Zanamivir

# tested

# resistant (%)

# tested

# resistant (%)

A (H3N2)

299

0 (0%)

295

0 (0%)

A (H1N1)

39

1 (2.6%)

39

0 (0%)

B

183

0 (0%)

182

0 (0%)

TOTAL

521

1 (0.2%)

516

0 (0%)

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, the subset of influenza A viruses that were tested for resistance to amantadine were resistant.

Provincial and International Influenza Reports

Provincial Influenza Reports

Alberta - Influenza Surveillance Report

British Columbia - Influenza Surveillance

Manitoba - Seasonal Influenza Reports

New Brunswick - Influenza Surveillance Reports

Newfoundland and Labrador - Surveillance and Disease Reports

Nova Scotia - Respiratory Watch Report

Ontario - Respiratory Pathogen Bulletin

Prince Edward Island - Influenza Summary

Saskatchewan - Influenza Reports

Québec - Flash Grippe

International Influenza Reports

Australia - Influenza Surveillance Report

European Centre for Disease Prevention and Control - Surveillance reports and disease data on seasonal influenza

New Zealand - Influenza Weekly Update

Public Health England - Weekly national flu reports

Pan-American Health Organization - Influenza Situation Report

United States Centres for Disease Control and Prevention - Weekly Influenza Surveillance Report

World Health Organization - Influenza update

World Health Organization - FluNet

FluWatch Surveillance System Description and Definitions, 2017-18

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. For a description of FluWatch surveillance components and definitions, see

System Description and Definitions

.

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).

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

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2018-01-26