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FluWatch report: December 31, 2017 to January 6, 2018 (week 1)

Overall, influenza activity in Canada is high and continues to increase. Most indicators of influenza activity increased in week 01, and are in the higher range of expected levels for this time of year.

The majority of influenza detections continue to be A(H3N2), although the proportion of detections that are influenza B has been increasing steadily

Influenza B is circulating much earlier than usual this season. The number of influenza B detections remains substantially greater this season compared to previous years.

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

For more information on the flu, see our

Flu(influenza)

web page.

On this page

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 definitions for the 2017-2018 season

Influenza/Influenza-like Illness Activity (geographic spread)

In week 01, an increasing number of regions reported localized or widespread influenza activity; nine regions (BC(2), ON(3), QC(3) and PE(1)) reported widespread activity, and 27 regions (BC(2), AB(4), SK(1), MB (4), ON(4), QC(3), NB(5), NS(3) and NT(1)) reported localized activity.

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Organization:

Public Health Agency of Canada

Date published:

2018-01-12

Flu (influenza)

Influenza surveillance

Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, week 2018-01

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 2018-01

Influenza Surveillance Region

Activity Level

Newfoundland - Central

Sporadic

Newfoundland - Eastern

Sporadic

Grenfell Labrador

Sporadic

Newfoundland - Western

No Activity

Prince Edward Island

Widespread

Nova Scotia - Central (Zone 4)

Localized

Nova Scotia - Western (Zone 1)

Localized

Nova Scotia - Northern (Zone 2)

Sporadic

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

Localized

New Brunswick - Public Health Region 7

Localized

Nord-est Québec

Localized

Québec et Chaudieres-Appalaches

Localized

Centre-du-Québec

Widespread

Montréal et Laval

Widespread

Ouest-du-Québec

Widespread

Montérégie

Localized

Ontario - Central East

Widespread

Ontario - Central West

Localized

Ontario - Eastern

Localized

Ontario - North East

Localized

Ontario - North West

Widespread

Ontario - South West

Widespread

Ontario - Toronto

Localized

Manitoba - Interlake-Eastern

Localized

Manitoba - Northern Regional

Sporadic

Manitoba - Prairie Mountain

Localized

Manitoba - South

Localized

Manitoba - Winnipeg

Localized

Saskatchewan - North

Sporadic

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

Sporadic

British Columbia - Fraser

Widespread

British Columbia - Vancouver Coastal

Widespread

British Columbia - Vancouver Island

Localized

British Columbia - Northern

Localized

Yukon

Sporadic

Northwest Territories - North

Sporadic

Northwest Territories - South

Localized

Nunavut - Baffin

No Activity

Nunavut - Kivalliq

No Activity

Nunavut - Kitimeot

No Activity

Laboratory-Confirmed Influenza Detections

In week 01, both influenza A and B detections continued to increase although the rate of increase in influenza A detections was smaller compared to influenza B. The slowing of influenza A detections may indicate that we are approaching the peak of the season for influenza A, at the national level. However, the number of influenza B detections increased 52% compared to the previous week to1,529 in week 01, which is the highest weekly value observed over the past seven seasons.

The proportion of tests positive for influenza increased slightly from 28% in week 52 to 30% in week 01. The proportion of influenza detections that are influenza B has been increasing steadily since week 42. In week 01, 64% of detections were influenza A and 36% influenza B.

The number (2,732) and percentage (19.3%) of influenza A detections for week 01 are within the range of expected levels for this time of year. The number (1,529) and percentage of tests (10.8%) positive for influenza B in week 01 continue to be well above expected levels. Influenza B is circulating much earlier than usual this season. Twenty times the number of influenza B detections have been reported this season compared to the same period during the past seven seasons. 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 2018-01

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 2018-01

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

1130

828

33

1008

1

1731

857

144

1529

To date this season, 15,572 laboratory-confirmed influenza detections have been reported, of which 71% 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 2018-01

Figure 3 - Text Description

Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, weeks 2017-35 to 2018-01

Reporting

provinces

Table Figure 3 - Footnote

1

Week (December 17, 2017 to January 6, 2018)

Cumulative (August 27, 2017 to January 6, 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

198

31

114

53

218

747

114

432

201

645

1392

AB

441

11

329

101

223

4388

71

3236

1081

1457

5845

SK

109

1

60

48

58

823

20

537

266

206

1029

MB

186

0

31

155

13

521

6

216

299

31

552

ON

344

8

206

130

222

1109

58

649

402

586

1695

QC

1,190

0

0

1,190

617

2919

0

0

2919

1391

4310

NB

80

80

0

0

15

310

80

61

169

37

347

NS

23

0

0

23

8

62

0

0

62

10

72

PE

11

2

9

0

13

40

2

38

0

24

64

NL

12

7

0

5

96

21

7

3

11

101

122

YT

1

0

1

0

4

6

0

6

0

33

39

NT

10

0

10

0

3

84

0

84

0

6

90

NU

1

0

1

0

0

14

0

14

0

1

15

Canada

2606

140

761

1705

1490

11044

358

5276

5410

4528

15572

Percentage

Table Figure 3 - Footnote

2

64%

5%

29%

65%

36%

71%

3%

48%

49%

29%

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 14,038 laboratory-confirmed influenza cases (Table 1). Among all influenza cases with reported age and type/subtype information, 47% 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 52% of cases, compared to 41% and 56% of cases reported in the same period in the 2016-17 and 2014-15 season, respectively. 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 (41%), followed by adults 45-64 years of age (23%).

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 2018-01

Age groups (years)

Cumulative (August 27, 2017 to January 6, 2018)

Influenza A

B

Influenza A and B

A Total

A(H1) pdm09

A(H3)

A (UnS)

Table 1 Footnote

1

Total

#

%

0-4

842

48

389

405

211

1053

8%

5-19

868

42

429

397

563

1431

10%

20-44

1710

70

809

831

631

2341

17%

45-64

1719

56

826

837

897

2616

19%

65+

5001

28

2642

2331

1596

6597

47%

Total

10140

244

5095

4801

3898

14038

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 01, 4.7% of visits to healthcare professionals were due to influenza-like illness (ILI); an increase compared to the previous week, and above the 5-year average.

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2017-35 to 2018-01

Number of Sentinels Reporting in Week 1: 116

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 2018-01

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

2.8%

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

4.7%

3.7%

1.7%

5.2%

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 01, 1,406 participants reported to FluWatchers, of which 5% reported symptoms of cough and fever, and 22% of these consulted a healthcare professional. Among participants who reported cough and fever, 84% reported days missed from work or school, resulting in a combined total of 186 missed days of work or school.

Table 2 - Summary of influenza-like illness symptoms reported by participating Canadians, Canada, week 2018-01

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

1406

5%

22%

84%

186

Influenza Outbreak Surveillance

In week 01, the number of reported laboratory-confirmed outbreaks of influenza increased compared to the previous week. In week 01, 148 new influenza outbreaks were reported: 98 in long-term care facilities, 12 in hospitals, and 38 in other settings. Among the 120 outbreaks with influenza type/subtype reported, 44 (37%) were associated with influenza B, and 73 were associated with influenza A, of which 20 were influenza A(H3N2) and 53 influenza A(unsubtyped). Three outbreaks were associated with a mix of influenza A and B.

To date this season, 486 influenza/ILI outbreaks have been reported, of which 282 (58%) occurred in LTC facilities. Among the 403 outbreaks for which the influenza type/subtype was reported, 286 were associated with influenza A (of which 153 were A(H3N2), 132 were A(unsubtyped) and one was A(H1N1)pdm09), 101 were associated with influenza B, and 16 were associated with a mix of A and B. Compared to recent influenza A(H3N2) seasons at week 01, 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 2018-01

Figure 5 - Text Description

Figure 5 - Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2017-35 to 2018-01

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

67

23

1

12

98

38

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 01, 128 influenza-associated hospitalizations were reported by participating provinces and territories

Footnote

1

. 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, 1,850 influenza-associated hospitalizations have been reported, 83% of which were associated with influenza A, and 1,254 cases (68%) were in adults 65 years of age or older. To date, 162 ICU admissions and 54 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 2018-01

Figure 6 - Text Description

Figure 6 - Cumulative numbers of hospitalizations by age-group reported by participating provinces and territories, weeks 2017-35 to 2018-01

Age Group

Total

0-4 yr

119

5-19 yr

66

20-44 yr

109

45-64 yr

302

65+ yr

1254

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 01, the number of laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations reported by the Immunization Monitoring Program Active (IMPACT) network decreased compared to the previous week. In week 01, 46 hospitaliations were reported, of which 25 (54%) were due to influenza A. The proportion of cases associated with influenza B has been increasing over the past three weeks. The number of weekly hospitalizations has been above the seven-season average since week 45.

To date this season, 253 pediatric hospitalizations have been reported by the IMPACT network, 177 (70%) of which were associated with influenza A. Forty-one ICU admissions and fewer than five deaths have been reported. Compared to recent influenza A(H3N2) seasons at week 01, the cumulative number of 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 2018-01

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 2018-01

Age Group

Total

0-5 mo

29

6-23 mo

63

2-4 yr

64

5-9 yr

52

10-16 yr

47

Figure 8 - Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, weeks 2017-35 to 2018-01

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 2018-01

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

12

4

0

9

48

18

9

2

23

49

24

15

3

28

50

26

23

4

47

51

39

32

4

72

52

59

47

7

92

1

46

40

5

75

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 351 influenza viruses [229 A(H3N2), 26 A(H1N1)pdm09 and 96 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 2018-01

Strain Characterization Results

Count

Description

Influenza A (H3N2)

A/Hong Kong/4801/2014-like

54

Viruses antigenically similar to A/Hong Kong/4801/2014, the A(H3N2) component of the 2017-18 Northern Hemisphere's

trivalent

and

quadrivalent

vaccine.

Influenza A (H1N1)

A/Michigan/45/2015-like

26

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)

1

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)

5

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)

90

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, 175 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 143 A(H3N2) viruses belonged to genetic group 3C.2a, 31 viruses belonged to subclade 3C.2a1 and one virus belonged to the clade 3C.3a.

Additionally, of the 54 influenza A(H3N2) viruses that were characterized antigenically as similar to A/Hong Kong/4801/2014, 45 belonged to genetic group 3C.2a and eight viruses belonged to subclade 3C.2a1. Sequencing is pending for the remaining one virus.

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 five viruses had a two amino acids deletion in the HA gene.

Antiviral Resistance

During the 2017-18 season, the National Microbiology Laboratory (NML) has tested 353 influenza viruses for resistance to oseltamivir and zanamivir. All viruses were sensitive to these neuraminidase inhibitors (Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, weeks 2017-35 to 2018-01

Virus type and subtype

Oseltamivir

Zanamivir

# tested

# resistant (%)

# tested

# resistant (%)

A (H3N2)

230

0 (0%)

230

0 (0%)

A (H1N1)

27

0 (0%)

27

0 (0%)

B

96

0 (0%)

96

0 (0%)

TOTAL

353

0 (0%)

353

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

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2018-01-19