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FluWatch report: January 7, 2018 to January 13, 2018 (week 2)

Overall, influenza activity in Canada remains high.

Most indicators have slowed their increase, remained similar, or declined compared to the previous week, suggesting that we may be nearing the peak of the season at the national level.

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

The majority of influenza detections continue to be A(H3N2), although 37% of detections were influenza B in week 02.

Influenza B began 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 Surveillance System Description and Definitions, 2017-18

Influenza/Influenza-like Illness Activity (geographic spread)

In week 02, a similar number of regions reported localized or widespread influenza activity compared to the previous week. Among the 48 regions reporting data for week 02, nine regions (BC(2), ON(5), and QC(2)) reported widespread activity, and 24 regions (BC(1), AB(5), SK(2), ON(2), QC(4), NB(5), NS(1), NL(2), PE(1) and NT(1)) reported localized activity.

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Organization:

Public Health Agency of Canada

Date published:

2018-01-19

Flu (influenza)

Influenza surveillance

Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, week 2018-02

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 2018-02

Influenza Surveillance Region

Activity Level

Newfoundland - Central

No Activity

Newfoundland - Eastern

Localized

Grenfell Labrador

No Activity

Newfoundland - Western

Localized

Prince Edward Island

Localized

Nova Scotia - Central (Zone 4)

Sporadic

Nova Scotia - Western (Zone 1)

Sporadic

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

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

Localized

Montérégie

Localized

Ontario - Central East

Widespread

Ontario - Central West

Widespread

Ontario - Eastern

Localized

Ontario - North East

Widespread

Ontario - North West

Widespread

Ontario - South West

Widespread

Ontario - Toronto

Localized

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

Sporadic

Saskatchewan - Central

Localized

Saskatchewan - South

Localized

Alberta - North Zone

Localized

Alberta - Edmonton

Localized

Alberta - Central Zone

Localized

Alberta - Calgary

Localized

Alberta - South Zone

Localized

British Columbia - Interior

Widespread

British Columbia - Fraser

Widespread

British Columbia - Vancouver Coastal

Sporadic

British Columbia - Vancouver Island

Localized

British Columbia - Northern

Sporadic

Yukon

Sporadic

Northwest Territories - North

Sporadic

Northwest Territories - South

Localized

Nunavut - Baffin

Sporadic

Nunavut - Kivalliq

Sporadic

Nunavut - Kitimeot

Sporadic

Laboratory-Confirmed Influenza Detections

In week 02, 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. The increase in the number of influenza B detections slowed slightly, increasing 11% compared to the previous week, to1,713 in week 02. Influenza B detections to date are higher than has been observed over the past seven seasons.

The proportion of tests positive for influenza increased slightly from 29% in week 01 to 30% in week 02. The proportion of influenza detections that are influenza B has been increasing since week 43. In week 02, 63% of detections were influenza A and 37% influenza B.

The number (2,952) and percentage (19.0%) of influenza A detections for week 02 are within the range of expected levels for this time of year. The number (1,713) and percentage of tests (11.0%) positive for influenza B in week 02 continue to be well above expected levels for this time of year. 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 average over the same period during the past seven seasons. However, the percentage of tests positive for influenza B at week 02 is within the range of levels usually observed in March-April. 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 2018-02

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 2018-02

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

1839

928

60

1538

2

2163

745

44

1713

To date this season, 20,349 laboratory-confirmed influenza detections have been reported, of which 69% have been influenza A.

Influenza A(H3N2)

has been the most common subtype detected this season, representing 95% 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 2018-02

Figure 3 - Text Description

Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, weeks 2017-35 to 2018-02

Reporting

provinces

Table Figure 3 - Footnote

1

Week (January 7, 2018 to January 13, 2018)

Cumulative (August 27, 2017 to January 13, 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

343

29

145

169

312

1113

143

577

393

992

2105

AB

191

4

148

39

109

4617

77

3411

1129

1597

6214

SK

98

6

73

19

41

1032

28

704

300

276

1308

MB

237

0

40

197

27

756

6

293

457

58

814

ON

462

4

222

236

403

1632

63

899

670

1023

2655

QC

1261

0

0

1261

738

4180

0

0

4180

2129

6309

NB

154

0

23

131

20

464

0

84

380

57

521

NS

50

0

0

50

7

112

0

0

112

17

129

PE

2

0

2

0

15

42

2

40

0

39

81

NL

17

0

0

17

7

33

0

3

30

17

50

YT

6

0

2

4

0

12

0

8

4

33

45

NT

4

0

4

0

1

95

0

95

0

7

102

NU

1

0

1

0

0

15

0

15

0

1

16

Canada

2826

43

660

2123

1680

14103

319

6129

7655

6246

20349

Percentage

Table Figure 3 - Footnote

2

63%

2%

23%

75%

37%

69%

2%

43%

54%

31%

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 17,495 laboratory-confirmed influenza cases (Table 1). Among all influenza cases with reported age and type/subtype information, 49% 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, compared to 43% and 58% 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 (45%), followed by adults

45-64 years

of age (23%).

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 2018-02

Age groups (years)

Cumulative (August 27, 2017 to January 13, 2018)

Influenza A

B

Influenza A and B

A Total

A(H1) pdm09

A(H3)

A (UnS)

Table 1 Footnote

1

Total

#

%

0-4

1005

59

429

517

291

1296

7%

5-19

953

45

461

447

654

1607

9%

20-44

1983

83

890

1010

784

2767

16%

45-64

2074

66

937

1071

1187

3261

19%

65+

6214

35

3048

3131

2350

8564

49%

Total

12229

288

5765

6176

5266

17495

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 02, 3.2% 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 2018-02

Number of Sentinels Reporting in Week 02: 144

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 2018-02

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%

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 02, 1,443 participants reported to FluWatchers, of which 4% reported symptoms of cough and fever, and 20% of these consulted a healthcare professional. Among participants who reported cough and fever, 74% reported days missed from work or school, resulting in a combined total of 135 missed days of work or school.

Table 2 - Summary of influenza-like illness symptoms reported by participating Canadians, Canada, week 2018-02

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

1443

4%

20%

74%

135

Influenza Outbreak Surveillance

In week 02, the number of reported laboratory-confirmed outbreaks of influenza increased slightly compared to the previous week. In week 02, 163 new influenza outbreaks were reported: 97 in long-term care facilities, 18 in hospitals, and 48 in other settings. In addition, one ILI outbreak was reported in a school. Among the 149 outbreaks with influenza type/subtype reported, 71 (48%) were associated with influenza B, and 73 were associated with influenza A, of which 17 were influenza A(H3N2) and 56 influenza A(unsubtyped). Five outbreaks were associated with a mix of influenza A and B.

To date this season, 663 influenza/ILI outbreaks have been reported, of which 392 (59%) occurred in LTC facilities. Among the 566 outbreaks for which the influenza type/subtype was reported, 364 were associated with influenza A (of which 175 were A(H3N2), 188 were A(unsubtyped) and one was A(H1N1)pdm09), 179 were associated with influenza B, and 23 were associated with a mix of A and B. Compared to recent influenza A(H3N2) seasons at week 02, 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 2018-02

Figure 5 - Text Description

Figure 5 - Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2017-35 to 2018-02

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

97

48

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 02, 133 influenza-associated hospitalizations were reported by participating provinces and territories

Footnote

1

, a similar number compared to the previous week. 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, 2,168 influenza-associated hospitalizations have been reported, 81% of which were associated with influenza A, and 1,480 cases (68%) were in adults 65 years of age or older. To date, 202 ICU admissions and 82 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 2018-02

Figure 6 - Text Description

Figure 6 - Cumulative numbers of hospitalizations by age-group reported by participating provinces and territories, weeks 2017-35 to 2018-02

Age Group

Total

0-4 yr

134

5-19 yr

72

20-44 yr

133

45-64 yr

349

65+ yr

1480

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 02, 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 02, 40 hospitaliations were reported, of which 25 (63%) 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, 303 pediatric hospitalizations have been reported by the IMPACT network, 209 (69%) of which were associated with influenza A. Forty-eight ICU admissions and fewer than five deaths have been reported. Compared to the cumulative number of pediatric hospitalizations reported up to week 02 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 2018-02

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 2018-02

Age Group

Total

0-5 mo

38

6-23 mo

75

2-4 yr

81

5-9 yr

58

10-16 yr

51

Figure 8 - Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, weeks 2017-35 to 2018-02

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 2018-02

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

40

35

4

62

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 482 influenza viruses

[299 A(H3N2),

34 A(H1N1)pdm09

and

149 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 2018-02

Strain Characterization Results

Count

Description

Influenza A (H3N2)

A/Hong Kong/4801/2014-like

72

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

34

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)

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)

142

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,

227 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

185 A(H3N2)

viruses belonged to genetic

group 3C.2a,

41 viruses belonged to

subclade 3C.2a1

and one virus belonged to the

clade 3C.3a.

Additionally, of the 72 influenza A(H3N2) viruses that were characterized antigenically as similar to A/Hong Kong/4801/2014, 57 belonged to genetic

group 3C.2a

and 10 viruses belonged to

subclade 3C.2a1.

The virus that showed reduced titer belonged to genetic

clade 3C.3a.

Sequencing is pending for the remaining 5 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 423 influenza viruses for resistance to oseltamivir and 424 viruses for resistance to 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 2018-02

Virus type and subtype

Oseltamivir

Zanamivir

# tested

# resistant (%)

# tested

# resistant (%)

A (H3N2)

255

0 (0%)

255

0 (0%)

A (H1N1)

32

0 (0%)

33

0 (0%)

B

136

0 (0%)

136

0 (0%)

TOTAL

423

0 (0%)

424

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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2018-01-19