FluWatch report: June 23, 2019 to July 20, 2019 (Weeks 26 to 29)

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Organization: Public Health Agency of Canada

Date published: 2019-07-26

Related Topics

Overall Summary

  • Influenza activity is at interseasonal levels across the country.
  • The majority of regions in Canada are reporting no influenza activity.
  • Influenza A is the most common influenza virus circulating in Canada.
  • The next FluWatch report will be published on August 30, 2019. Weekly reporting of laboratory detections of respiratory viruses continues via our Respiratory Virus Detections Surveillance System.

Influenza/Influenza-like Illness Activity (geographic spread)

During week 29, the following influenza activity levels were reported (Figure 1):

  • One region in Alta. reported localized activity
  • 13 regions reported sporadic activity: B.C.(3), Alta.(2), Ont.(5), Que.(2), and P.E.I. (1)
  • 38 regions in 12 provinces and territories reported no activity.

Figure 1 – Map of overall influenza/ILI activity by province and territory, Canada, week 2019-29

Figure 1. Text equivalent follows.
Figure 1 - Text equivalent
Province Influenza Surveillance Region Activity Level
N.L. Eastern No Activity
N.L. Labrador-Grenfell No Activity
N.L. Central No Activity
N.L. Western No Activity
P.E.I. Prince Edward Island Sporadic
N.S. Zone 1 - Western No Activity
N.S. Zone 2 - Northern No Activity
N.S. Zone 3 - Eastern No Activity
N.S. Zone 4 - Central No Activity
N.B. Region 1 No Activity
N.B. Region 2 No Activity
N.B. Region 3 No Activity
N.B. Region 4 No Activity
N.B. Region 5 No Activity
N.B. Region 6 No Activity
N.B. Region 7 No Activity
Que. Nord-est No Activity
Que. Québec et Chaudieres-Appalaches No Activity
Que. Centre-du-Québec Sporadic
Que. Montréal et Laval Sporadic
Que. Ouest-du-Québec No Activity
Que. Montérégie No Activity
Ont. Central East Sporadic
Ont. Central West Sporadic
Ont. Eastern Sporadic
Ont. North East No Activity
Ont. North West No Data
Ont. South West Sporadic
Ont. Toronto Sporadic
Man. Northern Regional No Activity
Man. Prairie Mountain No Activity
Man. Interlake-Eastern No Activity
Man. Winnipeg No Activity
Man. Southern Health No Activity
Sask. North No Activity
Sask. Central No Activity
Sask. South No Activity
Alta. North Zone Sporadic
Alta. Edmonton Sporadic
Alta. Central Zone No Activity
Alta. Calgary Localized
Alta. South Zone No Activity
B.C. Interior No Activity
B.C. Fraser Sporadic
B.C. Vancouver Coastal Sporadic
B.C. Vancouver Island Sporadic
B.C. Northern No Activity
Y.T. Yukon No Activity
N.W.T. North No Activity
N.W.T. South No Activity
Nvt. Qikiqtaaluk No Activity
Nvt. Kivalliq No Activity
Nvt. Kitimeot No Activity

Laboratory-Confirmed Influenza Detections

During weeks 26-29, the following results were reported from sentinel laboratories across Canada (Figures 2 and 3):

  • The percentage of tests positive for influenza continued to decrease from 3.1% in week 26 to 1.6% in week 29.
  • A total of 181 laboratory detections of influenza were reported during these four weeks, of which 71% were influenza A. Influenza A(H3N2) accounted for 93% of subtyped influenza A detections during these five weeks.

To date this season, 48,694 laboratory-confirmed influenza detections have been reported:

  • 95% have been influenza A. Overall, among the 16,528 influenza A viruses subtyped this season, 69% have been A(H1N1)pdm09.
  • In the earlier part of the season (weeks 43-7) influenza A(H1N1)pdm09 was the predominant circulating subtype, followed by a smaller late-season wave of influenza A(H3N2) (weeks 8-21).
  • Fewer influenza B detections have been reported this season compared to recent seasons.

To date this season, detailed information on age and type/subtype has been received for 39,111 laboratory-confirmed influenza cases (Table 1):

  • 83% of all influenza A(H1N1)pdm09 detections have been reported in individuals younger than 65 years of age.
  • 58% of all influenza A(H3N2) detections have been reported in adults 65 years of age and older.

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 – Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, weeks 2018-35 to 2019-29

Figure 2. Text equivalent follows.

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.

Data for week 14 excludes subtyping results from one jurisdiction due to batch reporting of subtype information. The results for week 14 should be interpreted with caution.

Figure 2 - Text equivalent
Surveillance Week A(Unsubtyped) A(H3N2) A(H1N1)pdm09 Influenza B
35 3 2 7 0
36 4 7 4 0
37 3 2 3 1
38 6 3 2 3
39 11 5 1 3
40 16 7 29 3
41 27 6 21 3
42 40 19 55 2
43 83 23 128 4
44 169 13 214 6
45 244 18 295 15
46 346 10 404 9
47 449 17 507 8
48 679 29 632 10
49 851 35 785 16
50 1368 35 828 14
51 1890 54 953 21
52 2292 55 903 26
1 2387 58 893 31
2 1985 93 1061 43
3 1613 101 585 40
4 1483 93 532 48
5 1449 112 433 43
6 1234 118 315 42
7 1116 128 244 33
8 1066 236 216 40
9 1172 285 213 64
10 1085 335 268 71
11 990 357 197 90
12 959 380 155 131
13 939 387 128 167
14 1091 292 41 169
15 756 514 121 157
16 614 277 42 175
17 448 244 55 194
18 265 160 29 148
19 266 154 33 151
20 137 163 27 136
21 89 79 8 122
22 43 53 17 75
23 33 42 8 60
24 39 44 5 48
25 29 41 4 31
26 23 30 0 27
27 15 23 3 12
28 10 18 2 11
29 9 16 1 9

Figure 3 – Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, weeks 2018-35 to 2019-29

Figure 3. Text equivalent follows.
Figure 3 - Text equivalent
Reporting provincesTable Figure 3 - Footnote 1 Week (June 23 to July 20, 2019) Cumulative (August 26, 2018 to July 20, 2019)
Influenza A B Influenza A B A & B
Total
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
BC 67 3 49 15 5 6429 3162 1646 1621 242 6671
AB 30 0 27 3 8 7249 3642 1384 2223 365 7614
SK 0 0 0 0 0 2457 1389 142 926 109 2566
MB 0 0 0 0 3 1193 335 131 727 77 1270
ON 12 2 7 3 10 6400 2106 1729 2565 307 6707
QC 12 0 0 12 17 17161 0 0 17161 978 18139
NB 0 0 0 0 1 2883 246 39 2598 366 3249
NS 0 0 0 0 0 786 0 0 786 22 808
PEI 1 0 0 1 0 279 221 56 2 2 281
NL 0 0 0 0 8 1035 1 0 1034 13 1048
YT 6 1 4 1 0 137 66 32 39 0 137
N.W.T 0 0 0 0 1 181 175 6 0 3 184
NU 0 0 0 0 0 20 20 0 0 0 20
Canada 128 6 87 35 53 46210 11363 5165 29682 2484 48694
PercentageTable Figure 3 - Footnote 2 71% 5% 68% 27% 29% 95% 25% 11% 64% 5% 100%
Table Figure 3 - Footnote 1

Specimens from NWT, YT, and Nvt 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.

Table 1 – Cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reporting, Canada, weeks 2018-35 to 2019-25
Age groups (years) Cumulative (August 26, 2018 to July 20, 2019)
Influenza A B Influenza A and B
A Total A(H1N1) pdm09 A(H3N2) A (UnS)Table 1 – Note 1 Total # %
0-4 6790 1694 275 4821 376 7166 18%
5-19 5196 1393 505 3298 631 5827 15%
20-44 6973 2028 655 4290 428 7401 19%
45-64 7118 1985 716 4417 142 7260 19%
65+ 11183 1494 2924 6765 274 11457 29%
Total 37260 8594 5075 23591 1851 39111 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 29, 0.3% of visits to healthcare professionals were due to influenza-like illness (ILI) (Figure 4).

Figure 4 – Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2018-35 to 2019-29

Number of Sentinels Reporting in Week 29: 77

Figure 4. Text equivalent follows.

The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2013-2014 to 2017-2018

Figure 4 - Text equivalent
Surveillance Week 2018-19 Average Min Max
35 0.6% 0.8% 0.5% 1.2%
36 0.7% 0.8% 0.7% 1.0%
37 0.6% 0.9% 0.7% 1.0%
38 0.5% 1.1% 1.0% 1.4%
39 1.7% 1.1% 0.9% 1.4%
40 0.6% 1.3% 0.9% 1.6%
41 1.1% 1.4% 0.9% 2.4%
42 1.1% 1.4% 1.0% 1.9%
43 1.0% 1.3% 1.0% 1.5%
44 0.8% 1.3% 0.9% 1.6%
45 1.3% 1.3% 1.2% 1.5%
46 1.3% 1.6% 1.0% 2.0%
47 1.3% 1.5% 1.1% 1.9%
48 1.5% 1.6% 0.8% 2.1%
49 1.6% 1.5% 1.0% 2.5%
50 1.5% 2.3% 1.3% 3.7%
51 1.1% 2.5% 1.6% 4.1%
52 3.2% 4.5% 1.7% 7.1%
1 2.8% 3.7% 1.7% 5.2%
2 1.8% 3.0% 1.1% 4.5%
3 1.1% 2.5% 1.3% 3.6%
4 1.4% 2.4% 1.7% 3.5%
5 1.4% 2.7% 2.0% 4.4%
6 0.9% 2.7% 2.1% 3.3%
7 0.9% 2.4% 1.7% 3.0%
8 1.0% 2.3% 1.9% 2.7%
9 1.1% 2.2% 1.8% 2.7%
10 1.1% 2.1% 1.8% 2.7%
11 0.6% 2.1% 1.7% 2.7%
12 1.1% 1.8% 1.1% 2.7%
13 1.1% 1.7% 1.2% 2.6%
14 1.0% 1.8% 1.3% 2.4%
15 0.8% 1.6% 0.9% 1.9%
16 0.7% 1.5% 1.0% 1.9%
17 0.5% 1.5% 0.9% 2.2%
18 0.7% 1.2% 0.8% 1.6%
19 0.8% 1.3% 1.0% 1.7%
20 0.8% 1.2% 0.9% 1.4%
21 0.9% 0.9% 0.3% 1.3%
22 0.9% 0.8% 0.6% 1.0%
23 0.9% 0.9% 0.6% 1.2%
24 0.9% 0.7% 0.4% 1.0%
25 0.8% 1.2% 0.5% 1.6%
26 0.5% 0.8% 0.4% 1.4%
27 0.5% 0.8% 0.4% 1.5%
28 1.0% 1.0% 0.6% 1.9%
29 0.3% 0.8% 0.5% 1.1%

Participatory Syndromic Surveillance

FluWatchers surveillance has ended for the 2018-19 influenza season. On average 2,097 participants reported to FluWatchers each week, resulting in 64,672 questionnaires completed this season. The proportion of participants reporting fever and cough peaked in week 51 at 3.9% (Figure 5). Approximately 63% of FluWatchers participants reported being vaccinated for influenza in the 2018-19 season.

Figure 5 - Percentage of participants reporting cough and fever, Canada, weeks 2018-40 to 2019-18

Number of Participants Reporting in Week 18: 1,951

Figure 5. Text equivalent follows.
Figure 5 - Text equivalent
Surveillance Week % cough and fever
40 2.6%
41 2.5%
42 1.7%
43 1.5%
44 1.3%
45 1.7%
46 2.0%
47 1.3%
48 2.4%
49 2.0%
50 3.7%
51 3.9%
52 3.6%
1 3.4%
2 2.8%
3 2.5%
4 2.9%
5 3.0%
6 2.6%
7 2.7%
8 2.5%
9 2.7%
10 3.1%
11 2.6%
12 2.4%
13 2.4%
14 2.3%
15 1.8%
16 2.4%
17 2.3%
18 1.9%

Influenza Outbreak Surveillance

In weeks 26 to 29, two new laboratory-confirmed influenza outbreaks were reported: one in a long-term care facility (LTCF) (1) and one in an acute care facility(1). Both outbreaks were associated with influenza A.

To date this season, 931 laboratory-confirmed influenza outbreaks have been reported (Figure 6):

  • 545 (59%) outbreaks were in LTCF, 32 were in schools and daycares, 130 in acute care facilities, and 224 were in other settings.
  • Among the 844 outbreaks for which the influenza type was available, 98% (824) were associated with influenza A.
  • Among the 387 outbreaks for which the influenza A subtype was available, 65% (253) were associated with influenza A(H3N2);

To date this season, 176 ILI outbreaks have been reported; 108 occurred in LTCF, 62 in schools, five in acute care facilities, and one in other settings.

Figure 6 – Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2018-35 to 2019-29

Figure 6. Text equivalent follows.
Figure 6 - Text equivalent
Surveillance Week Acute Care Facilities Long Term Care Facilities Other Schools and Daycares Remote and/or Isolated Communities
35 0 0 0 0 0
36 0 0 0 0 0
37 0 0 0 0 0
38 0 0 0 0 0
39 0 0 0 0 0
40 0 2 0 1 0
41 0 0 0 0 0
42 0 2 1 0 0
43 0 3 1 0 0
44 0 1 1 2 0
45 0 2 1 3 0
46 2 5 1 3 0
47 2 4 0 1 0
48 2 6 1 5 0
49 1 2 3 1 0
50 3 9 5 4 0
51 3 12 4 2 0
52 4 25 5 0 0
1 5 40 11 0 0
2 8 38 7 0 0
3 3 27 10 0 0
4 6 19 10 1 0
5 6 24 6 0 0
6 9 23 7 0 0
7 6 20 8 0 0
8 5 31 11 4 0
9 9 23 15 2 0
10 12 28 8 1 0
11 5 26 15 0 0
12 9 23 14 0 0
13 9 24 11 0 0
14 6 26 8 0 0
15 7 26 12 1 0
16 0 18 13 0 0
17 1 15 13 0 0
18 2 17 5 0 0
19 1 11 2 0 0
20 1 2 4 1 0
21 0 5 4 0 0
22 1 0 1 0 0
23 1 3 3 0 0
24 0 2 1 0 0
25 0 0 2 0 0
26 0 1 0 0 0
27 0 0 0 0 0
28 0 0 0 0 0
29 1 0 0 0 0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 3,634 influenza-associated hospitalizations have been reported by participating provinces and territoriesFootnote 1.

Hospitalizations (Table 2):

  • 96% (3,503) were associated with influenza A
  • Among the 2,135 cases for which the influenza subtype was available, 1,453 (68%) were associated with A(H1N1)pdm09.
  • The highest estimated rate of hospitalization is among adults over 65 years of age.

Intensive Care Unit (ICU) cases and deaths:

  • To date this season 613 ICU admissions and 221 deaths have been reported.
    • 38% (241) of reported ICU admissions were in adults aged 45-64 years.
    • 97% (595) of ICU admissions were associated with influenza A.
    • All but four of the deaths were associated with influenza A.
Table 2 – Cumulative number and estimated rate of hospitalizations by age-group reported by participating provinces and territoriesFootnote 1, Canada, weeks 2018-35 to 2019-29
Age Groups (years) Cumulative (August 26, 2018 to July 20, 2019)
Influenza A Influenza B Rate per 100,000 population
0-4 422 39 96.85
5-19 266 34 21.62
20-44 386 20 14.27
45-64 857 15 40.07
65+ 1572 23 131.10
Total 3503 131  
% 96.4% 3.6%  
Table 2 Footnote 1

Influenza-associated hospitalizations are reported by N.L., P.E.I, N.S., N.B., Man., Alb., Y.T. and N.W.T. Only hospitalizations that require intensive medical care are reported by Sask. The cumulative rate of hospitalizations is calculated using the population by age-group in participating provinces and territories.

Table 2 footnote 1 referrer

Pediatric Influenza Hospitalizations and Deaths

To date this season, 1,340 pediatric hospitalizations have been reported (Figure 7 & 8):

  • 66% of cases were in children under 5 years of age.
  • 91% (1,217) of cases have been associated with influenza A.
  • Among the 384 cases for which the influenza subtype was available, 307 (80%) were associated with A(H1N1)pdm09.

To date this season, 265 ICU admissions, and 10 deaths have been reported.

  • 60% (158) of ICU admissions were in children under 5 years of age.
  • 92% (244) of ICU admissions have been associated with influenza A; 81% of the 108 cases for which the influenza A subtype was available were associated with A(H1N1)pdm09.
  • 80% (8) of deaths occurred in children 2 to 4 years of age.
  • All deaths have been associated with influenza A.

Figure 7 – Number of pediatric (≤16 years of age) hospitalizations reported by the IMPACT network, by week, Canada, weeks 2018-35 to 2019-29

Figure 7. Text equivalent follows.

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2017-19

Figure 7 - Text equivalent
Surveillance week 2018-19 Average Min Max
35 0 0 0 0
36 0 0 0 1
37 0 0 0 2
38 0 0 0 2
39 0 1 0 3
40 0 0 0 2
41 1 1 0 2
42 5 1 0 4
43 12 1 0 3
44 15 3 1 6
45 37 3 2 4
46 41 5 1 13
47 37 4 0 9
48 40 9 2 23
49 47 15 3 28
50 51 23 4 47
51 84 32 4 72
52 89 47 7 92
1 91 40 5 75
2 63 35 4 62
3 64 38 4 67
4 67 35 7 47
5 50 40 11 59
6 45 38 15 79
7 45 40 17 120
8 44 47 25 139
9 33 50 13 153
10 45 48 17 135
11 43 41 18 118
12 41 33 13 89
13 28 32 14 67
14 31 24 12 56
15 28 23 13 56
16 33 20 10 41
17 33 16 8 37
18 22 14 4 28
19 19 10 5 18
20 17 10 4 19
21 10 5 2 10
22 8 4 1 8
23 6 2 0 5
24 7 2 0 5
25 5 1 0 3
26 2 1 0 3
27 1 1 0 2
28 0 1 0 2
29 0 0 0 2

Figure 8 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by age-group reported by the IMPACT network, Canada, weeks 2018-35 to 2019-29

Figure 8. Text equivalent follows.
Figure 8 - Text equivalent
Age Group Total
0-5 mo 143
6-23 mo 329
2-4 yr 413
5-9 yr 301
10-16 yr 154

Adult Influenza Hospitalizations and Deaths

Surveillance of laboratory-confirmed influenza-associated adult (≥16 years of age) hospitalizations by the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) network began on November 1st and ended  May 30th for the 2018-19 season.

This season, 950 hospitalizations, 127 ICU admissions and 57 deaths have been reported (Figure 9):

  • 876 (92%) hospitalizations were associated with influenza A.
  • A greater proportion of hospitalizations have been reported among  adults ≥65 years of age (60%) compared to adults <65 years of age (40%).
  • Among the 208 cases for which the influenza subtype was available, 107 (51%) were associated with A(H1N1)pdm09.
  • 88% of hospitalized cases reported more than one type of comorbid condition.  
  • The most commonly reported comorbidity was endocrine disorders, which were reported in 88% of hospitalized cases.

Figure 9 - Cumulative numbers of adult hospitalizations (>20 years of age) with influenza by age-group reported by CIRN, Canada, 2018-19, weeks 2018-44 to 2019-25

Figure 9. Text equivalent follows.
Figure 9 - Text equivalent
Age Group Total
20-34 yr 93
35-49 yr 85
50-64 yr 199
65-79 yr 273
80+ yr 300

Influenza Strain Characterizations

From September 1, 2018 to July 20, 2019, the National Microbiology Laboratory (NML) has characterized 2,526 influenza viruses (639 A(H3N2), 1,652 A(H1N1) and 235 B) that were received from Canadian laboratories.

Genetic Characterization of Influenza A(H3N2):

270 influenza A(H3N2) viruses did not grow to sufficient hemagglutination titer for antigenic characterization by hemagglutination inhibition (HI) assay. Therefore, NML has performed genetic characterization to determine the genetic group identity of these viruses.

Sequence analysis of the HA gene of the viruses showed that:

  • 20 viruses belonged to genetic group 3C.2a.
  • 241 viruses belonged to subclade 3C.2a1.
  • Eight viruses belonged to 3C.3a.
  • One isolate could not be sequenced.

A/Singapore/INFIMH-16-0019/2016-like virus belongs to genetic group 3C.2a1 and is the influenza A(H3N2) component of the 2018-19 Northern Hemisphere influenza vaccine.

Antigenic Characterization:

Influenza A (H3N2):

  • 207 influenza A(H3N2) viruses were antigenically characterized as A/Singapore/INFIMH-16-0019/2016-like by HI testing using antiserum raised against egg-propagated A/Singapore/INFIMH-16-0019/2016.
  • 162 viruses showed reduced titer with ferret antisera raised against egg-propagated A/Singapore/INFIMH-16-0019/2016.
  • A/Singapore/INFIMH-16-0019/2016-like virus is the influenza A(H3N2) component of the 2018-19 Northern Hemisphere influenza vaccine.
  • 200 influenza A(H3N2) viruses characterized belonged to genetic group 3C.3a, 140 viruses to 3C.2a1. and 20 viruses belonged to genetic group 3C.2a . Sequencing is pending for the remaining isolates.

Influenza A(H1N1):

  • 1,608 A(H1N1) viruses characterized were antigenically similar to A/Michigan/45/2015, which is the influenza A(H1N1) component of the 2018-19 Northern Hemisphere influenza vaccine.
  • 44 viruses showed reduced titer with ferret antisera raised against cell culture-propagated A/Michigan/45/2015

Influenza B:

Influenza B viruses can be divided into two antigenically distinct lineages represented by B/Yamagata/16/88 and B/Victoria/2/87 viruses. The recommended influenza B components for the 2018-19 Northern Hemisphere influenza vaccine are B/Colorado/06/2017 (Victoria lineage) and B/Phuket/3073/2013 (Yamagata lineage).

  • 45 influenza B viruses were characterized as B/Colorado/06/2017, which belong to the Victoria lineage and are included as an influenza B component of the 2018-19 Northern Hemisphere influenza vaccine.
  • 164 viruses showed reduced titer with ferret antisera raised against cell culture-propagated B/Colorado/06/2017. Sequence analysis showed that 158 viruses that showed reduced titer had a three amino acid deletion (162-164) in the HA gene.
  • 26 influenza B viruses were characterized as B/Phuket/3073/2013-like, which belongs to the Yamagata lineage and is included as an influenza B component of the 2018-19 Northern Hemisphere quadrivalent influenza vaccine.

Antiviral Resistance

Antiviral Resistance – Amantadine:

519 influenza A (121 A(H3N2) and 380 A(H1N1)) viruses were tested for resistance to amantadine and it was found that:

  • All 519 influenza A viruses were resistant to amantadine.

Antiviral Resistance – Oseltamivir:

1,431 influenza viruses (214 A(H3N2), 1,080 A(H1N1) and 137 B) were tested for resistance to oseltamivir and it was found that:

  • All 214 A(H3N2) viruses were sensitive to oseltamivir.
  • Of the 1,080 A(H1N1) viruses tested, 1,076 were sensitive to oseltamivir and four viruses were resistant to oseltamivir with a H275Y mutation.
  • All 137 B viruses were sensitive to oseltamivir.

Antiviral Resistance – Zanamivir:

1,429 influenza viruses (214 A(H3N2), 1,078 H1N1 and 137 B) were tested for resistance to zanamivir and it was found that:

  • All 1,429 influenza viruses were sensitive to zanamivir.

Vaccine Monitoring

Vaccine monitoring refers to activities related to the monitoring of influenza vaccine coverage and effectiveness.

Vaccine Coverage

The Seasonal Influenza Immunization Coverage Survey is an annual telephone survey conducted between January and February that collects information related to the influenza vaccine in Canada. This survey measures vaccine coverage, which is the percentage of people who received the annual seasonal influenza vaccine in a specific influenza season.

In the 2018-19 influenza season, coverage was:

  • 34% among adults aged 18 to 64 years.
    • 31% among adults aged 18-64 wihout chronic diseases.
    • 43% among adults aged 18 to 64 years with chronic diseases.
  • 70% among seniors (aged 65 years and older).
Table 3 – Influenza vaccine coverage among adults (≥ 18 years of age) by age group, gender and chronic diseaseTable 3 – Note 1, Seasonal Influenza Vaccination Coverage Survey, Canada, October 2018-February 2019
Age group (years) Male Female Combined
Total Vaccine Coverage (%) Total Vaccine Coverage (%) Total Vaccine Coverage (%)
All adults (≥18) 1568 36.6 2150 46.8 3726 41.8
18-64 1252 28.6 1640 39.9 2898 34.3
without chronic diseases 948 25.8 1171 36.1 2124 30.8
with chronic diseases 304 36.3 465 48.5 770 42.8
≥65 316 69.0 510 70.9 828 69.9
Table 3 Footnote 1

Excluded from stratified analysis: eight people who did not disclose their gender and four people (18-64 years old) who did disclose whether they had any chronic diseases.

Table 3 footnote 1 referrer

Vaccine Effectiveness

Vaccine effectiveness (VE) is a measure of how well the influenza vaccine is able to prevent influenza illness. Throughout the influenza season, surveillance networks estimate how well the influenza vaccine is working. Estimates can vary depending on several factors such as the study methods; the population, setting and outcomes that are being studied; the type and mix of vaccine products; the stage of the season and the kinds of influenza viruses that are circulating when the study is conducted.

The community-based Canadian Sentinel Practitioner Surveillance Network (SPSN) published an interim VE estimate in January 2019 for A(H1N1)pdm09. Subsequently, given an atypical late-season wave of influenza A(H3N2),SPSN has undertaken an additional interim analysis to assess effectiveness of the 2018/19 influenza vaccine against medically-attended outpatient A(H3N2) illness. Vaccine effectiveness (VE) monitoring methods and results are available at the SPSN website.

Based on data collected as of March 30th, 2019 from more than 2800 patients from B.C., Alta., Ont., and Que., the 2018/19 northern hemisphere vaccine effectiveness has varied depending on the strain.

  • A(H1N1)pdm09: In the first interim analysis, VE against A(H1N1)pdm09 was 72% (95% CI: 60 to 81) overall, with substantial protection observed in all age groups. In the most recent analysis as of March 30th, estimates against A(H1N1)pmd09 have remained stable at approximately 70%.
  • A(H3N2): In the most recent analysis, VE against A(H3N2) was 23% (95% CI: -9 to 46) overall. As the confidence interval crosses zero, this estimate does not provide evidence of vaccine protection against medically-attended outpatient A(H3N2) illness.

The SPSN continues to monitor and will further update VE estimates at end of season.

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