FluWatch report: April 16 to April 29, 2023 (weeks 16-17)

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Organization: Public Health Agency of Canada

Published: 2023-05-05

Weekly Highlights

  • At the national level, influenza activity has been stable and remains at interseasonal levels. Sporadic influenza activity continues to be reported in many regions across Canada.

Virologic

  • In week 17, the percentage of tests positive for influenza was 2.2% and a total of 448 laboratory detections (362 influenza B and 86 influenza A) were reported. Influenza B detections (81%) are predominant.

Syndromic

  • The percentage of visits for influenza-like illness (ILI) was 1.0% in week 17. The percentage of visits for ILI is within levels typical of this time of year.
  • The percentage of FluWatchers reporting fever and cough was 1.2% in week 17, below levels typical of this time of year.

Outbreaks

  • From August 28, 2022 to April 29, 2023 (weeks 35 to 17), 658 laboratory-confirmed influenza outbreaks have been reported (one laboratory-confirmed influenza outbreak was reported in week 17).

Severe Outcomes

  • In recent weeks, there has been an increase in the number of weekly hospitalizations due to influenza B.
  • The highest cumulative hospitalization rate up to week 17 is among adults 65 years of age and older (133/100,000 population) and children under 5 years of age (126/100,000 population). The overall cumulative hospitalization rate this season to date is 48/100,000 population.

Other Notes

On this page

Influenza/Influenza-like Illness Activity - Geographic Spread

In week 17, 31 regions across Canada reported either sporadic or localized influenza activity (Figure 1). The number of regions reporting influenza activity and the intensity of reported activity remains stable. A total of 18 regions in Canada reported no activity this week.

Figure 1 - Map of influenza/ILI activity by province and territory, Canada, week 2023-17

Number of Regions Reporting in Week 17: 49 out of 53

Figure 1. Text version below
Figure 1 - Text description
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 No Data
N.S. Zone 1 - Western No Activity
N.S. Zone 2 - Northern No Activity
N.S. Zone 3 - Eastern Sporadic
N.S. Zone 4 - Central Sporadic
N.B. Region 1 No Activity
N.B. Region 2 No Activity
N.B. Region 3 Localized
N.B. Region 4 Sporadic
N.B. Region 5 No Activity
N.B. Region 6 No Activity
N.B. Region 7 No Activity
Que. Nord-est Sporadic
Que. Québec et Chaudieres-Appalaches Sporadic
Que. Centre-du-Québec Sporadic
Que. Montréal et Laval Sporadic
Que. Ouest-du-Québec Sporadic
Que. Montérégie Sporadic
Ont. Central East Localized
Ont. Central West Sporadic
Ont. Eastern Localized
Ont. North East Sporadic
Ont. North West No Activity
Ont. South West Sporadic
Ont. Toronto Sporadic
Man. Northern Regional Sporadic
Man. Prairie Mountain Sporadic
Man. Interlake-Eastern No Activity
Man. Winnipeg Sporadic
Man. Southern Health No Activity
Sask. North No Data
Sask. Central No Data
Sask. South No Data
Alta. North Zone Sporadic
Alta. Edmonton Sporadic
Alta. Central Zone Sporadic
Alta. Calgary Sporadic
Alta. South Zone Sporadic
B.C. Interior Sporadic
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 Sporadic
Nvt. Kivalliq Sporadic
Nvt. Kitimeot Sporadic

Laboratory-Confirmed Influenza Detections

The weekly percentage of tests positive for influenza (2.2% in week 17) remains stable and is at interseasonal levels. Taking into consideration historical trends and with current influenza A and B activity at low, stable levels, the end of the influenza season at the national level occurred in week 1 (week ending January 7, 2023) when the percentage of tests crossed below the seasonal threshold of 5%.

The following results were reported from sentinel laboratories across Canada in week 17 (Figures 2 and 3):

To date this season (August 28, 2022 to April 29, 2023):

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, week 2022-35 to 2023-17

Number of Laboratories Reporting in Week 17: 33 out of 35

Figure 2. Text version below
Figure 2 - Text description
Surveillance Week A(Unsubtyped) A(H3N2) A(H1N1) Influenza B Percent Positive A Percent Positive B
35 13 10 2 3 0.2 0.0
36 9 5 1 5 0.1 0.0
37 19 9 3 2 0.2 0.0
38 26 35 20 3 0.5 0.0
39 44 53 22 5 0.7 0.0
40 64 66 16 4 1.0 0.0
41 121 110 20 1 1.4 0.0
42 218 204 11 9 2.4 0.1
43 418 595 23 6 5.5 0.0
44 1055 1351 54 7 10.9 0.0
45 2026 2268 69 11 16.2 0.0
46 3453 2983 98 16 20.2 0.1
47 5916 2912 168 16 24.1 0.0
48 7372 2605 133 13 23.8 0.0
49 7028 2206 141 29 21.0 0.1
50 5686 1507 137 29 17.2 0.1
51 3776 849 155 19 12.5 0.1
52 2272 506 105 28 8.0 0.1
1 1338 316 86 29 4.6 0.1
2 553 139 54 18 2.2 0.1
3 326 47 49 44 1.4 0.1
4 172 40 42 42 0.9 0.2
5 154 25 35 80 0.8 0.3
6 138 18 30 94 0.7 0.3
7 98 11 31 75 0.6 0.3
8 102 20 20 127 0.6 0.5
9 109 18 30 182 0.6 0.7
10 109 10 26 201 0.6 0.8
11 89 7 25 296 0.5 1.2
12 104 3 29 311 0.6 1.3
13 124 11 21 424 0.6 1.7
14 63 1 20 425 0.4 1.9
15 118 2 17 455 0.6 1.9
16 97 5 12 410 0.5 1.8
17 64 2 20 362 0.4 1.8
Figure 3 - Percentage of tests positive in Canada compared to previous seasons, week 2022-35 to 2023-17
Figure 3. Text version below.

The shaded area represents the maximum and minimum number of influenza tests or percentage of tests positive reported by week from seasons 2014-2015 to 2019-2020. Data from week 15 of the 2019-2020 season onwards are excluded from the historical comparison due to the COVID-19 pandemic.

The epidemic threshold is 5% tests positive for influenza. When it is exceeded, and a minimum of 15 weekly influenza detections are reported, a seasonal influenza epidemic is declared.

Figure 3 - Text description
Surveillance Week Percentage of tests positive, 2022-2023 Percentage of tests positive, 2021-2022 Percentage of tests positive, 2020-2021 Maximum Percentage of Tests Positive Minimum Percentage of Tests Positive Average Percentage of Tests Positive
35 0.2 0.0 0.0 1.9 0.1 0.8
36 0.2 0.0 0.0 2.3 0.3 1.1
37 0.3 0.0 0.0 1.8 0.4 1.0
38 0.5 0.0 0.0 2.4 0.5 1.3
39 0.7 0.0 0.0 2.9 0.7 1.7
40 1.0 0.0 0.0 2.3 1.1 1.7
41 1.5 0.1 0.0 3.0 1.3 1.7
42 2.4 0.1 0.0 3.4 0.9 2.2
43 5.6 0.1 0.0 5.3 0.8 2.8
44 10.9 0.2 0.1 8.5 1.2 3.7
45 16.2 0.1 0.0 10.1 1.4 4.6
46 20.2 0.2 0.0 14.1 1.5 6.1
47 24.1 0.2 0.1 15.4 1.4 7.7
48 23.9 0.3 0.1 18.2 0.8 10.6
49 21.0 0.3 0.0 19.7 1.6 13.0
50 17.3 0.3 0.0 27.0 2.4 16.8
51 12.5 0.2 0.0 29.1 3.3 20.1
52 8.0 0.1 0.0 34.5 4.3 24.5
1 4.7 0.1 0.0 31.7 5.8 23.4
2 2.3 0.1 0.0 29.1 7.1 23.0
3 1.5 0.1 0.0 30.1 12.2 23.6
4 1.1 0.1 0.0 29.5 15.9 24.0
5 1.0 0.0 0.0 30.6 19.6 24.9
6 1.0 0.1 0.0 32.4 17.9 25.0
7 0.8 0.0 0.0 32.5 16.3 25.1
8 1.1 0.1 0.0 32.9 17.5 25.1
9 1.3 0.1 0.0 34.3 16.8 24.6
10 1.4 0.2 0.0 36.0 16.0 23.2
11 1.7 0.3 0.0 31.4 16.2 21.4
12 1.9 0.9 0.0 30.0 15.0 20.1
13 2.4 1.5 0.0 28.3 14.5 19.6
14 2.2 2.5 0.0 23.2 12.7 17.9
15 2.5 3.9 0.0 20.7 11.9 16.3
16 2.3 7.0 0.0 18.5 11.6 14.5
17 2.2 9.7 0.0 17.3 9.8 12.8
18 N/A 11.3 0.0 13.0 7.9 10.3
19 N/A 12.6 0.0 11.9 5.0 9.0
20 N/A 10.4 0.0 9.1 3.2 7.2
21 N/A 9.8 0.0 7.4 3.0 5.6
22 N/A 8.4 0.0 5.0 2.2 3.9
23 N/A 7.0 0.0 4.4 0.9 2.9
24 N/A 5.0 0.0 4.4 0.8 2.2
25 N/A 3.0 0.0 3.9 0.6 1.9
26 N/A 2.3 0.0 3.1 0.7 1.8
27 N/A 1.2 0.0 2.8 0.4 1.5
28 N/A 0.8 0.0 1.8 0.4 0.9
29 N/A 0.7 0.0 1.6 0.5 1.1
30 N/A 0.4 0.0 1.5 0.5 0.9
31 N/A 0.3 0.0 1.9 0.6 1.1
32 N/A 0.2 0.0 1.2 0.5 0.9
33 N/A 0.2 0.0 1.7 0.4 0.9
34 N/A 0.2 0.0 1.6 0.4 0.9

Figure 4 - Proportion of positive influenza specimens by type or subtype and age-group reported through case-based laboratory reporting, Canada, week 2022-35 to 2023-17

Figure 4. Text version below.

Laboratory data notes:

Testing for influenza and other respiratory viruses has been influenced by the current COVID-19 pandemic. Changes in laboratory testing practices may affect the comparability of data to previous seasons.

Due to different testing protocols of laboratories across Canada, some influenza A subtype detection counts may not be included in total influenza A detection counts and percent positivity calculations.

Figure 4 - Text description
a) Proportion of influenza A and B by age-group
Age Group Proportion of Influenza A Proportion of Influenza B Total Number Influenza Detections
0 to 4 93.8% 6.2% 9063
5 to 19 92.8% 7.2% 11674
20 to 44 91.0% 9.0% 10637
45 to 64 96.4% 3.6% 6617
65+ 98.9% 1.1% 12824
b) Proportion of subtyped influenza A(H1N1) and A(H3N2) by age-group
Age Group Proportion of A(H1N1) Proportion of A(H3N2) Total Number of Subtyped Influenza Detections
0 to 4 5.6% 94.4% 2847
5 to 19 4.7% 95.3% 3576
20 to 44 9.4% 90.6% 2894
45 to 64 17.2% 82.8% 1870
65+ 9.7% 90.3% 3627

Syndromic / Influenza-like Illness Surveillance

Healthcare Practitioners Sentinel Surveillance

In week 17, 1.0% of visits to healthcare professionals were due to influenza-like illness (ILI) (Figure 5). The percentage of visits for ILI is within expected levels for this time of year.

ILI symptoms are not specific to any one respiratory pathogen and can be due to influenza, or other respiratory viruses, including respiratory syncytial virus and SARS-CoV-2, the virus that causes COVID-19. This makes the percentage of visits for ILI an important indicator of overall respiratory illness morbidity in the community in the presence of co-circulating viruses.

This indicator should be interpreted with caution as there have been changes in healthcare seeking behavior of individuals and a smaller number of sentinels reporting compared to previous seasons.

Figure 5 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2022-35 to 2023-17

Number of Sentinels Reporting in Week 17: 39

Figure 5. Text version below.

The shaded area represents the maximum and minimum percentage of percentage of participants reporting cough and fever by week, from seasons 2014-2015 to 2019-2020. Data from week 14-15 of the 2019-2020 season onwards are excluded from the historical comparison due to the COVID-19 pandemic.

Figure 5 - Text description
Surveillance Week 2022-2023 2021-2022 2020-2021 Average Min Max
35 0.6% 0.6% 0.1% 0.6% 0.4% 0.9%
36 0.9% 1.2% 0.2% 0.6% 0.4% 0.9%
37 0.7% 0.6% 0.4% 0.7% 0.5% 1.0%
38 0.8% 0.9% 0.3% 0.7% 0.6% 1.0%
39 1.0% 1.0% 0.4% 0.9% 0.5% 1.2%
40 0.7% 0.5% 0.2% 1.2% 0.8% 1.7%
41 1.9% 1.1% 0.4% 1.7% 0.8% 2.8%
42 1.4% 1.2% 0.5% 1.6% 1.2% 2.1%
43 1.6% 0.9% 0.3% 1.2% 0.8% 1.7%
44 1.5% 0.6% 0.3% 1.2% 0.7% 1.7%
45 2.2% 1.0% 0.4% 1.2% 0.9% 1.5%
46 2.3% 0.9% 0.8% 1.4% 1.2% 1.8%
47 3.5% 0.7% 0.3% 1.6% 1.1% 2.2%
48 3.2% 1.1% 0.5% 1.5% 1.1% 2.2%
49 3.2% 0.9% 0.5% 1.7% 1.0% 2.8%
50 2.4% 1.1% 0.4% 1.5% 1.1% 1.7%
51 1.7% 1.7% 0.5% 1.9% 1.4% 2.7%
52 2.9% 1.5% 0.5% 2.0% 1.0% 3.1%
1 1.6% 2.1% 0.7% 3.4% 1.9% 5.4%
2 1.4% 1.6% 0.4% 3.4% 1.8% 5.7%
3 1.7% 1.4% 0.2% 2.3% 1.3% 3.7%
4 1.0% 0.9% 0.3% 2.0% 1.1% 2.9%
5 1.3% 1.0% 0.2% 2.1% 1.4% 3.1%
6 1.0% 0.7% 0.5% 2.4% 1.4% 4.0%
7 0.7% 0.7% 0.3% 2.4% 0.9% 3.5%
8 0.8% 0.8% 0.2% 2.3% 0.8% 3.4%
9 0.9% 0.7% 0.2% 2.3% 0.9% 3.1%
10 0.7% 0.9% 0.2% 2.0% 1.0% 2.8%
11 0.9% 0.6% 0.2% 1.9% 1.1% 2.8%
12 0.8% 0.8% 0.3% 1.6% 0.6% 2.6%
13 1.1% 1.2% 0.4% 1.6% 1.1% 2.6%
14 0.6% 1.1% 0.2% 1.7% 1.1% 3.0%
15 0.4% 1.2% 0.3% 1.3% 0.9% 1.9%
16 0.9% 1.5% 0.3% 1.2% 0.8% 1.7%
17 1.0% 1.3% 0.4% 1.2% 0.7% 1.7%
18 N/A 1.8% 0.5% 1.3% 0.5% 2.0%
19 N/A 1.7% 0.3% 0.9% 0.6% 1.3%
20 N/A 1.5% 0.5% 1.1% 0.6% 1.5%
21 N/A 1.4% 0.3% 0.9% 0.5% 1.3%
22 N/A 1.0% 0.3% 0.7% 0.3% 1.0%
23 N/A 1.1% 0.2% 0.8% 0.6% 1.0%
24 N/A 1.3% 0.2% 0.7% 0.6% 1.0%
25 N/A 1.0% 0.2% 0.6% 0.4% 0.8%
26 N/A 0.8% 0.2% 0.8% 0.5% 1.4%
27 N/A 1.7% 0.3% 0.6% 0.5% 0.7%
28 N/A 1.0% 0.1% 0.7% 0.5% 1.3%
29 N/A 0.9% 0.3% 0.9% 0.6% 1.7%
30 N/A 1.3% 0.2% 0.6% 0.2% 0.9%
31 N/A 0.9% 0.2% 0.4% 0.2% 0.6%
32 N/A 0.9% 0.2% 0.8% 0.3% 1.2%
33 N/A 0.8% 0.3% 0.7% 0.4% 1.3%
34 N/A 1.0% 0.5% 0.7% 0.4% 1.5%

FluWatchers

In week 17, 9,480 participants reported to FluWatchers, of which 1.2% reported symptoms of cough and fever (Figure 6). The percentage of FluWatchers who have reported cough and fever is below seasonal levels.

The reports of cough and fever are not specific to any one respiratory pathogen and can be due to influenza, or other respiratory viruses, including respiratory syncytial virus, rhinovirus, and SARS-CoV-2, the virus that causes COVID-19. This makes the proportion of individuals reporting cough and fever an important indicator of overall respiratory illness activity in the community in the presence of co-circulating viruses.

FluWatchers reporting is not impacted by changes in health services or health seeking behaviours.

Among the 110 participants who reported cough and fever:

The Northwest Territories had the highest participation rate this week (65 participants per 100,000 population) and the neighbourhood with postal code, K0A had the highest number of participants (131). See what is happening in your neighbourhood! Downloadable datasets are also available on Open Maps.

If you are interested in becoming a FluWatcher, sign up today.

Figure 6 - Percentage of FluWatchers reporting cough and fever, Canada, week 2022-35 to 2023-17

Number of Participants Reporting in Week 17: 9,480

Figure 6. Text version below.

The shaded area represents the maximum and minimum percentage of percentage of participants reporting cough and fever by week, from seasons 2014-2015 to 2019-2020. Data from week 14-15 of the 2019-2020 season onwards are excluded from the historical comparison due to the COVID-19 pandemic.

Figure 6 - Text description
Surveillance Week 2022-2023 2021-2022 2020-2021 Average Min Max
35 1.3% 0.2% 0.2% N/A N/A N/A
36 1.2% 0.3% 0.2% N/A N/A N/A
37 1.6% 0.5% 0.4% N/A N/A N/A
38 1.8% 0.5% 0.3% N/A N/A N/A
39 2.3% 0.5% 0.4% N/A N/A N/A
40 2.4% 0.6% 0.5% 2.5% 2.2% 2.7%
41 2.0% 0.5% 0.4% 2.2% 1.8% 2.6%
42 2.0% 0.4% 0.3% 1.8% 1.6% 2.0%
43 2.3% 0.5% 0.2% 1.9% 1.5% 2.2%
44 2.6% 0.5% 0.3% 1.6% 1.4% 1.8%
45 3.0% 0.5% 0.3% 1.8% 1.4% 2.3%
46 2.9% 0.4% 0.3% 1.8% 1.2% 2.2%
47 3.1% 0.6% 0.3% 1.9% 1.4% 2.4%
48 3.1% 0.5% 0.3% 2.4% 1.7% 3.4%
49 2.7% 0.4% 0.2% 2.6% 2.0% 3.2%
50 2.1% 0.6% 0.1% 2.9% 2.1% 3.8%
51 2.4% 1.0% 0.2% 3.2% 2.5% 3.9%
52 2.1% 1.5% 0.1% 4.0% 2.8% 5.4%
1 1.7% 1.1% 0.1% 3.8% 2.9% 4.8%
2 1.3% 1.0% 0.2% 2.9% 1.9% 3.9%
3 1.3% 0.8% 0.1% 3.3% 2.3% 4.8%
4 1.2% 0.6% 0.1% 3.1% 2.1% 4.2%
5 1.1% 0.6% 0.2% 3.2% 2.6% 3.6%
6 1.4% 0.5% 0.1% 3.5% 2.8% 4.3%
7 1.3% 0.4% 0.2% 3.2% 2.6% 3.8%
8 1.3% 0.5% 0.1% 3.1% 2.5% 3.6%
9 1.4% 0.5% 0.1% 2.8% 2.4% 3.5%
10 1.5% 0.6% 0.2% 2.6% 2.1% 3.1%
11 1.5% 0.9% 0.2% 2.3% 1.9% 2.6%
12 1.3% 1.2% 0.2% 2.6% 2.5% 2.8%
13 1.5% 1.8% 0.2% 2.5% 2.0% 3.1%
14 1.3% 2.3% 0.2% 2.1% 1.3% 2.6%
15 1.4% 1.9% 0.2% 1.8% 1.6% 1.9%
16 1.2% 1.9% 0.1% 2.0% 1.5% 2.4%
17 1.2% 1.6% 0.2% 1.7% 1.4% 2.3%
18 N/A 1.4% 0.2% 1.5% 1.2% 2.1%
19 N/A 1.3% 0.1% N/A N/A N/A
20 N/A 1.2% 0.2% N/A N/A N/A
21 N/A 1.2% 0.1% N/A N/A N/A
22 N/A 1.2% 0.1% N/A N/A N/A
23 N/A 1.2% 0.1% N/A N/A N/A
24 N/A 1.3% 0.1% N/A N/A N/A
25 N/A 1.3% 0.1% N/A N/A N/A
26 N/A 1.8% 0.2% N/A N/A N/A
27 N/A 2.0% 0.1% N/A N/A N/A
28 N/A 1.9% 0.2% N/A N/A N/A
29 N/A 1.8% 0.2% N/A N/A N/A
30 N/A 1.6% 0.2% N/A N/A N/A
31 N/A 1.3% 0.2% N/A N/A N/A
32 N/A 1.2% 0.3% N/A N/A N/A
33 N/A 1.4% 0.3% N/A N/A N/A
34 N/A 1.3% 0.5% N/A N/A N/A

Influenza Outbreak Surveillance

In week 17, one laboratory-confirmed influenza outbreak in a LTC facility was reported.

To date this season (August 28, 2022 to April 29, 2023):

Outbreaks of ILI are not specific to any one respiratory pathogen and can be due influenza, or other respiratory viruses, including respiratory syncytial virus, rhinovirus, COVID-19, or a mixture of viruses. Many respiratory viruses in addition to the flu commonly circulate during the fall and winter, and can cause clusters of cases with respiratory illness which could be captured as ILI.

Number of provinces and territoriesFootnote 1 reporting in Week 17: 11 out of 13

Figure 7: Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2022-35 to 2023-17

Figure 7. Text version below.

Figure 7 - Text description
Surveillance Week Acute Care Facilities Long Term Care Facilities Other Schools and Daycares Remote and/or Isolated Communities
35 0 0 1 0 0
36 0 1 0 0 0
37 0 0 0 0 0
38 1 1 0 0 0
39 0 2 1 0 0
40 0 3 4 0 0
41 1 2 1 0 0
42 3 1 2 0 0
43 1 9 6 3 0
44 1 10 12 1 0
45 13 30 10 0 0
46 13 43 18 0 0
47 16 43 17 0 7
48 14 50 21 0 0
49 11 56 25 0 0
50 11 35 16 0 0
51 4 25 10 0 0
52 2 21 10 0 0
1 2 17 6 0 0
2 5 6 6 0 0
3 1 0 1 0 0
4 1 0 1 0 0
5 0 5 1 0 0
6 0 2 0 0 0
7 0 0 1 0 0
8 0 1 0 0 0
9 2 0 0 0 0
10 0 0 0 0 0
11 2 0 3 0 0
12 0 1 0 0 0
13 0 1 0 0 0
14 1 1 1 0 0
15 0 0 0 0 0
16 0 0 1 0 0
17 1 0 0 0 0

Influenza Severe Outcomes Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 17, eight influenza-associated hospitalizations and no ICU admissions were reported by participating provinces and territoriesFootnote 2. All but one hospitalization was due to influenza B.

To date this season (August 28, 2022 to April 29, 2023), 4,077 influenza-associated hospitalizations were reported by participating provinces and territories:

To date this season (August 28, 2022 to April 29, 2023), 348 ICU admissions and 268 influenza-associated deaths were reported.

Number of provinces and territories reporting in Week 17: 7 out of 9

Figure 8 – Cumulative rates of influenza-associated hospitalizations by age-group and surveillance week, Canada, participating provinces and territories, week 2022-35 to 2023-17

Figure 8. Text version below.

Figure 8 - Text description
Surveillance Week 0-4 yrs 5-19 yrs 20-44 yrs 45-64 yrs 65+ yrs Overall
35 0.2 0.1 0.0 0.0 0.1 0.1
36 0.2 0.1 0.0 0.0 0.3 0.1
37 0.2 0.1 0.0 0.1 0.6 0.2
38 0.2 0.1 0.0 0.1 0.7 0.2
39 0.2 0.1 0.0 0.1 1.1 0.3
40 0.2 0.1 0.1 0.2 1.1 0.3
41 0.2 0.1 0.1 0.2 1.7 0.4
42 0.7 0.1 0.2 0.4 2.0 0.6
43 2.7 1.2 0.4 0.9 3.4 1.3
44 8.7 3.1 1.0 1.9 6.3 2.9
45 19.7 6.4 2.2 4.4 16.1 6.8
46 35.6 9.6 4.2 6.8 29.1 11.7
47 56.1 15.1 7.0 11.7 47.0 19.1
48 73.1 18.1 10.3 17.2 69.0 26.8
49 89.7 21.2 12.5 22.1 87.7 33.4
50 102.9 23.3 15.0 25.4 102.8 38.7
51 110.3 24.0 16.1 27.1 112.6 41.8
52 114.3 24.2 16.6 28.7 120.2 43.9
1 116.5 24.4 16.9 29.9 125.9 45.4
2 117.6 24.5 17.1 30.3 128.0 46.0
3 118.1 24.9 17.2 30.6 128.7 46.3
4 118.8 25.0 17.3 30.7 129.5 46.6
5 119.2 25.2 17.4 30.9 129.9 46.8
6 119.4 25.3 17.5 31.1 130.4 47.0
7 119.9 25.3 17.5 31.2 130.5 47.1
8 120.5 25.3 17.7 31.4 130.8 47.3
9 120.5 25.3 17.8 31.5 131.0 47.4
10 121.0 25.5 17.9 31.5 131.2 47.5
11 121.9 25.7 18.0 31.6 131.3 47.7
12 122.6 25.8 18.1 31.8 131.6 47.9
13 123.9 25.9 18.2 31.9 132.0 48.1
14 124.3 26.1 18.4 32.0 132.2 48.3
15 124.6 26.2 18.5 32.1 132.5 48.4
16 125.5 26.2 18.6 32.2 132.8 48.5
17 126.0 26.2 18.7 32.3 133.0 48.7

Pediatric Influenza Hospitalizations and Deaths

In week 17, twenty influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network (Figure 9). All of the weekly hospitalizations were due to influenza B. Less than five influenza-associated ICU admissions were reported in week 17. No influenza-associated pediatric deaths have been reported since week 51 (mid December).

To date this season (August 28, 2022 to April 29, 2023):

Figure 9 – Number of pediatric (≤16 years of age) hospitalizations reported by the IMPACT network, by week, Canada, week 2022-35 to 2023-17

Figure 9. Text version below.

The shaded area represents the maximum and minimum number of hospitalizations, from seasons 2014-2015 to 2019-2020. Data from week 11 of the 2019-2020 season onwards are excluded from the historical comparison due to the COVID-19 pandemic.

Figure 9 - Text description
Surveillance week 2022-2023 2021-2022 Average Min Max
35 1 0 0 0 1
36 1 0 1 0 2
37 0 0 1 0 2
38 1 0 1 0 2
39 1 0 1 0 3
40 1 0 1 0 2
41 4 0 2 0 3
42 7 0 3 0 7
43 42 0 4 1 11
44 94 0 6 1 21
45 148 0 9 2 36
46 205 0 12 1 37
47 232 1 12 1 35
48 245 1 19 2 46
49 208 1 22 3 41
50 160 0 32 4 54
51 102 2 44 5 82
52 51 1 66 14 120
1 26 1 63 21 114
2 7 0 49 12 94
3 11 0 51 27 82
4 6 0 58 34 93
5 9 0 59 25 120
6 3 0 60 15 113
7 4 0 59 17 118
8 8 1 65 25 134
9 7 1 58 12 151
10 7 0 54 17 135
11 8 0 51 16 118
12 9 0 39 13 87
13 19 8 32 15 66
14 20 7 29 12 56
15 16 18 25 11 56
16 23 19 23 11 41
17 20 23 19 9 37
18 N/A 48 16 8 28
19 N/A 36 11 5 19
20 N/A 29 10 0 18
21 N/A 32 6 4 9
22 N/A 14 6 1 9
23 N/A 16 3 1 7
24 N/A 12 3 1 6
25 N/A 9 2 0 5
26 N/A 6 1 0 3
27 N/A 3 1 0 2
28 N/A 7 1 0 2
29 N/A 2 1 0 3
30 N/A 3 1 0 1
31 N/A 1 0 0 0
32 N/A 0 0 0 0
33 N/A 1 0 0 2
34 N/A 0 1 0 2
Figure 10 – Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by age-group reported by the IMPACT network, Canada, week 2022-35 to 2023-17

Figure 10. Text version below.

Figure 10 - Text description
Age Group Total
0-5 mo 187
6-23 mo 316
2-4 yr 526
5-9 yr 427
10-16 yr 250

Influenza Strain Characterization

Since September 1, 2022, the National Microbiology Laboratory (NML) has characterized 480 influenza viruses (399 A(H3N2), 45 A(H1N1), and 36 influenza B) received from Canadian laboratories.

Genetic Characterization of Influenza A(H3N2)

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

Sequence analysis of the HA genes of the viruses showed that they belonged to genetic group 3C.2a1b.2a2.

A/Darwin/6/2021 (H3N2)-like virus is an influenza A/H3N2 component of the 2022-23 Northern Hemisphere influenza vaccine and belongs to genetic group 3C.2a1b.2a2.

Antigenic Characterization

Influenza A(H3N2)

Influenza A(H1N1)

Influenza B

Antiviral Resistance

The NML also tests influenza viruses received from Canadian laboratories for antiviral resistance.

Oseltamivir

434 influenza viruses (365 A(H3N2), 43 A(H1N1) and 26 influenza B) were tested for resistance to oseltamivir and it was found that:

Zanamivir

434 influenza viruses (365 A(H3N2), 43 A(H1N1) and 26 influenza B) were tested for resistance to zanamivir and it was found that:

Influenza Vaccine Monitoring

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

Vaccination Coverage

The Seasonal Influenza Immunization Vaccination Coverage Survey is an annual telephone survey conducted between January and February that collects information from Canadians on whether they received the annual seasonal influenza vaccine that season. Vaccination coverage is measured as the percentage of people who reported receiving the influenza vaccine in a specific influenza season.

In the 2022-2023 influenza season, coverage was slightly higher compared to the 2021-2022 season at:

Table 1 – Seasonal influenza vaccination coverage, by risk group and influenza season, Seasonal Influenza Vaccination Coverage Survey, Canada, 2020-2021 to 2022-2023
Flu Season
  2022-2023 2021-2022 2020-2021
Age group (years) n Vaccination coverage
% (95% CI)
n Vaccination coverage
% (95% CI)
n Vaccination coverage
% (95% CI)
All adults (≥18) 3535 43.5 (41.6-45.3) 3487 38.7 (36.9-40.6) 3014 40.4 (38.4-42.4)
18-64, without chronic medical condition 1715 31.0 (28.6-33.4) 1658 26.8 (24.4-29.2) 1498 29.2 (26.6-31.8)
18-64, with chronic medical condition 583 43.1 (38.6-47.6) 713 37.6 (33.6-41.7) 646 40.5 (36.2-44.8)
Seniors (≥65) 1198 73.7 (71.0-76.5) 1098 71.0 (68.1-74.0) 862 70.4 (67.1-73.8)

Vaccine Effectiveness

The Canadian Sentinel Practitioner Surveillance Network (SPSN) provides estimates of the effectiveness of the seasonal influenza vaccine in preventing medically-attended illness due to laboratory-confirmed influenza among Canadians.

Based on data collected between November 1, 2022 and January 6, 2023, vaccine effectiveness (VE) was estimated to be 54% against influenza A(H3N2). Due to the dominant circulation of influenza A(H3N2) this season, the VE estimate was only available for one influenza subtype. By age group, VE was 47% (95% CI 11 to 69) for individuals under the age of 19 years, 58% (95% CI 33 to 73) for adults aged 20-64 years and 59% (95% CI 15 to 80) for adults 65 years and older. The SPSN interim estimates are published and available online.

Updated influenza VE estimates, if available, will be published at the end of the 2022-2023 influenza season.

Provincial and International Surveillance Links

See Influenza surveillance resources

Notes

The data in the FluWatch report represent surveillance data available at the time of writing. All data are preliminary and may change as updates are received.

To learn more about the FluWatch program, see the Overview of influenza monitoring in Canada page.

For more information on the flu, see our Flu (influenza) web page.

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

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

Ce rapport est disponible dans les deux langues officielles.

Footnote 1

All Provinces and Territories (PTs) participate in the FluWatch outbreak surveillance system. This outbreak system monitors influenza and ILI outbreaks in long-term care facilities (LTCF), acute care facilities, schools and daycares, remote and/or isolated communities, and facilities categorized as 'other'. Not all reporting PTs report outbreaks in all these settings. All PTs report laboratory confirmed outbreaks in LTCF. Four PTs (NB, NL, NS and YK) report ILI outbreaks in schools and/or daycares and other facilities.

Return to footnote 1 referrer

Footnote 2

Influenza-associated hospitalizations are reported by Alberta, Manitoba, New Brunswick, Newfoundland and Labrador, Northwest Territories, Nova Scotia, Prince Edward Island and Yukon. Only hospitalizations that require intensive medical care are reported by Saskatchewan.

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