FluWatch report: February 26 to March 4, 2023 (week 9)

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Organization: Public Health Agency of Canada

Published: 2023-03-10

Weekly Highlights

  • At the national level, influenza activity remains low at levels typically seen in late spring/early summer. Influenza activity continues to be reported in almost all provinces.

Virologic

  • In week 9, the percentage of tests positive for influenza was 1.3% and a total of 326 laboratory detections (173 influenza B and 153 influenza A) were reported. Influenza A and B are circulating at similar levels.
  • Among subtyped influenza A detections in week 9, 63% (25) were influenza A(H1N1).

Syndromic

  • The percentage of visits for influenza-like illness (ILI) was 0.7% in week 9. The percentage visits for ILI is below levels typical of this time of year.
  • The percentage of FluWatchers reporting fever and cough was 1.4% in week 9, below levels typical of this time of year.

Outbreaks

  • From August 28, 2022 to March 4, 2023 (weeks 35 to 9), 606 laboratory-confirmed influenza outbreaks have been reported (two new laboratory-confirmed influenza outbreaks were reported in week 9).

Severe Outcomes

  • The highest cumulative hospitalization rate up to week 9 is among adults 65 years of age and older (131/100,000 population) and children under 5 years of age (121/100,000 population). The overall cumulative hospitalization rate this season to date is 47/100,000 population.

Other Notes

  • The World Health Organization has released its recommended composition of the northern hemisphere influenza vaccine for use in the upcoming 2023-2024 season. The recommended strains were changed for the A(H1N1) component compared to the current 2022-2023 northern hemisphere vaccine.

On this page

Influenza/Influenza-like Illness Activity - Geographic Spread

In week 9, 33 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 16 regions in Canada reported no activity this week.

Figure 1 - Map of influenza/ILI activity by province and territory, Canada, week 2023-09

Number of Regions Reporting in Week 9: 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 Sporadic
P.E.I. Prince Edward Island Sporadic
N.S. Zone 1 - Western No Data
N.S. Zone 2 - Northern No Data
N.S. Zone 3 - Eastern No Data
N.S. Zone 4 - Central No Data
N.B. Region 1 No Activity
N.B. Region 2 No Activity
N.B. Region 3 No Activity
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 Localized
Ont. Toronto Localized
Man. Northern Regional Sporadic
Man. Prairie Mountain No Activity
Man. Interlake-Eastern Sporadic
Man. Winnipeg Sporadic
Man. Southern Health No Activity
Sask. North Sporadic
Sask. Central Sporadic
Sask. South Sporadic
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 Sporadic
Y.T. Yukon Sporadic
N.W.T. North No Activity
N.W.T. South No Activity
Nvt. Qikiqtaaluk Localized
Nvt. Kivalliq No Activity
Nvt. Kitimeot No Activity

Laboratory-Confirmed Influenza Detections

In week 9, the weekly percentage of tests positive for influenza was 1.3% and is at interseasonal levels.

The following results were reported from sentinel laboratories across Canada in week 9 (Figures 2 and 3):

To date this season (August 28, 2022 to March 4, 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 2023-09

Number of Laboratories Reporting in Week 9: 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 20 125 0.6 0.5
9 100 15 25 173 0.6 0.7
Figure 3 - Percentage of tests positive in Canada compared to previous seasons, week 2022-35 to 2023-09
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 11 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 12.6 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 N/A 0.2 0.0 36.0 16.0 23.2
11 N/A 0.3 0.0 31.4 16.2 21.4
12 N/A 0.9 0.0 30.0 15.0 20.1
13 N/A 1.5 0.0 28.3 14.5 19.6
14 N/A 2.5 0.0 23.2 12.7 17.9
15 N/A 3.9 0.0 20.7 11.9 16.3
16 N/A 7.0 0.0 18.5 11.6 14.5
17 N/A 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 2023-09

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 98.6% 1.4% 8357
5 to 19 98.3% 1.7% 10736
20 to 44 97.6% 2.4% 9588
45 to 64 99.1% 0.9% 6116
65+ 99.6% 0.4% 11881
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 5.4% 94.6% 2836
5 to 19 4.5% 95.5% 3566
20 to 44 8.9% 91.1% 2875
45 to 64 16.2% 83.8% 1844
65+ 8.8% 91.2% 3583

Syndromic / Influenza-like Illness Surveillance

Healthcare Practitioners Sentinel Surveillance

In week 9, 0.7% of visits to healthcare professionals were due to influenza-like illness (ILI) (Figure 5). The percentage of visits for ILI is below 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 2023-09

Number of Sentinels Reporting in Week 9: 37

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 11 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 0.7% 0.7% 0.2% 2.3% 0.9% 3.1%
10 N/A 0.9% 0.2% 2.0% 1.0% 2.8%
11 N/A 0.6% 0.2% 1.9% 1.1% 2.8%
12 N/A 0.8% 0.3% 1.6% 0.6% 2.6%
13 N/A 1.2% 0.4% 1.6% 1.1% 2.6%
14 N/A 1.1% 0.2% 1.7% 1.1% 3.0%
15 N/A 1.2% 0.3% 1.3% 0.9% 1.9%
16 N/A 1.5% 0.3% 1.2% 0.8% 1.7%
17 N/A 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 9, 9,937 participants reported to FluWatchers, of which 1.4% reported symptoms of cough and fever (Figure 6). The percentage of FluWatchers who have reported cough and fever is well 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 137 participants who reported cough and fever:

The Northwest Territories had the highest participation rate this week (57 participants per 100,000 population) and the neighbourhood with postal code, K0A had the highest number of participants (127). 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 2023-09

Number of Participants Reporting in Week 9: 9,937

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 11 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 N/A 0.5% 0.1% 3.1% 2.5% 3.6%
9 1.4% 0.5% 0.1% 2.8% 2.4% 3.5%
10 N/A 0.6% 0.2% 2.6% 2.1% 3.1%
11 N/A 0.9% 0.2% 2.3% 1.9% 2.6%
12 N/A 1.2% 0.2% 2.6% 2.5% 2.8%
13 N/A 1.8% 0.2% 2.5% 2.0% 3.1%
14 N/A 2.3% 0.2% 2.1% 1.3% 2.6%
15 N/A 1.9% 0.2% 1.8% 1.6% 1.9%
16 N/A 1.9% 0.1% 2.0% 1.5% 2.4%
17 N/A 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 9, two laboratory-confirmed influenza A outbreaks in acute care facilities were reported.

To date this season (August 28, 2022 to March 4, 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 9: 12 out of 13

Figure 7: Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2022-35 to 2023-09

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 0 2 0 0
43 1 7 6 3 0
44 1 10 12 1 0
45 13 27 10 0 0
46 12 37 18 0 0
47 15 38 17 0 7
48 13 44 22 0 0
49 10 53 24 0 0
50 10 32 16 0 0
51 3 23 10 0 0
52 2 20 10 0 0
1 2 17 6 0 0
2 5 5 6 0 0
3 1 0 1 0 0
4 1 0 1 0 0
5 0 5 1 0 0
6 0 1 0 0 0
7 0 0 1 0 0
8 0 1 0 0 0
9 2 0 0 0 0

Influenza Severe Outcomes Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 9, two influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote 2.

To date this season (August 28, 2022 to March 4, 2023), 3,951 influenza-associated hospitalizations were reported by participating provinces and territories:

To date this season (August 28, 2022 to March 4, 2023), 332 ICU admissions and 266 influenza-associated deaths were reported.

Number of provinces and territories reporting in Week 9: 8 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 2023-09

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 0.9 1.9 6.3 2.9
45 19.7 6.3 2.2 4.4 16.0 6.8
46 35.6 9.4 4.2 6.8 29.1 11.7
47 56.1 14.9 7.0 11.7 46.6 18.9
48 73.1 17.9 10.3 17.1 68.4 26.6
49 89.5 21.0 12.5 22.1 87.0 33.2
50 102.9 23.2 14.9 25.3 101.8 38.5
51 110.3 23.9 16.1 27.0 111.5 41.5
52 114.3 24.2 16.6 28.6 119.2 43.7
1 116.5 24.4 16.8 29.8 124.8 45.2
2 117.6 24.4 17.0 30.1 126.6 45.7
3 118.1 24.8 17.1 30.4 127.3 46.0
4 118.8 24.9 17.2 30.6 128.0 46.3
5 119.2 25.1 17.4 30.8 128.4 46.5
6 119.4 25.2 17.5 30.9 128.7 46.7
7 119.7 25.3 17.5 31.0 128.9 46.7
8 121.0 25.4 17.6 31.2 129.8 47.1
9 120.7 25.4 17.7 31.4 131.2 47.3

Pediatric Influenza Hospitalizations and Deaths

In week 9, six influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network (Figure 9). The majority of the weekly hospitalizations were due to influenza B (67%). One influenza-associated ICU admission was reported in week 9. No influenza-associated pediatric deaths have been reported since week 50 (mid December).

To date this season (August 28, 2022 to March 4, 2023):

Figure 9 – Number of pediatric (≤16 years of age) hospitalizations reported by the IMPACT network, by week, Canada, week 2022-35 to 2023-09

Figure 9. Text version below.

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 41 0 4 1 11
44 92 0 6 1 21
45 140 0 9 2 36
46 196 0 12 1 37
47 228 1 12 1 35
48 246 1 19 2 46
49 200 1 22 3 41
50 163 0 32 4 54
51 101 2 44 5 82
52 49 1 66 14 120
1 28 1 63 21 114
2 8 0 49 12 94
3 10 0 51 27 82
4 3 0 58 34 93
5 7 0 59 25 120
6 3 0 60 15 113
7 4 0 59 17 118
8 7 1 65 25 134
9 6 1 58 12 151
10 N/A 0 54 17 135
11 N/A 0 51 16 118
12 N/A 0 39 13 87
13 N/A 8 32 15 66
14 N/A 7 29 12 56
15 N/A 18 25 11 56
16 N/A 19 23 11 41
17 N/A 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 2023-09

Figure 10. Text version below.

Figure 10 - Text description
Age Group Total
0-5 mo 174
6-23 mo 284
2-4 yr 481
5-9 yr 374
10-16 yr 236

Influenza Strain Characterization

Since September 1, 2022, the National Microbiology Laboratory (NML) has characterized 373 influenza viruses (334 A(H3N2), 31 A(H1N1), and 3 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

324 influenza viruses (289 A(H3N2), 32 A(H1N1) and 3 influenza B) were tested for resistance to oseltamivir and it was found that:

Zanamivir

324 influenza viruses (289 A(H3N2), 32 A(H1N1) and 3 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 vaccine coverage and effectiveness.

Vaccine Coverage

Influenza vaccine coverage estimates for the 2022-2023 season are anticipated to be available in February or March 2023.

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.

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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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