FluWatch report: October 30 to November 5, 2022 (week 44)

On this page

• Influenza/Influenza-like Illness Activity - Geographic Spread
• Laboratory-Confirmed Influenza Detections
• Syndromic / Influenza-like Illness Surveillance
• Influenza Outbreak Surveillance
• Influenza Severe Outcomes Surveillance
• Influenza Strain Characterization
• Antiviral Resistance
• Influenza Vaccine Monitoring
• Provincial and International Influenza Reports

Influenza/Influenza-like Illness Activity - Geographic Spread

In week 44, nine regions in four provinces (N.B., Ont., Sask., and Alta.) reported localized activity and 22 regions in eight provinces reported sporadic influenza activity (N.L., P.E.I., N.S., N.B., Que., Ont., Sask. and Alta.) (Figure 1).

Number of Regions Reporting in Week 44: 40 out of 53

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	Sporadic
N.S.	Zone 2 - Northern	Sporadic
N.S.	Zone 3 - Eastern	No Activity
N.S.	Zone 4 - Central	Sporadic
N.B.	Region 1	Localized
N.B.	Region 2	Localized
N.B.	Region 3	Localized
N.B.	Region 4	Sporadic
N.B.	Region 5	No Activity
N.B.	Region 6	Sporadic
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	Localized
Ont.	Eastern	Localized
Ont.	North East	Sporadic
Ont.	North West	Sporadic
Ont.	South West	Sporadic
Ont.	Toronto	Localized
Man.	Northern Regional	No Data
Man.	Prairie Mountain	No Data
Man.	Interlake-Eastern	No Data
Man.	Winnipeg	No Data
Man.	Southern Health	No Data
Sask.	North	Localized
Sask.	Central	Sporadic
Sask.	South	Sporadic
Alta.	North Zone	Sporadic
Alta.	Edmonton	Sporadic
Alta.	Central Zone	Sporadic
Alta.	Calgary	Localized
Alta.	South Zone	Sporadic
B.C.	Interior	No Data
B.C.	Fraser	No Data
B.C.	Vancouver Coastal	No Data
B.C.	Vancouver Island	No Data
B.C.	Northern	No Data
Y.T.	Yukon	No Activity
N.W.T.	North	No Activity
N.W.T.	South	No Activity
Nvt.	Qikiqtaaluk	No Data
Nvt.	Kivalliq	No Data
Nvt.	Kitimeot	No Data

Laboratory-Confirmed Influenza Detections

In week 44, a total of 2,234 laboratory detections (2,231 influenza A and 3 influenza B) were reported. Influenza activity has crossed the seasonal threshold, indicating the start of an influenza epidemic at the national level.

The following results were reported from sentinel laboratories across Canada in week 44 (Figures 2 and 3):

• The weekly percentage of tests positive for influenza increased from 6.3% in week 43 to 11.7% in week 44 and is above expected pre-pandemic levels.
• Among subtyped influenza A detections, 96% (1,149) were influenza A(H3N2) and 4% (44) were influenza A(H1N1).
• Among detections for which age information was reported (1,197), 739 (64%) of detections were in individuals aged 0-19 years old.

To date this season (August 28, 2022 to November 5, 2022):

• 4,480 influenza detections were reported, of which 99% (4,439) were influenza A and among subtyped influenza A detections (2,394), influenza A(H3N2) accounted for 93% of detections.
• 2,473 laboratory-confirmed influenza detections with age information were reported, of which 1,439 (58%) were in individuals aged 0-19 years old (Figure 4).

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.

Number of Laboratories Reporting in Week 44: 32 out of 34

Figure 2 - Text description

Surveillance Week	A(Unsubtyped)	A(H3N2)	A(H1N1)	Influenza B	Percent Positive A	Percent Positive B
35	12	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	34	20	3	0.5	0.0
39	44	53	22	5	0.7	0.0
40	63	66	16	4	1.0	0.0
41	129	109	20	1	1.5	0.0
42	246	202	11	9	2.7	0.1
43	495	524	15	6	6.4	0.0
44	1083	1149	44	3	11.6	0.0

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	2.7	0.1	0.0	3.4	0.9	2.2
43	6.5	0.1	0.0	5.3	0.8	2.8
44	11.7	0.2	0.1	8.5	1.2	3.7
45	N/A	0.1	0.0	10.1	1.4	4.6
46	N/A	0.2	0.0	14.1	1.5	6.1
47	N/A	0.2	0.1	15.4	1.4	7.7
48	N/A	0.3	0.1	18.2	0.8	10.6
49	N/A	0.3	0.0	19.7	1.6	13.0
50	N/A	0.3	0.0	27.0	2.4	16.8
51	N/A	0.2	0.0	29.1	3.3	20.1
52	N/A	0.1	0.0	34.5	4.3	24.5
1	N/A	0.1	0.0	31.7	5.8	23.4
2	N/A	0.1	0.0	29.1	7.1	23.0
3	N/A	0.1	0.0	30.1	12.2	23.6
4	N/A	0.1	0.0	29.5	15.9	24.0
5	N/A	0.0	0.0	30.6	19.6	24.9
6	N/A	0.1	0.0	32.4	17.9	25.0
7	N/A	0.0	0.0	32.5	16.3	25.1
8	N/A	0.1	0.0	32.9	17.5	25.1
9	N/A	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

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	98.9%	1.1%	440
5 to 19	99.6%	0.4%	999
20 to 44	97.9%	2.1%	419
45 to 64	100.0%	0.0%	220
65+	99.5%	0.5%	395

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	4.5%	95.5%	331
5 to 19	4.1%	95.9%	728
20 to 44	7.1%	92.9%	312
45 to 64	13.3%	86.7%	143
65+	7.4%	92.6%	282

Syndromic / Influenza-like Illness Surveillance

Healthcare Practitioners Sentinel Surveillance

In week 44, 1.2% of visits to healthcare professionals were due to influenza-like illness (ILI). The percentage of visits for ILI is above average but within levels typical of this time of year.

Since the beginning of the surveillance season, the percentage of visits for ILI has been within or near expected pre-pandemic levels (Figure 5). 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 even SARS-CoV-2, the virus that causes COVID-19.

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.

Number of Sentinels Reporting in Week 44: 51

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	1.2%	0.6%	0.3%	1.2%	0.7%	1.7%
45	N/A	1.0%	0.4%	1.2%	0.9%	1.5%
46	N/A	0.9%	0.8%	1.4%	1.2%	1.8%
47	N/A	0.7%	0.3%	1.6%	1.1%	2.2%
48	N/A	1.1%	0.5%	1.5%	1.1%	2.2%
49	N/A	0.9%	0.5%	1.7%	1.0%	2.8%
50	N/A	1.1%	0.4%	1.5%	1.1%	1.7%
51	N/A	1.7%	0.5%	1.9%	1.4%	2.7%
52	N/A	1.5%	0.5%	2.0%	1.0%	3.1%
1	N/A	2.1%	0.7%	3.4%	1.9%	5.4%
2	N/A	1.6%	0.4%	3.4%	1.8%	5.7%
3	N/A	1.4%	0.2%	2.3%	1.3%	3.7%
4	N/A	0.9%	0.3%	2.0%	1.1%	2.9%
5	N/A	1.0%	0.2%	2.1%	1.4%	3.1%
6	N/A	0.7%	0.5%	2.4%	1.4%	4.0%
7	N/A	0.7%	0.3%	2.4%	0.9%	3.5%
8	N/A	0.8%	0.2%	2.3%	0.8%	3.4%
9	N/A	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 44, 10,732 participants reported to FluWatchers, of which 2.6% reported symptoms of cough and fever (Figure 6). The percentage of FluWatchers who have reported cough and fever has increased in recent weeks and is well above expected levels typical of this time of year.

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 even SARS-CoV-2, the virus that causes COVID-19. FluWatchers reporting is not impacted by changes in health services or health seeking behaviours.

Among the 277 participants who reported cough and fever:

• 18% consulted a healthcare professional;
• 80% reported days missed from work or school, resulting in an average of 3.1 missed days from work or school among those 196 participants.

The Northwest Territories had the highest participation rate this week (58 participants per 100,000 population) and the neighbourhood with postal code, K0A had the highest number of participants (143). 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.

Number of Participants Reporting in Week 44: 10,732

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	N/A	0.5%	0.3%	1.8%	1.4%	2.3%
46	N/A	0.4%	0.3%	1.8%	1.2%	2.2%
47	N/A	0.6%	0.3%	1.9%	1.4%	2.4%
48	N/A	0.5%	0.3%	2.4%	1.7%	3.4%
49	N/A	0.4%	0.2%	2.6%	2.0%	3.2%
50	N/A	0.6%	0.1%	2.9%	2.1%	3.8%
51	N/A	1.0%	0.2%	3.2%	2.5%	3.9%
52	N/A	1.5%	0.1%	4.0%	2.8%	5.4%
1	N/A	1.1%	0.1%	3.8%	2.9%	4.8%
2	N/A	1.0%	0.2%	2.9%	1.9%	3.9%
3	N/A	0.8%	0.1%	3.3%	2.3%	4.8%
4	N/A	0.6%	0.1%	3.1%	2.1%	4.2%
5	N/A	0.6%	0.2%	3.2%	2.6%	3.6%
6	N/A	0.5%	0.1%	3.5%	2.8%	4.3%
7	N/A	0.4%	0.2%	3.2%	2.6%	3.8%
8	N/A	0.5%	0.1%	3.1%	2.5%	3.6%
9	N/A	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 44, 13 laboratory-confirmed influenza outbreaks were reported in Canada (9 in long-term care facilities (LTC), 1 in a school/daycare, and 3 in facilities categorized as 'other'). All outbreaks were due to influenza A. An additional three ILI outbreaks were reported in schools/daycares.
To date this season (August 28, 2022 to November 5, 2022):

• 35 laboratory-confirmed influenza outbreaks have been reported
  • 16 were in LTC facilities (46%)
  • 11 were in facilities categorized as 'other' (31%)
  • The remaining outbreaks were in either in acute care facilities (4) or schools/daycares (4)
  • All but one outbreak were due to influenza A
• 6 ILI outbreaks have been reported
  • All ILI outbreaks have been reported in schools and/or daycares.

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, and even COVID-19. 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 territories^{Footnote 1} reporting in week 44: 10 out of 13

Figure 7 - Text description

Surveillance week	2022-2023	2021-2022	Average	Min	Max
35	0	0	1	0	0
36	0	1	0	0	0
37	0	0	0	0	0
38	0	0	0	0	0
39	0	1	0	0	0
40	0	2	0	0	0
41	1	0	1	0	0
42	3	0	1	0	0
43	0	3	3	3	0
44	0	9	3	1	0
45	N/A	N/A	N/A	N/A	N/A
46	N/A	N/A	N/A	N/A	N/A
47	N/A	N/A	N/A	N/A	N/A
48	N/A	N/A	N/A	N/A	N/A
49	N/A	N/A	N/A	N/A	N/A
50	N/A	N/A	N/A	N/A	N/A
51	N/A	N/A	N/A	N/A	N/A
52	N/A	N/A	N/A	N/A	N/A
1	N/A	N/A	N/A	N/A	N/A
2	N/A	N/A	N/A	N/A	N/A
3	N/A	N/A	N/A	N/A	N/A
4	N/A	N/A	N/A	N/A	N/A
5	N/A	N/A	N/A	N/A	N/A
6	N/A	N/A	N/A	N/A	N/A
7	N/A	N/A	N/A	N/A	N/A
8	N/A	N/A	N/A	N/A	N/A
9	N/A	N/A	N/A	N/A	N/A
10	N/A	N/A	N/A	N/A	N/A
11	N/A	N/A	N/A	N/A	N/A
12	N/A	N/A	N/A	N/A	N/A
13	N/A	N/A	N/A	N/A	N/A
14	N/A	N/A	N/A	N/A	N/A
15	N/A	N/A	N/A	N/A	N/A
16	N/A	N/A	N/A	N/A	N/A
17	N/A	N/A	N/A	N/A	N/A
18	N/A	N/A	N/A	N/A	N/A
19	N/A	N/A	N/A	N/A	N/A
20	N/A	N/A	N/A	N/A	N/A
21	N/A	N/A	N/A	N/A	N/A
22	N/A	N/A	N/A	N/A	N/A
23	N/A	N/A	N/A	N/A	N/A
24	N/A	N/A	N/A	N/A	N/A
25	N/A	N/A	N/A	N/A	N/A
26	N/A	N/A	N/A	N/A	N/A
27	N/A	N/A	N/A	N/A	N/A
28	N/A	N/A	N/A	N/A	N/A
29	N/A	N/A	N/A	N/A	N/A
30	N/A	N/A	N/A	N/A	N/A
31	N/A	N/A	N/A	N/A	N/A
32	N/A	N/A	N/A	N/A	N/A
33	N/A	N/A	N/A	N/A	N/A
34	N/A	N/A	N/A	N/A	N/A

Influenza Severe Outcomes Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 44, 99 influenza-associated hospitalizations and five ICU admissions were reported by participating provinces and territories^{Footnote 2}.

To date this season 184 influenza-associated hospitalizations were reported (August 28, 2022 to November 5, 2022) by participating provinces and territories

• 99% of the hospitalizations were associated with influenza A.
• Of the cases with subtype information (132), 90% were associated with influenza A(H3N2)
• 34% of the hospitalizations were among individuals 65 years of age and older, followed by those 5 to 19 years of age (22%)

To date this season, 15 ICU admissions and less than five influenza-associated deaths were reported.

Number of provinces and territories reporting in week 44: 8 out of 9

Pediatric Influenza Hospitalizations and Deaths

In week 44, 78 influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. The number weekly influenza-associated hospitalizations are well above levels typical of this time of year (Figure 7). Children aged 2 to 4yrs and 10 to 16yrs each accounted 27% of the weekly hospitalizations followed by those aged 5-9yrs (24%).

To date this season (August 28, 2022 to November 5, 2022), 133 pediatric influenza-associated hospitalizations and 17 ICU admissions have been reported.

Figure 8 - Text description

Surveillance week	2022-2023	2021-2022	Average	Min	Max
35	0	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	40	0	4	1	11
44	72	0	6	1	21
45	#N/A	0	9	2	36
46	#N/A	0	12	1	37
47	#N/A	1	11	1	35
48	#N/A	1	20	2	46
49	#N/A	1	21	3	41
50	#N/A	0	31	4	54
51	#N/A	2	44	5	82
52	#N/A	1	63	14	103
1	#N/A	1	62	21	107
2	#N/A	0	50	12	100
3	#N/A	0	51	27	80
4	#N/A	0	58	34	90
5	#N/A	0	59	25	120
6	#N/A	0	60	15	115
7	#N/A	0	59	17	118
8	#N/A	1	65	25	134
9	#N/A	1	57	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	28	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

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.

Influenza Strain Characterization

Since September 1, 2022, the National Microbiology Laboratory (NML) has characterized 13 influenza viruses (12 A(H3N2), 1 A(H1N1)) received from Canadian laboratories.

Genetic Characterization of Influenza A(H3N2)

One influenza A(H3N2) virus 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 this virus.

Sequence analysis of the HA gene of the virus showed that it belonged to genetic group 3C.2a1b.2a2.

A/Darwyn/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)

• 11 influenza A (H3N2) viruses were characterized as antigenically similar to A/Darwyn/6/2021 (H3N2)-like virus with antisera raised against cell-grown A/Darwyn/6/2021 (H3N2)-like virus.
  • A/Darwyn/6/2021 (H3N2)-like virus is an influenza A/H3N2 component of the 2022-23 Northern Hemisphere influenza vaccine.
• Of the 11 influenza A (H3N2) viruses characterized, 7 viruses belonged to genetic group 3C.2a1b.2a2. Sequencing is pending for the remaining 4 viruses.

Influenza A(H1N1)

• One A(H1N1) virus was characterized as antigenically similar to A/Wisconsin/588/2019-like with ferret antisera produced against cell-propagated A/Wisconsin/588/2019.
  • A/Wisconsin/588/2019 is the influenza A/H1N1 component of the 2022-23 Northern Hemisphere influenza vaccine.

Antiviral Resistance

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

Oseltamivir

11 influenza viruses (10 A(H3N2) and 1 A(H1N1)) were tested for resistance to oseltamivir and it was found that:

• All influenza viruses were sensitive to oseltamivir.

Zanamivir

11 influenza viruses (10 A(H3N2) and 1 A(H1N1)) were tested for resistance to zanamivir and it was found that:

• All influenza viruses were sensitive to zanamivir.

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

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

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.