FluWatch report: January 1 to January 7, 2023 (week 1)

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 1, almost all regions in Canada reported either sporadic or localized influenza activity (Figure 1).

Number of Regions Reporting in week 1: 53 out of 53

Figure 1 - Text description

Province	Influenza Surveillance Region	Activity Level
N.L.	Eastern	Localized
N.L.	Labrador-Grenfell	Sporadic
N.L.	Central	Localized
N.L.	Western	Sporadic
P.E.I.	Prince Edward Island	Sporadic
N.S.	Zone 1 - Western	Localized
N.S.	Zone 2 - Northern	Sporadic
N.S.	Zone 3 - Eastern	Localized
N.S.	Zone 4 - Central	Localized
N.B.	Region 1	Localized
N.B.	Region 2	Sporadic
N.B.	Region 3	Sporadic
N.B.	Region 4	Sporadic
N.B.	Region 5	Sporadic
N.B.	Region 6	Sporadic
N.B.	Region 7	Sporadic
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	Localized
Ont.	North West	Localized
Ont.	South West	Localized
Ont.	Toronto	Localized
Man.	Northern Regional	Sporadic
Man.	Prairie Mountain	Sporadic
Man.	Interlake-Eastern	Sporadic
Man.	Winnipeg	Sporadic
Man.	Southern Health	Sporadic
Sask.	North	Sporadic
Sask.	Central	Sporadic
Sask.	South	Sporadic
Alta.	North Zone	Localized
Alta.	Edmonton	Sporadic
Alta.	Central Zone	Localized
Alta.	Calgary	Sporadic
Alta.	South Zone	Sporadic
B.C.	Interior	Sporadic
B.C.	Fraser	Sporadic
B.C.	Vancouver Coastal	Localized
B.C.	Vancouver Island	Sporadic
B.C.	Northern	Sporadic
Y.T.	Yukon	Localized
N.W.T.	North	Sporadic
N.W.T.	South	Sporadic
Nvt.	Qikiqtaaluk	Sporadic
Nvt.	Kivalliq	Sporadic
Nvt.	Kitimeot	No Activity

Laboratory-Confirmed Influenza Detections

In week 1, the weekly percentage of tests positive for influenza has decreased from the previous week (8.0% in week 52 to 4.6% in week 1) to below expected pre-pandemic levels, and is approaching interseasonal levels.

The following results were reported from sentinel laboratories across Canada in week 1 (Figures 2 and 3):

• A total of 1,749 laboratory detections (1,721 influenza A and 28 influenza B) were reported.
• Among subtyped influenza A detections, 77% (266) were influenza A(H3N2) and 23% (80) were influenza A(H1N1).
• Among detections for which age information was reported (1,181), 561 (48%) of detections were in individuals aged 65+ years old. The proportion among adults, particularly seniors aged 65+, has increased (from 40% in week 52), whereas the proportion of detections among individuals aged 0-19 years old has decreased (25% in week 52 to 19% in week 1).

To date this season (August 28, 2022 to January 7, 2023):

• 62,904 influenza detections were reported, of which 99% (62,670) were influenza A and among subtyped influenza A detections (19,729), influenza A(H3N2) accounted for 94% of detections.
• 40,134 laboratory-confirmed influenza detections with age information were reported, of which 16,524 (41%) 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 1: 33 out of 35

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	5918	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	5697	1494	137	29	17.2	0.1
51	3781	828	155	19	12.5	0.1
52	2288	472	104	28	8.0	0.1
1	1319	266	80	28	4.6	0.1

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	12.5	0.2	0.0	29.1	3.3	20.1
52	8.0	0.1	0.0	34.5	4.3	24.5
1	4.6	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	99.5%	0.5%	7273
5 to 19	99.8%	0.2%	9251
20 to 44	99.4%	0.6%	7967
45 to 64	99.7%	0.3%	5175
65+	99.7%	0.3%	10468

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	4.6%	95.4%	2797
5 to 19	3.9%	96.1%	3525
20 to 44	7.8%	92.2%	2797
45 to 64	14.1%	85.9%	1761
65+	7.3%	92.7%	3431

Syndromic / Influenza-like Illness Surveillance

Healthcare Practitioners Sentinel Surveillance

In week 1, 1.7% of visits to healthcare professionals were due to influenza-like illness (ILI) (Figure 5). The percentage of visits for ILI is slightly 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.

Number of Sentinels Reporting in Week 1: 35

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	2.8%	1.5%	0.5%	2.0%	1.0%	3.1%
1	1.7%	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 1, 10,736 participants reported to FluWatchers, of which 1.7% 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 178 participants who reported cough and fever:

• 24% consulted a healthcare professional;
• 71% reported days missed from work or school, resulting in an average of 2.8 missed days from work or school among those 126 participants.

The neighbourhood with postal code, K0A had the highest number of participants (142). 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 1: 10,736

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	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 1, 16 laboratory-confirmed influenza outbreaks were reported in Canada (11 in long-term care facilities (LTC), 3 in facilities categorized as 'other', and 2 in acute care facilities). All outbreaks were due to influenza A.

To date this season (August 28, 2022 to January 7, 2023):

• 572 laboratory-confirmed influenza outbreaks have been reported
  • 316 were in LTC facilities (55%)
  • 156 were in facilities categorized as 'other' (27%)
  • 89 were in acute care facilities (16%)
  • 7 were in remote and/or isolated communities (1%)
  • 4 were in schools/daycares (<1%)
  • All but one outbreak was due to influenza A
• 231 ILI outbreaks have been reported
  • All but 3 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, 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 territories^{Footnote 1} reporting in Week 1: 13 out of 13

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	8	5	3	0
44	1	10	12	1	0
45	13	26	10	0	0
46	13	42	20	0	0
47	16	41	17	0	7
48	13	49	20	0	0
49	11	53	26	0	0
50	9	29	17	0	0
51	4	22	9	0	0
52	1	15	8	0	0
1	2	11	3	0	0

Influenza Severe Outcomes Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 1, 87 influenza-associated hospitalizations and 4 ICU admissions were reported by participating provinces and territories^{Footnote 2}. This week, 5 influenza-associated deaths were reported.

To date this season 3,690 influenza-associated hospitalizations were reported (August 28, 2022 to January 7, 2023) by participating provinces and territories:

• >99% of the hospitalizations were associated with influenza A.
• Of the cases with subtype information (1,906), 91% were associated with influenza A(H3N2)
• The highest cumulative hospitalization rates up to week 1 were among adults 65 years of age and older (120/100,000 population) and children under 5 years of age (116/100,000 population).

To date this season (August 28, 2022 to January 7, 2023), 311 ICU admissions and 218 influenza-associated deaths were reported.

Number of provinces and territories reporting in Week 1: 9 out of 9

Figure 8 - Text description

Surveillance Week	0-4 yrs	5-19 yrs	20-44 yrs	45-64 yrs	65+ yrs	Overall
35	0.2	0.0	0.0	0.0	0.1	0.1
36	0.2	0.0	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	15.9	6.8
46	35.6	9.5	4.2	6.8	28.9	11.7
47	56.1	14.8	7.0	11.6	46.4	18.9
48	73.1	17.7	10.3	17.0	67.8	26.5
49	89.5	20.8	12.5	21.9	85.9	33.0
50	103.1	23.0	14.9	25.0	100.3	38.1
51	110.7	23.7	15.9	26.6	109.4	41.0
52	114.5	24.0	16.4	28.1	116.5	43.0
1	116.1	24.0	16.5	29.0	120.4	44.0

Pediatric Influenza Hospitalizations and Deaths

In week 1, 30 influenza-associated pediatric (≤16 years of age) hospitalizations and 3 ICU admissions were reported by the Immunization Monitoring Program Active (IMPACT) network. The number of weekly influenza-associated hospitalizations is within levels typical of this time of year (Figure 9). All but one hospitalisation reported in week 1 were associated with influenza A. This week, no influenza-associated pediatric deaths were reported.

To date this season (August 28, 2022 to January 7, 2023):

• 1,534 pediatric influenza-associated hospitalizations have been reported.
• Children aged between 2-4 years and 5-9 years account for more than 55% of the reported pediatric hospitalizations (Figure 10).
• 188 ICU admissions were reported; children aged between 2-4 years and 5-9 years account for more than 50% of the reported pediatric ICU admissions.
• 7 influenza-associated pediatric deaths have been reported.

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	80	0	6	1	21
45	153	0	9	2	36
46	197	0	12	1	37
47	228	1	12	1	35
48	251	1	19	2	46
49	209	1	22	3	41
50	176	0	32	4	54
51	104	2	44	5	82
52	49	1	66	14	120
1	30	1	63	21	114
2	N/A	0	49	12	94
3	N/A	0	51	27	82
4	N/A	0	58	34	93
5	N/A	0	59	25	120
6	N/A	0	60	15	113
7	N/A	0	59	17	118
8	N/A	1	65	25	134
9	N/A	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 - Text description

Age Group	Total
0-5 mo	165
6-23 mo	282
2-4 yr	486
5-9 yr	369
10-16 yr	232

Influenza Strain Characterization

Since September 1, 2022, the National Microbiology Laboratory (NML) has characterized 238 influenza viruses (219 A(H3N2), 19 A(H1N1)) received from Canadian laboratories.

Genetic Characterization of Influenza A(H3N2)

Three 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)

• Of the 216 influenza A (H3N2) viruses characterized, 213 were characterized as antigenically similar to A/Darwin/6/2021 (H3N2)-like virus with antisera raised against cell-grown A/Darwin/6/2021 (H3N2)-like virus. Three viruses showed reduced titer with antisera raised against cell-grown A/Darwin/6/2021 (H3N2)-like virus.
  • A/Darwin/6/2021 (H3N2)-like virus is an influenza A/H3N2 component of the 2022-23 Northern Hemisphere influenza vaccine.
• Of the 216 influenza A (H3N2) viruses characterized, 189 belonged to genetic group 3C.2a1b.2a2. Sequences are pending for the remaining viruses.

Influenza A(H1N1)

• 19 influenza A (H1N1) viruses were 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

175 influenza viruses (160 A(H3N2) and 15 A(H1N1)) were tested for resistance to oseltamivir and it was found that:

• All influenza viruses were sensitive to oseltamivir.

Zanamivir

175 influenza viruses (160 A(H3N2) and 15 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.