FluWatch report: March 13, 2022 to April 16, 2022 (weeks 11-15)

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 15, 30 regions in eleven provinces and territories (B.C., Y.T., N.W.T., Nvt., Alta., Sask., Man., Ont., Que., N.S., P.E.I.) reported sporadic influenza/ILI activity and five regions in two provinces (Alta., Ont.) reported localized influenza/ILI activity.  All other surveillance regions reported no influenza/ILI activity (Figure 1).

Number of Regions Reporting in Week 15: 42 out of 53

Figure 1 - Text description

Province	Influenza Surveillance Region	Activity Level
N.L.	Eastern	No Data
N.L.	Labrador-Grenfell	No Data
N.L.	Central	No Data
N.L.	Western	No Data
P.E.I.	Prince Edward Island	Sporadic
N.S.	Zone 1 - Western	No Activity
N.S.	Zone 2 - Northern	Sporadic
N.S.	Zone 3 - Eastern	Sporadic
N.S.	Zone 4 - Central	Sporadic
N.B.	Region 1	No Data
N.B.	Region 2	No Data
N.B.	Region 3	No Data
N.B.	Region 4	No Data
N.B.	Region 5	No Data
N.B.	Region 6	No Data
N.B.	Region 7	No Data
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	Sporadic
Ont.	Central West	Localized
Ont.	Eastern	Localized
Ont.	North East	Sporadic
Ont.	North West	Sporadic
Ont.	South West	Localized
Ont.	Toronto	Sporadic
Man.	Northern Regional	Sporadic
Man.	Prairie Mountain	No Activity
Man.	Interlake-Eastern	No Activity
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	Localized
Alta.	South Zone	Localized
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	Sporadic
Nvt.	Qikiqtaaluk	Sporadic
Nvt.	Kivalliq	No Activity
Nvt.	Kitimeot	No Activity

Laboratory-Confirmed Influenza Detections

In weeks 11 to 15, 1,287 laboratory detections (1,283 influenza A and 4 influenza B) were reported. Detections of influenza have sharply increased, from an average of 40 detections a week in March, to 492 detections in the most recent reporting week.

The threshold for calling the start of a seasonal epidemic in Canada is a 5% positivity rate. With increasing influenza activity, Canada may reach this threshold in the coming weeks and signal the start of a seasonal influenza epidemic.

In weeks 11 to 15, a total of 58,544 tests for influenza were performed at reporting laboratories and the percentage of tests positive for influenza in week 15 was 3.8%. Compared to the past six pre-pandemic seasons (2014-2015 to 2019-2020), an average of 38,685 tests were performed for this time period, with an average of 16% of tests positive for influenza for week 15 (Figure 3).

To date this season (August 29, 2021 to April 16, 2022), 1,842 influenza detections (1,722 influenza A and 120 influenza B) have been reported, which is lower than what we have seen historically in the past six pre-pandemic seasons, where an average of 43,627 influenza detections were reported at this point in the season. Among subtyped influenza A detections (564), influenza A(H3N2) accounted for 97% of detections.

Detailed information on age and type/subtype has been received for 1,566 laboratory-confirmed influenza detections (Figure 4). Among the 1,566 detections, 753 (48%) were in individuals under the 0-19yrs and 468 (30%) were in individuals 20-44yrs.

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 weeks or previous seasons.

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 15: 32 out of 34

Due to different testing protocols of laboratories across Canada, the number of positive tests reported in Figure 2 may not equal the total number of positive tests in the report body text.

Figure 2 - Text description

Surveillance Week	A(Unsubtyped)	A(H3N2)	A(H1N1)	Influenza B	Percent Positive A	Percent Positive B
35	3	0	0	0	0.0	0.0
36	1	0	0	0	0.0	0.0
37	1	2	0	0	0.0	0.0
38	0	0	0	0	0.0	0.0
39	0	0	1	0	0.0	0.0
40	0	0	0	2	0.0	0.0
41	2	1	0	3	0.0	0.0
42	0	1	1	2	0.0	0.0
43	2	1	0	3	0.0	0.0
44	1	2	0	16	0.1	0.1
45	2	8	0	10	0.1	0.1
46	3	8	0	9	0.1	0.1
47	4	5	0	12	0.1	0.1
48	11	6	0	28	0.2	0.2
49	29	6	0	9	0.2	0.1
50	19	6	1	4	0.2	0.0
51	25	12	1	6	0.2	0.0
52	10	10	1	2	0.1	0.0
1	10	9	1	1	0.1	0.0
2	16	2	2	3	0.1	0.0
3	4	2	0	2	0.0	0.0
4	4	2	0	0	0.1	0.0
5	4	1	0	1	0.0	0.0
6	2	1	0	1	0.0	0.0
7	1	1	0	0	0.0	0.0
8	5	1	1	2	0.1	0.0
9	8	4	2	0	0.1	0.0
10	7	8	0	0	0.2	0.0
11	18	9	0	1	0.3	0.0
12	47	35	3	0	0.9	0.0
13	124	103	1	0	1.5	0.0
14	219	149	0	1	2.5	0.0
15	371	154	0	2	3.8	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.

Included in the cumulative detections this season are 11 co-infections of influenza A and B (total of 22 detections) that were suspected to be associated with live attenuated influenza vaccine (LAIV) receipt. Beginning in week 44 co-infections known or reported to be associated with recent LAIV were removed by the submitting laboratory or by the Public Health Agency of Canada as they do not represent community transmission of seasonal influenza viruses.

Figure 3 - Text description

a) Number of influenza tests, 2021-2022 compared to previous seasons

Surveillance Week	Number of Tests, 2021-2022	Number of Tests, 2020-2021	Maximum Number of Tests	Minimum Number of Tests	Average Number of Tests
35	7140	4996	1979	1311	1705
36	8012	5192	2208	1323	1707
37	9316	5335	2631	1778	2135
38	9821	6024	3039	1987	2502
39	9691	6707	3356	2365	2859
40	10776	7127	4078	2443	3134
41	10372	6817	4339	2673	3240
42	12508	6755	4649	2648	3526
43	13341	8227	4996	3084	3862
44	15442	9615	4966	2994	4020
45	17546	10748	5912	3117	4508
46	16418	11955	5589	3176	4564
47	16917	13103	6541	3587	5018
48	18531	18762	7416	3569	5645
49	19974	19649	8559	3836	6377
50	22543	16189	9464	4017	7155
51	28471	14059	11142	3487	8822
52	29555	12290	11338	4272	9184
1	28417	11681	14932	5371	12552
2	23659	14097	16104	5315	13289
3	19585	17002	15001	5270	11820
4	16496	15391	15414	5873	11441
5	15977	16607	16595	6739	11456
6	13873	12949	16121	8324	11339
7	13127	20727	14443	8074	10842
8	12180	21290	14024	7606	10865
9	11282	21891	14520	7507	10956
10	10752	20896	17681	7005	11084
11	10207	21220	12714	6435	9175
12	10808	23087	10431	5976	8238
13	11801	25811	9989	6063	7699
14	12694	26303	8830	4773	7046
15	13034	26284	7836	5090	6527
16	-	26792	6826	5000	5890
17	-	29154	6603	4440	5305
18	-	22152	5640	4143	4780
19	-	12725	5480	3680	4311
20	-	9738	5097	3046	3862
21	-	7442	4001	2577	3197
22	-	6765	3790	2424	2944
23	-	6341	3257	1969	2591
24	-	5942	3120	2034	2449
25	-	5774	2659	1731	2148
26	-	5972	2600	1573	1988
27	-	5213	2163	1554	1833
28	-	4900	2223	1451	1857
29	-	5122	2256	1436	1796
30	-	5275	1950	1463	1664
31	-	5398	2022	1386	1671
32	-	4692	1928	1269	1574
33	-	5616	2089	1251	1671
34	-	5851	2098	1374	1698

b) Percentage of tests positive for influenza, 2021-2022 compared to previous seasons

Surveillance Week	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	0.04	0.02	1.87	0.11	0.82
36	0.01	0.00	2.28	0.30	1.13
37	0.03	0.00	1.78	0.40	0.99
38	0.00	0.02	2.35	0.55	1.30
39	0.01	0.00	2.95	0.67	1.71
40	0.02	0.00	2.33	1.08	1.70
41	0.06	0.01	3.02	1.32	1.72
42	0.05	0.00	3.40	0.87	2.18
43	0.05	0.01	5.32	0.84	2.83
44	0.21	0.07	8.55	1.20	3.70
45	0.13	0.04	10.10	1.39	4.63
46	0.16	0.03	14.11	1.51	6.05
47	0.20	0.07	15.36	1.44	7.71
48	0.35	0.05	18.20	0.84	10.61
49	0.28	0.04	19.71	1.64	13.01
50	0.25	0.01	27.02	2.36	16.82
51	0.20	0.01	29.09	3.30	20.11
52	0.10	0.00	34.54	4.28	24.48
1	0.09	0.00	31.66	5.85	23.41
2	0.12	0.00	29.10	7.06	23.01
3	0.05	0.01	30.07	12.24	23.63
4	0.05	0.00	29.45	15.89	23.96
5	0.04	0.00	30.62	19.60	24.90
6	0.04	0.02	32.39	17.89	25.00
7	0.02	0.01	32.51	16.28	25.05
8	0.07	0.00	32.87	17.45	25.14
9	0.12	0.00	34.28	16.80	24.59
10	0.16	0.00	35.99	16.05	23.22
11	0.28	0.01	31.41	16.19	21.41
12	0.86	0.00	30.03	15.03	20.10
13	1.52	0.00	28.25	14.50	19.56
14	2.47	0.00	23.16	12.66	17.86
15	3.77	0.01	20.73	11.95	16.27
16	-	0.00	18.52	11.64	14.48
17	-	0.00	17.30	9.76	12.83
18	-	0.00	13.02	7.88	10.26
19	-	0.00	11.95	4.96	8.98
20	-	0.01	9.13	3.19	7.22
21	-	0.01	7.45	2.97	5.60
22	-	0.00	4.96	2.19	3.86
23	-	0.00	4.39	0.87	2.86
24	-	0.02	4.36	0.81	2.25
25	-	0.00	3.95	0.63	1.88
26	-	0.00	3.08	0.69	1.81
27	-	0.00	2.83	0.42	1.48
28	-	0.00	1.84	0.41	0.91
29	-	0.00	1.55	0.47	1.09
30	-	0.04	1.46	0.46	0.90
31	-	0.00	1.93	0.58	1.11
32	-	0.00	1.19	0.52	0.92
33	-	0.00	1.69	0.40	0.85
34	-	0.02	1.57	0.42	0.92

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	89.4%	10.6%	269
5 to 19	96.7%	3.3%	437
20 to 44	94.0%	6.0%	440
45 to 64	93.0%	7.0%	133
65+	94.6%	5.4%	191

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	10.7%	89.3%	56
5 to 19	1.6%	98.4%	129
20 to 44	0.6%	99.4%	167
45 to 64	0.0%	100.0%	34
65+	1.5%	98.5%	68

Syndromic / Influenza-like Illness Surveillance

Healthcare Practitioners Sentinel Surveillance

In week 15, 1.2% of visits to healthcare professionals were due to influenza-like illness (ILI). The percentage visits for ILI in weeks 11-15 has increased in recent weeks and are within levels seen pre-pandemic.

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 15: 37

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

FluWatchers

In week 15, 11, 623 participants reported to FluWatchers, of which 1.9% reported symptoms of cough and fever (Figure 6). The percentage of FluWatchers who report cough and fever in weeks 11-15 has been at the highest level seen in the past two seasons and are within levels seen pre-pandemic.

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 225 participants who reported cough and fever:

• 64% consulted a healthcare professional;
• 83% reported days missed from work or school, resulting in a combined total of 190 missed days of work or school (average of 3.3 days);

The Northwest Territories had the highest participation rate this week (53 participants per 100,000 population) and the neighbourhood of K0A had the highest number of participants (144).  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 15: 11, 623

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	2021-2022	2020-2021	Average	Min	Max
35	0.23%	0.22%	N/A	N/A	N/A
36	0.28%	0.21%	N/A	N/A	N/A
37	0.49%	0.38%	N/A	N/A	N/A
38	0.54%	0.29%	N/A	N/A	N/A
39	0.54%	0.45%	N/A	N/A	N/A
40	0.58%	0.49%	2.51%	2.18%	2.71%
41	0.46%	0.44%	2.18%	1.81%	2.57%
42	0.38%	0.33%	1.80%	1.61%	2.03%
43	0.53%	0.17%	1.87%	1.49%	2.18%
44	0.51%	0.26%	1.57%	1.39%	1.78%
45	0.54%	0.29%	1.83%	1.42%	2.32%
46	0.41%	0.28%	1.83%	1.22%	2.15%
47	0.57%	0.31%	1.93%	1.44%	2.39%
48	0.51%	0.26%	2.43%	1.67%	3.35%
49	0.40%	0.17%	2.56%	1.97%	3.16%
50	0.60%	0.15%	2.91%	2.12%	3.79%
51	1.03%	0.22%	3.18%	2.53%	3.95%
52	1.51%	0.10%	3.98%	2.81%	5.38%
1	1.08%	0.12%	3.84%	2.85%	4.76%
2	0.99%	0.21%	2.94%	1.90%	3.93%
3	0.77%	0.12%	3.25%	2.35%	4.84%
4	0.56%	0.12%	3.12%	2.13%	4.23%
5	0.64%	0.17%	3.19%	2.62%	3.59%
6	0.51%	0.11%	3.47%	2.76%	4.28%
7	0.43%	0.16%	3.18%	2.58%	3.79%
8	0.49%	0.06%	3.09%	2.54%	3.65%
9	0.45%	0.10%	2.81%	2.38%	3.53%
10	0.64%	0.18%	2.58%	2.12%	3.11%
11	0.88%	0.16%	2.33%	1.89%	2.63%
12	1.16%	0.17%	2.60%	2.46%	2.82%
13	1.79%	0.17%	2.48%	1.99%	3.06%
14	2.26%	0.19%	2.13%	1.35%	2.58%
15	1.94%	0.21%	1.78%	1.60%	1.93%
16	-	0.14%	2.00%	1.47%	2.44%
17	-	0.22%	1.73%	1.40%	2.31%
18	-	0.15%	1.50%	1.19%	2.09%
19	-	0.14%	N/A	N/A	N/A
20	-	0.15%	N/A	N/A	N/A
21	-	0.09%	N/A	N/A	N/A
22	-	0.10%	N/A	N/A	N/A
23	-	0.08%	N/A	N/A	N/A
24	-	0.13%	N/A	N/A	N/A
25	-	0.12%	N/A	N/A	N/A
26	-	0.16%	N/A	N/A	N/A
27	-	0.11%	N/A	N/A	N/A
28	-	0.20%	N/A	N/A	N/A
29	-	0.20%	N/A	N/A	N/A
30	-	0.22%	N/A	N/A	N/A
31	-	0.21%	N/A	N/A	N/A
32	-	0.25%	N/A	N/A	N/A
33	-	0.31%	N/A	N/A	N/A
34	-	0.50%	N/A	N/A	N/A

Influenza Outbreak Surveillance

In week 15, two outbreaks were reported (one in a long-term care facility and one in a facility categorized as ‘other’, which can include facilities such as private personal care homes, correctional facilities, and colleges/universities).

To date this season (August 29, 2021 to April 16, 2022), 12 laboratory-confirmed influenza outbreaks and 55 ILI outbreaks have been reported. Among the 12 laboratory-confirmed influenza outbreaks, six were in long-term care facilities, 5 in facilities categorized as ‘other’ and one in an acute care facility.  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. For more information on the respiratory viruses currently circulating in Canada, please refer to the Respiratory Virus Detections in Canada.

Number of provinces and territories^{Footnote 1} reporting in week 15: 11 out of 13

Influenza Severe Outcomes Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 15, 14 influenza-associated hospitalizations and less than five ICU admissions were reported by participating provinces and territories^{Footnote 2}.

To date this season (August 29, 2021 to April 16, 2022), 43 influenza-associated hospitalizations and less than five ICU admissions were reported by participating provinces and territories. All but one hospitalization was due to influenza A and 20 (47%) were in adults 65 years of age and older.

Number of provinces and territories reporting in week 15: 7 out of 9

Pediatric Influenza Hospitalizations and Deaths

In week 15, 19 influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. There has been in sharp increase in influenza-associated pediatric hospitalizations in recent weeks.

To date this season (August 29, 2021 to April 16, 2022), 40 pediatric influenza-associated hospitalizations have been reported, of which 25 (63%) were among children under the age of 5 years of age. Less than five intensive care unit (ICU) admissions have been reported.

Adult Influenza Hospitalizations and Deaths

In week 15, less than five influenza-associated adult (≥16 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) network.
To date this season (August 29, 2021 to April 16, 2022), five influenza-associated adult (≥16 years of age) hospitalizations have been reported by the CIRN SOS network.

Influenza Strain Characterization

To date this season (August 29, 2021 to April 16, 2022), the National Microbiology Laboratory (NML) has characterized 47 influenza viruses (45 A(H3N2), 2 A(H1N1)) received from Canadian laboratories.

Influenza A(H3N2)

Genetic Characterization

Among the 45 influenza A(H3N2) viruses genetically characterized, sequence analysis of the HA gene of these viruses showed that they all belonged to genetic group 3C.2a1b.2a2.

A/Cambodia/e0826360/2020 (H3N2)-like virus is the influenza A(H3N2) component of the 2021-2022 Northern Hemisphere seasonal influenza vaccine and belongs to genetic group 3C.2a1b.2a1.

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

Antigenic Characterization

Among the 45 A(H3N2) viruses characterized:

• 8 viruses were antigenically similar to A/Cambodia/e0826360/2020 (H3N2)-like virus
• 37 showed reduced titers with antisera raised against egg-grown A/Cambodia/e0826360/2020 (H3N2)-like virus.

Influenza A(H1N1)

Antigenic Characterization

Among the two A(H1N1) viruses characterized:

• One H1N1 virus characterized was antigenically similar to A/Wisconsin/588/2019.
• One H1N1 showed reduced titer with ferret antisera raised against cell culture-propagated A/Wisconsin/588/2019

A/Wisconsin/588/2019 is the influenza A(H1N1) component of the 2021-2022 Northern Hemisphere seasonal influenza vaccine.

Antiviral Resistance

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

Oseltamivir

47 influenza viruses (45 A(H3N2) and 2 A(H1N1)) were tested for resistance to oseltamivir:

• All influenza viruses were sensitive to oseltamivir.

Zanamivir

47 influenza viruses (45 A(H3N2) and 2 A(H1N1)) were tested for resistance to zanamivir:

• 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

The Seasonal Influenza Immunization 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. Vaccine coverage is measured as the percentage of people who reported receiving the influenza vaccine in a specific influenza season.
In the 2021-22 influenza season, coverage was similar to the 2020-21 season at:

• 30% among adults aged 18 to 64 years.
  • 27% among adults aged 18-64 without chronic medical conditions.
  • 38% among adults aged 18-64 with chronic medical conditions.
• 71% among seniors (aged 65 years and older).

Table 1 – Influenza vaccine coverage among adults (n=3,502)^{Footnote *} by risk group^{Footnote †} and gender^{Footnote ‡}, Seasonal Influenza Vaccination Coverage Survey, Canada, September 2021 – February 2022

Age group (years)	All		Male		Female
	N	Vaccine Coverage % (95% CI)	N	Vaccine Coverage % (95% CI)	N	Vaccine Coverage % (95% CI)
All adults (≥18)	3487	38.7 (36.9-40.6)	1548	33.4 (30.8-36.0)	1914	43.9 (41.3-46.5)
18-64	2389	30.1 (28.0-32.2)	1079	24.9 (22.1-27.8)	1286	35.0 (31.9-38.1)
with chronic medical conditions	713	37.6 (33.6-41.7)	298	37.0 (31.0-43.1)	407	38.3 (32.9-43.8)
without chronic medical conditions	1658	26.8 (24.4-29.2)	769	19.9 (16.9-23.0)	873	33.7 (29.9-37.4)
≥65	1098	71.0 (68.1-74.0)	469	67.0 (62.2-71.8)	628	74.6 (70.9-78.3)
Table 1 Note * 18 people did not recall whether they had received the influenza vaccine and were excluded from coverage estimates. Return to table 1 note * referrer Table 1 Note † 11 people who were 18-64 years old did not disclose whether they had any chronic medical conditions (CMC) and were excluded from stratified analysis. Return to table 1 note † referrer Table 1 Note ‡ 11 people did not disclose their gender and 9 people did not identify as male or female. They were excluded from stratified analysis. Return to table 1 note ‡ referrer

Vaccine Effectiveness

Within season influenza vaccine effectiveness (VE) estimates are typically available in February or March of each year. Given the low influenza circulation this season to date, VE estimates will not be available for the 2021-2022 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.