FluWatch report: April 25 to May 22, 2021 (weeks 17-20)

Influenza/influenza-like illness (ILI) activity (geographic spread)

During week 20, one region reported sporadic influenza/ILI activity. All other regions reported no activity (Figure 1).

Figure 1 - Text equivalent

Province	Influenza Surveillance Region	Activity Level
N.L.	Eastern	No Activity
N.L.	Labrador-Grenfell	No Data
N.L.	Central	No Data
N.L.	Western	No Data
P.E.I.	Prince Edward Island	No Activity
N.S.	Zone 1 - Western	No Data
N.S.	Zone 2 - Northern	No Activity
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	No Activity
N.B.	Region 5	No Activity
N.B.	Region 6	No Activity
N.B.	Region 7	No Activity
Que.	Nord-est	No Activity
Que.	Québec et Chaudieres-Appalaches	No Activity
Que.	Centre-du-Québec	No Activity
Que.	Montréal et Laval	No Activity
Que.	Ouest-du-Québec	No Activity
Que.	Montérégie	No Activity
Ont.	Central East	No Activity
Ont.	Central West	No Activity
Ont.	Eastern	No Activity
Ont.	North East	No Activity
Ont.	North West	No Activity
Ont.	South West	No Activity
Ont.	Toronto	No Activity
Man.	Northern Regional	No Activity
Man.	Prairie Mountain	Sporadic
Man.	Interlake-Eastern	No Activity
Man.	Winnipeg	No Activity
Man.	Southern Health	No Activity
Sask.	North	No Activity
Sask.	Central	No Activity
Sask.	South	No Activity
Alta.	North Zone	No Activity
Alta.	Edmonton	No Activity
Alta.	Central Zone	No Activity
Alta.	Calgary	No Activity
Alta.	South Zone	No Activity
B.C.	Interior	No Activity
B.C.	Fraser	No Activity
B.C.	Vancouver Coastal	No Activity
B.C.	Vancouver Island	No Activity
B.C.	Northern	No Activity
Y.T.	Yukon	No Activity
N.W.T.	North	No Activity
N.W.T.	South	No Activity
Nvt.	Qikiqtaaluk	No Activity
Nvt.	Kivalliq	No Activity
Nvt.	Kitimeot	No Activity

Laboratory-confirmed influenza detections

In weeks 17 to 20, four laboratory detections of influenza were reported.

To date this season, 72 influenza detections have been reported (Figure 2), which is significantly lower than the past six seasons where an average of 51,508 influenza detections were reported for the season to date. All provinces and territories are closely monitoring indicators of influenza activity this season. Data in the FluWatch report represent surveillance data available at the time of writing, and may change as updates are received.

Thirty-one of the influenza detections reported to date this season are known to be associated with recent live attenuated influenza vaccine (LAIV) receipt and do not represent community circulation of seasonal influenza viruses. LAIV strains are attenuated but can be recovered by nasal swab in children and adults following vaccination with that product (i.e., "shedding"). For more information, please refer to the Canadian Immunization Guide Chapter on Influenza and Statement on Seasonal Influenza Vaccine for 2020–2021 (Section IV.2)

Overall, the percentage of laboratory tests positive for influenza remains at exceptionally low levels, despite the elevated levels of testing seen this week. In weeks 17 to 20, 52,015 tests for influenza were performed at reporting laboratories and the average percentage of tests positive was 0%. Compared to the past six seasons, the number of tests performed for this time period was higher than the average (18,257) and the percentage of tests positive for influenza remains well below average (9.8%) (Figure 3a and 3b).

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 Figure 2 or the Respiratory Virus Detections in Canada Report.

Number of laboratories reporting in week 20: 33 out of 35

The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the period of seasonal influenza activity.

Figure 2 - Text equivalent

Surveillance Week	A(Unsubtyped)	A(H3N2)	A(H1N1)	Influenza B	Percent Positive A	Percent Positive B
35	0	0	0	1	0.0	0.0
36	0	0	0	0	0.0	0.0
37	0	0	0	0	0.0	0.0
38	1	0	0	0	0.0	0.0
39	0	0	0	0	0.0	0.0
40	0	0	0	0	0.0	0.0
41	1	0	0	0	0.0	0.0
42	0	0	0	0	0.0	0.0
43	1	0	0	0	0.0	0.0
44	2	2	1	3	0.0	0.0
45	2	0	0	2	0.0	0.0
46	3	0	0	1	0.0	0.0
47	3	1	1	5	0.0	0.0
48	6	2	0	2	0.0	0.0
49	2	1	3	2	0.0	0.0
50	1	0	0	1	0.0	0.0
51	1	0	0	1	0.0	0.0
52	0	0	0	0	0.0	0.0
53	0	0	2	0	0.0	0.0
1	0	0	0	0	0.0	0.0
2	1	1	2	1	0.0	0.0
3	0	0	0	0	0.0	0.0
4	0	0	0	0	0.0	0.0
5	1	0	1	0	0.0	0.0
6	2	1	0	1	0.0	0.0
7	1	0	0	1	0.0	0.0
8	0	0	0	0	0.0	0.0
9	0	0	0	0	0.0	0.0
10	2	0	0	0	0.0	0.0
11	0	0	0	0	0.0	0.0
12	0	0	0	0	0.0	0.0
13	0	0	0	0	0.0	0.0
14	2	0	0	0	0.0	0.0
15	0	0	0	0	0.0	0.0
16	0	0	0	0	0.0	0.0
17	1	0	0	0	0.0	0.0
18	0	0	0	0	0.0	0.0
19	0	0	1	1	0.0	0.0
20	1	0	0	0	0.0	0.0

The shaded area represents the maximum and minimum number of influenza tests (a) or percentage of tests positive (b) reported by week from seasons 2014-2015 to 2019-2020.

Figure 3 - Text equivalent

a) Current number of influenza tests performed, compared to previous seasons

Surveillance Week	Number of Tests, 2020-21	Maximum Number of Tests	Minimum Number of Tests	Average Number of Tests
35	4996	1979	1311	1705
36	5192	2208	1323	1707
37	5335	2631	1778	2135
38	6024	3039	1987	2502
39	6707	3356	2365	2859
40	7127	4078	2443	3134
41	6817	4339	2673	3240
42	6755	4649	2648	3526
43	8227	4996	3084	3862
44	9615	4966	2994	4020
45	10748	5912	3117	4508
46	11955	5589	3176	4564
47	13103	6541	3587	5018
48	18762	7416	3569	5645
49	19649	8559	3836	6377
50	16189	9464	4017	7155
51	14059	11142	3487	8822
52	12290	11338	4272	9184
53	11681	13135	4821.5	10868
1	14097	14932	5371	12552
2	17002	16104	5315	13289
3	15391	15001	5270	11820
4	16607	15414	5873	11441
5	12914	16595	6739	11456
6	20715	16121	8324	11339
7	21255	14443	8074	10842
8	20971	14024	7606	10865
9	20896	14520	7507	10956
10	21220	17681	7005	11084
11	23087	12714	6435	9175
12	25811	10431	5976	8238
13	26286	9989	6063	7699
14	26279	8830	4773	7046
15	26789	7836	5090	6527
16	29154	6826	5000	5890
17	22152	6603	4440	5305
18	02725	5640	4143	4780
19	9738	5480	3680	4311
20	7400	5097	3046	3862
21	#N/A	4001	2577	3197
22	#N/A	3790	2424	2944
23	#N/A	3257	1969	2591
24	#N/A	3120	2034	2449
25	#N/A	2659	1731	2148
26	#N/A	2600	1573	1988
27	#N/A	2163	1554	1833
28	#N/A	2223	1451	1857
29	#N/A	2256	1436	1796
30	#N/A	1950	1463	1664
31	#N/A	2022	1386	1671
32	#N/A	1928	1269	1574
33	#N/A	2089	1251	1671
34	#N/A	2098	1374	1698

b) Current percentage of tests positive for influenza, compared to previous seasons

Surveillance Week	Percentage of tests positive, 2020-21	Maximum Percentage of Tests Positive	Minimum Percentage of Tests Positive	Average Percentage of Tests Positive
35	0.02	1.87	0.11	0.82
36	0.00	2.28	0.30	1.13
37	0.00	1.78	0.40	0.99
38	0.02	2.35	0.55	1.30
39	0.00	2.95	0.67	1.71
40	0.00	2.33	1.08	1.70
41	0.01	3.02	1.32	1.72
42	0.00	3.40	0.87	2.18
43	0.01	5.32	0.84	2.83
44	0.07	8.55	1.20	3.70
45	0.04	10.10	1.39	4.63
46	0.03	14.11	1.51	6.05
47	0.07	15.36	1.44	7.71
48	0.05	18.20	0.84	10.61
49	0.04	19.71	1.64	13.01
50	0.01	27.02	2.36	16.82
51	0.01	29.09	3.30	20.11
52	0.00	34.54	4.28	24.48
53	0.02	33.10	5.06	23.95
1	0.00	31.66	5.85	23.41
2	0.03	29.10	7.06	23.01
3	0.00	30.07	12.24	23.63
4	0.00	29.45	15.89	23.96
5	0.02	30.62	19.60	24.90
6	0.02	32.39	17.89	25.00
7	0.01	32.51	16.28	25.05
8	0.00	32.87	17.45	25.14
9	0.00	34.28	16.80	24.59
10	0.01	35.99	16.05	23.22
11	0.00	31.41	16.19	24.41
12	0.00	30.03	15.03	20.10
13	0.00	28.25	14.50	19.56
14	0.01	23.16	12.66	17.86
15	0.00	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	0.02	11.95	4.96	8.98
20	0.01	9.13	3.19	7.22
21	#N/A	7.45	2.97	5.60
22	#N/A	4.96	2.19	3.86
23	#N/A	4.39	0.87	2.86
24	#N/A	4.36	0.81	2.25
25	#N/A	3.95	0.63	1.88
26	#N/A	3.08	0.69	1.81
27	#N/A	2.83	0.42	1.48
28	#N/A	1.84	0.41	0.91
29	#N/A	1.55	0.47	1.09
30	#N/A	1.46	0.46	0.90
31	#N/A	1.93	0.58	1.11
32	#N/A	1.19	0.52	0.92
33	#N/A	1.69	0.40	0.85
34	#N/A	1.57	0.42	0.92

Syndromic / influenza-like illness surveillance

Healthcare practitioners sentinel syndromic surveillance

In weeks 17 to 20, an average of 0.4% of visits to healthcare professionals were due to influenza-like illness (ILI), which remains lower than average compared to recent seasons (Figure 4).

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

Number of Sentinels Reporting in Week 20: 54

The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2014-2015 to 2019-2020

Figure 4 - Text equivalent

Surveillance Week	2020-2021	Average	Min	Max
35	0.1%	0.6%	0.4%	0.9%
36	0.2%	0.7%	0.4%	1.0%
37	0.4%	0.7%	0.6%	1.0%
38	0.3%	0.9%	0.5%	1.2%
39	0.4%	1.1%	0.8%	1.7%
40	0.2%	1.6%	0.8%	2.8%
41	0.4%	1.5%	0.9%	2.1%
42	0.5%	1.2%	0.8%	1.7%
43	0.3%	1.1%	0.7%	1.7%
44	0.3%	1.1%	0.9%	1.5%
45	0.4%	1.3%	0.7%	1.8%
46	0.8%	1.5%	1.1%	2.2%
47	0.3%	1.4%	1.1%	2.2%
48	0.5%	1.5%	0.9%	2.8%
49	0.5%	1.4%	1.0%	1.7%
50	0.4%	1.8%	1.4%	2.7%
51	0.5%	1.8%	1.0%	3.1%
52	0.5%	3.3%	1.9%	5.4%
53	0.7%	3.3%	1.9%	5.5%
1	0.4%	3.3%	1.8%	5.7%
2	0.2%	2.2%	1.3%	3.7%
3	0.3%	1.9%	1.1%	2.9%
4	0.2%	2.0%	1.4%	3.1%
5	0.5%	2.3%	1.4%	4.0%
6	0.3%	2.3%	0.9%	3.5%
7	0.2%	2.1%	0.8%	3.4%
8	0.2%	2.1%	0.9%	3.1%
9	0.2%	1.9%	1.0%	2.8%
10	0.2%	1.8%	1.1%	2.8%
11	0.3%	1.6%	0.6%	2.6%
12	0.4%	1.6%	1.1%	2.6%
13	0.2%	1.7%	1.1%	3.0%
14	0.3%	1.3%	0.9%	1.9%
15	0.3%	1.2%	0.8%	1.7%
16	0.4%	1.2%	0.7%	1.7%
17	0.5%	1.3%	0.5%	2.0%
18	0.3%	0.9%	0.6%	1.3%
19	0.5%	1.1%	0.6%	1.5%
20	0.3%	0.9%	0.5%	1.3%
21	#N/A	0.7%	0.3%	1.0%
22	#N/A	0.8%	0.6%	1.0%
23	#N/A	0.7%	0.6%	1.0%
24	#N/A	0.6%	0.4%	0.8%
25	#N/A	0.8%	0.5%	1.4%
26	#N/A	0.6%	0.5%	0.7%
27	#N/A	0.7%	0.5%	1.3%
28	#N/A	0.9%	0.6%	1.7%
29	#N/A	0.6%	0.2%	0.9%
30	#N/A	0.4%	0.2%	0.6%
31	#N/A	0.8%	0.3%	1.2%
32	#N/A	0.7%	0.4%	1.3%
33	#N/A	0.7%	0.4%	1.5%
34	#N/A	0.6%	0.4%	0.9%

FluWatchers

In week 20, 12,343 participants reported to FluWatchers, and a total of 9 participants (0.07%) reported symptoms of cough and fever (Figure 5). The percentage of participants reporting cough and fever remains at very low levels and may be a direct effect of individual and public health measures enacted to reduce the spread of COVID-19. FluWatchers reporting is not impacted by changes in health services or health seeking behaviours.

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

Number of Participants Reporting in Week 20: 12,343

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

Figure 5 - Text equivalent

Surveillance Week	2020-2021	Average	Min	Max
35	0.22%	N/A	N/A	N/A
36	0.21%	N/A	N/A	N/A
37	0.38%	N/A	N/A	N/A
38	0.29%	N/A	N/A	N/A
39	0.45%	N/A	N/A	N/A
40	0.49%	2.51%	2.18%	2.71%
41	0.44%	2.18%	1.81%	2.57%
42	0.33%	1.80%	1.61%	2.03%
43	0.17%	1.87%	1.49%	2.18%
44	0.26%	1.57%	1.39%	1.78%
45	0.29%	1.83%	1.42%	2.32%
46	0.28%	1.83%	1.22%	2.15%
47	0.31%	1.93%	1.44%	2.39%
48	0.26%	2.43%	1.67%	3.35%
49	0.17%	2.56%	1.97%	3.16%
50	0.15%	2.91%	2.12%	3.79%
51	0.22%	3.18%	2.53%	3.95%
52	0.10%	3.98%	2.81%	5.38%
53	0.12%	3.91%	2.83%	5.07%
1	0.21%	3.84%	2.85%	4.76%
2	0.12%	2.94%	1.90%	3.93%
3	0.12%	3.25%	2.35%	4.84%
4	0.17%	3.12%	2.13%	4.23%
5	0.11%	3.19%	2.62%	3.59%
6	0.16%	3.47%	2.76%	4.28%
7	0.06%	3.18%	2.58%	3.79%
8	0.10%	3.09%	2.54%	3.65%
9	0.18%	2.81%	2.38%	3.53%
10	0.16%	2.58%	2.12%	3.11%
11	0.17%	2.33%	1.89%	2.63%
12	0.17%	2.60%	2.46%	2.82%
13	0.19%	2.48%	1.99%	3.06%
14	0.21%	2.13%	1.35%	2.58%
15	0.14%	1.78%	1.60%	1.93%
16	0.22%	2.00%	1.47%	2.44%
17	0.15%	1.73%	1.40%	2.31%
18	0.14%	1.50%	1.19%	2.09%
19	0.15%	N/A	N/A	N/A
20	0.07%	N/A	N/A	N/A
21		N/A	N/A	N/A
22		N/A	N/A	N/A
23		N/A	N/A	N/A
24		N/A	N/A	N/A
25		N/A	N/A	N/A
26		N/A	N/A	N/A
27		N/A	N/A	N/A
28		N/A	N/A	N/A
29		N/A	N/A	N/A
30		N/A	N/A	N/A
31		N/A	N/A	N/A
32		N/A	N/A	N/A
33		N/A	N/A	N/A
34		N/A	N/A	N/A

Click on the map to access the link

Influenza outbreak surveillance

In weeks 17 to 20, two influenza-like-illness (ILI) outbreaks in schools and/or daycares were reported.

To date this season, 130 influenza-like-illness (ILI) outbreaks in schools and/or daycares, and no other influenza or ILI outbreaks have been reported in any other settings.

Outbreaks of ILI in schools and daycares are identified when greater than 10% absenteeism due to ILI are reported in these settings. The number of ILI outbreaks in schools and daycares reported is higher compared to the same time period in the previous two seasons. This is not unexpected given changes to outbreak surveillance, specifically increased vigilance in schools to monitor and report absenteeism due to ILI, and the increased restrictions on attendance for children with symptoms of viral respiratory illness.

Outbreaks of ILI are not specific to any one respiratory pathogen and can be due influenza or other respiratory viruses, including rhinovirus and SARS-CoV-2, the virus that causes COVID-19. For more information on the respiratory viruses currently circulating in Canada, please refer to the Respiratory Virus Detections in Canada Report.

Number of provinces and territories reporting in weeks 17 to 20^{Footnote 1}: 11 out of 13

Severe outcomes influenza surveillance

Provincial/territorial influenza hospitalizations and deaths

In weeks 17 to 20, no influenza-associated hospitalizations were reported by participating provinces and territories^{Footnote 2}. To date this season no influenza-associated hospitalizations were reported by participating provinces and territories.

Number of provinces and territories reporting in weeks 17 to 20: 7 out of 9

Pediatric influenza hospitalization and deaths

In weeks 17 to 20 no influenza-associated hospitalizations were reported. To date this season, less than five pediatric (≤16 years of age) hospitalizations with influenza have been reported by the Immunization Monitoring Program Active (IMPACT) network.

Adult influenza hospitalization and deaths

Surveillance of laboratory-confirmed influenza-associated adult (≥16 years of age) hospitalizations by the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) network has not yet begun for the 2020-2021 season.

Influenza strain characterizations

Due to the very low influenza circulation to date this season, the National Microbiology Laboratory has not received influenza viruses collected during the 2020-2021 season for strain characterization.

Antiviral resistance

Due to the very low influenza circulation to date this season, the National Microbiology Laboratory has not received influenza viruses collected during the 2020-2021 season for antiviral resistance testing.

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 2020-21 influenza season, coverage was similar to the 2019-20 season, at:

• 32% among adults aged 18 to 64 years.
  • 29% among adults aged 18-64 without chronic medical conditions.
  • 41% among adults aged 18 to 64 years with chronic medical conditions.
• 70% among seniors (aged 65 years and older).

Table 1 – Influenza vaccine coverage among adults (n=3,032)^{Footnote *} by risk group^{Footnote †} and gender^{Footnote ‡},
Seasonal Influenza Vaccination Coverage Survey, Canada, 2020-2021

Age group (years)	All		Male		Female
	N	Vaccine Coverage % (95% CI)	N	Vaccine Coverage % (95% CI)	N	Vaccine Coverage % (95% CI)
All adults (≥18)	3014	40.4 (38.4-42.4)	1399	35.2 (32.5-38.0)	1595	45.2 (42.4-48.1)
18-64	2152	32.4 (30.1-34.6)	1024	27.3 (24.3-30.3)	1115	37.4 (34.1-40.7)
-  with chronic medical conditions	646	40.5 (36.2-44.8)	286	36.9 (30.7-43.1)	354	43.5 (37.5-49.4)
-  without chronic medical conditions	1498	29.2 (26.6-31.8)	734	24.2 (20.8-27.6)	757	34.6 (30.6-38.5)
≥65	862	70.4 (67.1-73.8)	375	68.0 (62.8-73.2)	480	72.8 (68.4-77.1)
Footnote * 18 people did not recall whether they had received the influenza vaccine and were excluded from coverage estimates. Return to footnote * referrer Footnote † 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 footnote † referrer Footnote ‡ 11 people did not disclose their gender and 9 people did not identify themselves as male or female. They were excluded from stratified analysis. Return to footnote ‡ referrer

Vaccine effectiveness

Influenza vaccine effectiveness 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 2020-2021 season.

Notes

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