FluWatch report: November 7 to November 13, 2021 (week 45)

Organization: Public Health Agency of Canada

Published: 2021-11-19

Related Topics

• Flu (influenza)
• Influenza surveillance

Weekly Highlights

• In week 45, influenza activity across Canada was low with 85% of regions reporting no influenza activity. In the past week, all influenza indicators were at low interseasonal levels. 

Virologic

• In week 45, a total of 22 influenza detections (12 influenza A and 10 influenza B) were reported.
• Among the 12 detections with detailed age information, all were individuals under the age of 44 years.

Syndromic

• The percentage visits for influenza-like illness (ILI) was 2.15% in week 45.
• The percentage of FluWatchers reporting fever and cough was 0.55% in week 45; it remains below expected levels and is stable.

Outbreaks

• In week 45, no outbreaks were reported.
• From August 29 to November 13, 2021 (weeks 35 to 45), 11 ILI outbreaks and no laboratory-confirmed influenza outbreaks have been reported.

Severe Outcomes

• From August 29 to November 13, 2021 (weeks 35 to 45), no influenza-associated hospitalizations have been reported from participating provinces and territories.

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 45, eight regions in four provinces (B.C., Alta., Ont., and Que.) reported sporadic influenza/ILI activity. All other surveillance regions reported no influenza/ILI activity (Figure 1).

Number of Regions Reporting in Week 45: 53 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	No Activity
P.E.I.	Prince Edward Island	No Activity
N.S.	Zone 1 - Western	No Activity
N.S.	Zone 2 - Northern	No Activity
N.S.	Zone 3 - Eastern	No Activity
N.S.	Zone 4 - Central	No Activity
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	Sporadic
Que.	Ouest-du-Québec	No Activity
Que.	Montérégie	No Activity
Ont.	Central East	Sporadic
Ont.	Central West	Sporadic
Ont.	Eastern	No Activity
Ont.	North East	No Activity
Ont.	North West	No Activity
Ont.	South West	No Activity
Ont.	Toronto	Sporadic
Man.	Northern Regional	No Activity
Man.	Prairie Mountain	No Activity
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	Sporadic
Alta.	Central Zone	No Activity
Alta.	Calgary	No Activity
Alta.	South Zone	No Activity
B.C.	Interior	Sporadic
B.C.	Fraser	Sporadic
B.C.	Vancouver Coastal	Sporadic
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 week 45, 22 laboratory detections of influenza were reported (12 influenza A and 10 influenza B). An additional 14 influenza detections were known to be associated with recent live attenuated influenza vaccine (LAIV) receipt and were excluded from the data as they do not represent community transmission 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, refer to the Canadian Immunization Guide Chapter on Influenza and Statement on Seasonal Influenza Vaccine for 2021–2022 (Section IV.2).

Overall, the percentage of laboratory tests positive for influenza remains at exceptionally low levels, despite the elevated levels of testing. In week 45, 16,630 tests for influenza were performed at reporting laboratories and the percentage of tests positive for influenza was 0.13%. Compared to the past six pre-pandemic seasons (2014-2015 to 2019-2020), an average of 4,508 tests were performed for this time period, with an average of 4.6% of tests positive for influenza (Figure 3).

To date this season (August 28 to November 13, 2021), 89 influenza detections (50 influenza A and 39 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 818 influenza detections were reported at this point in the season. Excluded from these 89 influenza detections were 16 detections known to be associated LAIV receipt as they do not represent community transmission of seasonal influenza viruses, and 22 were suspected to be associated with recent LAIV receipt but were retained pending confirmation. Among subtyped influenza A detections (12), influenza A(H3N2) accounted for 83% of detections.

Detailed information on age and type/subtype has been received for 54 laboratory-confirmed influenza detections. Among the 54 detections, all were in individuals under the age of 65 (Figure 4).

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 45: 31 out of 34

For one province, only data from subtyped influenza A specimens are included in the weekly number of positive influenza tests in Figure 2. The number of positive tests reported in Figure 2 may not equal the total number of positive tests in the report body text.

Influenza detections known to be associated with recent LAIV receipt (N=16) are excluded from Figure 2 as they do not represent community transmission of seasonal influenza viruses.

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	3	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	1	1	1	2	0.0	0.0
43	2	1	0	3	0.0	0.0
44	1	1	0	19	0.1	0.1
45	0	0	0	0	0.0	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.

Figure 3 - Text description

a) Number of influenza tests, 2020-2021 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	6896	4996	1979	1311	1705
36	7686	5192	2208	1323	1707
37	8903	5335	2631	1778	2135
38	9353	6024	3039	1987	2502
39	9370	6707	3356	2365	2859
40	10493	7127	4078	2443	3134
41	10079	6817	4339	2673	3240
42	12275	6755	4649	2648	3526
43	12908	8227	4996	3084	3862
44	14810	9615	4966	2994	4020
45	16630	10748	5912	3117	4508
46	N/A	11955	5589	3176	4564
47	N/A	13103	6541	3587	5018
48	N/A	18762	7416	3569	5645
49	N/A	19649	8559	3836	6377
50	N/A	16189	9464	4017	7155
51	N/A	14059	11142	3487	8822
52	N/A	12290	11338	4272	9184
1	N/A	11681	14932	5371	12552
2	N/A	14097	16104	5315	13289
3	N/A	17002	15001	5270	11820
4	N/A	15391	15414	5873	11441
5	N/A	16607	16595	6739	11456
6	N/A	12949	16121	8324	11339
7	N/A	20727	14443	8074	10842
8	N/A	21290	14024	7606	10865
9	N/A	21891	14520	7507	10956
10	N/A	20896	17681	7005	11084
11	N/A	21220	12714	6435	9175
12	N/A	23087	10431	5976	8238
13	N/A	25811	9989	6063	7699
14	N/A	26303	8830	4773	7046
15	N/A	26284	7836	5090	6527
16	N/A	26792	6826	5000	5890
17	N/A	29154	6603	4440	5305
18	N/A	22152	5640	4143	4780
19	N/A	12725	5480	3680	4311
20	N/A	9738	5097	3046	3862
21	N/A	7442	4001	2577	3197
22	N/A	6765	3790	2424	2944
23	N/A	6341	3257	1969	2591
24	N/A	5942	3120	2034	2449
25	N/A	5774	2659	1731	2148
26	N/A	5972	2600	1573	1988
27	N/A	5213	2163	1554	1833
28	N/A	4900	2223	1451	1857
29	N/A	5122	2256	1436	1796
30	N/A	5275	1950	1463	1664
31	N/A	5398	2022	1386	1671
32	N/A	4692	1928	1269	1574
33	N/A	5616	2089	1251	1671
34	N/A	5851	2098	1374	1698

b) Percentage of tests positive for influenza, 2020-2021 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	0.04	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	0.25	0.07	8.55	1.20	3.70
45	0.13	0.04	10.10	1.39	4.63
46	N/A	0.03	14.11	1.51	6.05
47	N/A	0.07	15.36	1.44	7.71
48	N/A	0.05	18.20	0.84	10.61
49	N/A	0.04	19.71	1.64	13.01
50	N/A	0.01	27.02	2.36	16.82
51	N/A	0.01	29.09	3.30	20.11
52	N/A	0.00	34.54	4.28	24.48
1	N/A	0.00	31.66	5.85	23.41
2	N/A	0.00	29.10	7.06	23.01
3	N/A	0.01	30.07	12.24	23.63
4	N/A	0.00	29.45	15.89	23.96
5	N/A	0.00	30.62	19.60	24.90
6	N/A	0.02	32.39	17.89	25.00
7	N/A	0.01	32.51	16.28	25.05
8	N/A	0.00	32.87	17.45	25.14
9	N/A	0.00	34.28	16.80	24.59
10	N/A	0.00	35.99	16.05	23.22
11	N/A	0.01	31.41	16.19	21.41
12	N/A	0.00	30.03	15.03	20.10
13	N/A	0.00	28.25	14.50	19.56
14	N/A	0.00	23.16	12.66	17.86
15	N/A	0.01	20.73	11.95	16.27
16	N/A	0.00	18.52	11.64	14.48
17	N/A	0.00	17.30	9.76	12.83
18	N/A	0.00	13.02	7.88	10.26
19	N/A	0.00	11.95	4.96	8.98
20	N/A	0.01	9.13	3.19	7.22
21	N/A	0.01	7.45	2.97	5.60
22	N/A	0.00	4.96	2.19	3.86
23	N/A	0.00	4.39	0.87	2.86
24	N/A	0.02	4.36	0.81	2.25
25	N/A	0.00	3.95	0.63	1.88
26	N/A	0.00	3.08	0.69	1.81
27	N/A	0.00	2.83	0.42	1.48
28	N/A	0.00	1.84	0.41	0.91
29	N/A	0.00	1.55	0.47	1.09
30	N/A	0.04	1.46	0.46	0.90
31	N/A	0.00	1.93	0.58	1.11
32	N/A	0.00	1.19	0.52	0.92
33	N/A	0.00	1.69	0.40	0.85
34	N/A	0.02	1.57	0.42	0.92

Syndromic / Influenza-like Illness Surveillance

Healthcare Practitioners Sentinel Surveillance

In week 45, 2.15% of visits to healthcare professionals were due to influenza-like illness (ILI). The sharp increase this week may be due to low number of sentinels reporting.

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.

FluWatchers

In week 45, 12,590 participants reported to FluWatchers, of which 0.6% reported symptoms of cough and fever (Figure 6). 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 COVID-19. 

The percentage of participants reporting cough and fever has been stable since week 37, and remains at lower than expected levels. This 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.

Among the 69 participants who reported cough and fever:

• 67% consulted a healthcare professional;
• 72% reported days missed from work or school, resulting in a combined total of 180 missed days of work or school (average of 2.5 days).

Nova Scotia had the highest participation rate this week (46 participants per 100,000 population) and the neighbourhood of K0A had the highest number of participants (140). 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.

Influenza Outbreak Surveillance

In week 45, no outbreaks were reported.

To date this season (August 28 to November 13, 2021), 11 ILI outbreaks and no laboratory-confirmed influenza outbreaks have been reported. The most recent laboratory-confirmed influenza outbreak occurred in week 24 (week ending June 13, 2020) of the 2019-2020 season.

All ILI outbreaks have been reported in schools and/or daycares. The number of ILI outbreaks reported to date this season is lower than the 2020-2021 season but higher than in pre-pandemic 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 respiratory syncytial virus, rhinovirus, and even COVID-19. Many respiratory viruses in addition to the flu commonly circulate during the fall, 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 45: 13 out of 13

Influenza Severe Outcomes Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 45, no influenza-associated hospitalizations were reported by participating provinces and territories^{Footnote 2}.

To date this season (August 28 to November 13, 2021), no influenza-associated hospitalizations were reported by participating provinces and territories.

The last influenza-associated hospitalization reported by participating provinces and territories was reported in week 25 (week ending June 20, 2020) of the 2019-2020 season.

Number of provinces and territories reporting in week 45: 9 out of 9

Pediatric Influenza Hospitalizations and Deaths

In week 45, no pediatric (≤16 years of age) influenza-associated hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network.

To date this season (August 28 to November 13, 2021), no pediatric influenza-associated hospitalizations were reported by the IMPACT network.

The last pediatric influenza-associated hospitalization was reported by the IMPACT network in week 29 (week ending July 18, 2020) of the 2019-2020 season.

Adult Influenza Hospitalizations and Deaths

In week 45, less than five influenza-associated adult (≥16 years of age) hospitalizations have been reported by the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) network. This is the first report of hospitalization(s) from the network since in week 19 (week ending May 9, 2020) of the 2019-2020 season.

To date this season (August 28 to November 13, 2021), less than five influenza-associated adult (≥16 years of age) hospitalizations have been reported by the CIRN SOS network.

Influenza Strain Characterization

The National Microbiology Laboratory has not yet reported influenza strain characterization results for influenza viruses collected during the 2021-2022 season.

Antiviral Resistance

The National Microbiology Laboratory has not yet reported antiviral resistance results for influenza viruses collected during the 2021-2022 season.

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 2021-2022 season are anticipated to be available in February or March 2022.

Vaccine Effectiveness

Influenza vaccine effectiveness estimates for the 2021-2022 season are anticipated to be available in February or March 2022, pending the resumption of community transmission of seasonal influenza.

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.