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

thumbnail

Download the alternative format
(PDF format, 772 kb, 7 pages)

Organization: Public Health Agency of Canada

Date published: 2021-05-28

Related Topics

Overall Summary

  • Despite continued monitoring for influenza across Canada, there continues to be no evidence of community circulation of influenza. Given the time of year, influenza should remain at interseasonal levels.
  • Sign up to become a FluWatcher! FluWatchers provide valuable information on influenza and COVID-19 activity across Canada.
  • The next FluWatch report will be published on June 25, 2021. Weekly reporting of laboratory detections of respiratory viruses will continue via our Respiratory Virus Detections Surveillance System.

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 - Map of influenza/ILI activity by province and territory, Canada, week 2021-20

Number of Regions Reporting in Week 20: 45 out of 53

Figure 1. Text equivalent follows.

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.

Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2020-35 to 2021-20

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

Figure 2

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

Figure 3: Number of influenza tests (a) and percentage of tests positive (b) in Canada by week, weeks 2020-35 to 2021-20 as compared to previous seasons

figure 3

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.

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2020-35 to 2021-20

Number of Sentinels Reporting in Week 20: 54

Figure 4

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.

Figure 5 - Percentage of participants reporting fever and cough, Canada, weeks 2020-35 to 2021-20

Number of Participants Reporting in Week 20: 12,343

Figure 5. Text equivalent follows.

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
Online Figure - Geographic distribution of FluWatchers participants reporting cough and fever, Canada, week 2021-20

Click on the map to access the link

map

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 20Footnote 1: 11 out of 13

Footnote 1

All Provinces and Territories (PTs) participate in FluWatch's outbreak surveillance system. This outbreak system monitors influenza and ILI outbreaks in long-term care facilities, acute care facilities, schools and daycares, remote and/or isolated communities, and facilities categorized as 'other'. Not all reporting PTs report outbreaks in all these settings. All PTs report laboratory confirmed outbreaks in LTCF. Four PTs (NB, NL, NS and YK) report ILI outbreaks in schools and/or daycares.

Return to footnote 1 referrer

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 territoriesFootnote 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

Footnote 2

Influenza-associated hospitalizations are reported by Alberta, Manitoba, New Brunswick, Newfoundland and Labrador, Northwest Territories, Nova Scotia, Prince Edward Island and Yukon. Only hospitalizations that require intensive medical care are reported by Saskatchewan.

Return to footnote 2 referrer

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:

Table 1 – Influenza vaccine coverage among adults (n=3,032)Footnote * by risk groupFootnote and genderFootnote ,
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.

Report a problem or mistake on this page
Please select all that apply:

Thank you for your help!

You will not receive a reply. For enquiries, contact us.

Date modified: