FluWatch report: November 1, 2020 to November 7, 2020 (week 45)

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Organization: Public Health Agency of Canada

Date published: 2020-11-13

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Overall Summary

  • Influenza testing continues at elevated levels; however, influenza activity remains below average for this time of year.
  • Four laboratory detections of influenza were reported in week 45; two of these detections were associated with recent live attenuated influenza vaccine (LAIV) receipt and likely represent vaccine-type virus rather than community circulation of seasonal influenza viruses.
  • Four influenza-like-illness (ILI) outbreaks were reported in schools and daycares.
  • 12,258 participants reported to FluWatchers and 35 (0.29%) participants reported cough and fever. Provide valuable information to track the flu and COVID-19 across Canada: Sign up to become a FluWatcher!
  • Influenza surveillance indicators may be influenced by the COVID-19 pandemic, including changes in healthcare-seeking behaviour, impacts of public health measures and influenza testing capacity. Current data should be interpreted with consideration to this context. See the COVID-19 Epidemiology update for information on COVID-19 cases in Canada.

Influenza/Influenza-like Illness (ILI) Activity (geographic spread)

During week 45, no influenza/ILI activity was reported in Canda (Figure 1).

Influenza/ILI activity is lower at this point in the season compared to the previous four seasons; historically, between 22- 30 regions reported activity in week 45.

Figure 1 - Map of influenza/ILI activity by province and territory, Canada, week 2020-45

Number of Regions Reporting in Week 45: 53 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 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 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 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 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 week 45, four laboratory detections of influenza were reported (Figure 2). Two of these influenza detections were known to be associated with recent live attenuated influenza vaccine (LAIV) receipt in two individuals and likely represent vaccine-type virus rather than 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).

The percentage of laboratory tests positive for influenza has remained at exceptionally low levels throughout the period of March to October, despite elevated levels of testing. In week 45, 9,985 tests for influenza were performed at reporting laboratories, which is 2.2 times the average for this week over the past six seasons. The percentage of tests positive for influenza in week 45 was 0.04%, compared to 4.6% during the past six seasons.

To date this season, 17 influenza detections have been reported, which is significantly lower than the past six seasons where an average of 818 influenza detections were reported between weeks 35-45.

The 2019-20 influenza season in Canada ended abruptly in mid-March, concurrent with the implementation of public health measures to reduce the spread of COVID-19. 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 2020-45

Number of laboratories reporting in week 45: 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. Note some of the laboratory detections reported in weeks 44 and 45 were associated with recent live attenuated influenza vaccine receipt and likely represent vaccine-type virus rather than community circulation of seasonal influenza.

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 1 0.0 0.0
44 3 0 0 3 0.0 0.0
45 1 0 0 2 0.0 0.0

Figure 3 - Distribution of positive influenza specimens by type/subtype and province/territoryFootnote *, Canada, weeks 2020-35 to 2020-45

There is insufficient data for weeks 35-45 to present influenza detections by type/subtype and province/territory.

Footnote *

Specimens from NWT, YT, and Nvt are sent to reference laboratories in other provinces.

Return to footnote * referrer

Syndromic / Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 45, 0.6% of visits to healthcare professionals were due to influenza-like illness (ILI) which is similar to previous weeks, and 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 2020-45

Number of participants reporting in week 45: 63

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 2019-2020 Average Min Max
35 0.1% 0.6% 0.4% 0.9%
36 0.2% 0.6% 0.4% 0.9%
37 0.4% 0.7% 0.5% 1.0%
38 0.3% 0.7% 0.6% 1.0%
39 0.4% 0.9% 0.5% 1.2%
40 0.2% 1.2% 0.8% 1.7%
41 0.4% 1.7% 0.8% 2.8%
42 0.6% 1.6% 1.2% 2.1%
43 0.4% 1.2% 0.8% 1.7%
44 0.5% 1.2% 0.7% 1.7%
45 0.6% 1.2% 0.9% 1.5%
46 #N/A 1.4% 1.2% 1.8%
47 #N/A 1.6% 1.1% 2.2%
48 #N/A 1.5% 1.1% 2.2%
49 #N/A 1.7% 1.0% 2.8%
50 #N/A 1.5% 1.1% 1.7%
51 #N/A 1.9% 1.4% 2.7%
52 #N/A 2.0% 1.0% 3.1%
1 #N/A 3.4% 1.9% 5.4%
2 #N/A 3.4% 1.8% 5.7%
3 #N/A 2.3% 1.3% 3.7%
4 #N/A 2.0% 1.1% 2.9%
5 #N/A 2.1% 1.4% 3.1%
6 #N/A 2.4% 1.4% 4.0%
7 #N/A 2.4% 0.9% 3.5%
8 #N/A 2.3% 0.8% 3.4%
9 #N/A 2.3% 0.9% 3.1%
10 #N/A 2.0% 1.0% 2.8%
11 #N/A 1.9% 1.1% 2.8%
12 #N/A 1.6% 0.6% 2.6%
13 #N/A 1.6% 1.1% 2.6%
14 #N/A 1.7% 1.1% 3.0%
15 #N/A 1.3% 0.9% 1.9%
16 #N/A 1.2% 0.8% 1.7%
17 #N/A 1.2% 0.7% 1.7%
18 #N/A 1.3% 0.5% 2.0%
19 #N/A 0.9% 0.6% 1.3%
20 #N/A 1.1% 0.6% 1.5%
21 #N/A 0.9% 0.5% 1.3%
22 #N/A 0.7% 0.3% 1.0%
23 #N/A 0.8% 0.6% 1.0%
24 #N/A 0.7% 0.6% 1.0%
25 #N/A 0.6% 0.4% 0.8%
26 #N/A 0.8% 0.5% 1.4%
27 #N/A 0.6% 0.5% 0.7%
28 #N/A 0.7% 0.5% 1.3%
29 #N/A 0.9% 0.6% 1.7%
30 #N/A 0.6% 0.2% 0.9%
31 #N/A 0.4% 0.2% 0.6%
32 #N/A 0.8% 0.3% 1.2%
33 #N/A 0.7% 0.4% 1.3%
34 #N/A 0.7% 0.4% 1.5%

FluWatchers

In week 45, 12,258 participants reported to FluWatchers. A total of 35 participants (0.29%) reported symptoms of cough and fever (Figure 5). The percentage of participants reporting cough and fever is 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 2020-45

Number of participants reporting in week 45: 12,258

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 0.24% 1.57% 1.39% 1.78%
45 0.29% 1.83% 1.42% 2.32%
46 0.00% 1.83% 1.22% 2.15%
47 0.00% 1.93% 1.44% 2.39%
48 0.00% 2.43% 1.67% 3.35%
49 0.00% 2.56% 1.97% 3.16%
50 0.00% 2.91% 2.12% 3.79%
51 0.00% 3.18% 2.53% 3.95%
52 0.00% 3.98% 2.81% 5.38%
1 0.00% 3.84% 2.85% 4.76%
2 0.00% 2.94% 1.90% 3.93%
3 0.00% 3.25% 2.35% 4.84%
4 0.00% 3.12% 2.13% 4.23%
5 0.00% 3.19% 2.62% 3.59%
6 0.00% 3.47% 2.76% 4.28%
7 0.00% 3.18% 2.58% 3.79%
8 0.00% 3.09% 2.54% 3.65%
9 0.00% 2.81% 2.38% 3.53%
10 0.00% 2.58% 2.12% 3.11%
11 0.00% 2.33% 1.89% 2.63%
12 0.00% 2.60% 2.46% 2.82%
13 0.00% 2.48% 1.99% 3.06%
14 0.00% 2.13% 1.35% 2.58%
15 0.00% 1.78% 1.60% 1.93%
16 0.00% 2.00% 1.47% 2.44%
17 0.00% 1.73% 1.40% 2.31%
18 0.00% 1.50% 1.19% 2.09%
19 0.00% N/A N/A N/A
20 0.00% N/A N/A N/A
21 0.00% N/A N/A N/A
22 0.00% N/A N/A N/A
23 0.00% N/A N/A N/A
24 0.00% N/A N/A N/A
25 0.00% N/A N/A N/A
26 0.00% N/A N/A N/A
27 0.00% N/A N/A N/A
28 0.00% N/A N/A N/A
29 0.00% N/A N/A N/A
30 0.00% N/A N/A N/A
31 0.00% N/A N/A N/A
32 0.00% N/A N/A N/A
33 0.00% N/A N/A N/A
34 0.00% N/A N/A N/A
Online Figure - Geographic distribution of FluWatchers participants reporting cough and fever, Canada, week 2020-45

Click on the map to access the link

map

Influenza Outbreak Surveillance

In week 45, four influenza-like-illness (ILI) outbreaks were reported in schools and/or daycares. No other influenza or ILI outbreaks were reported in any other settings.

To date this season, 77 influenza-like-illness (ILI) outbreaks in schools and/or daycares, and one laboratory-confirmed influenza outbreak in a LTCF, have been reported.

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 even COVID-19. Rhinovirus commonly circulates during the fall, and can cause clusters of cases with respiratory illness that 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 Report.

Number of provinces and territories reporting in week 45Footnote 1: 13 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 week 45, no influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote 1. To date no influenza-associated hospitalizations were reported by participating provinces and territories.

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

Footnote 1

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 1 referrer

Pediatric Influenza Hospitalizations and Deaths

In week 45, 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 Hospitalizations 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 2020-21 season.

Influenza Strain Characterizations

Due to the very low influenza circulation to date this season, the National Microbiology Laboratory has not yet received influenza viruses collected during the 2020-21 season for strain characterization.

Antiviral Resistance

Due to the very low influenza circulation to date this season, the National Microbiology Laboratory has not yet received influenza viruses collected during the 2020-21 season for antiviral resistance testing.

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 2020-21 season are anticipated to be available in February or March 2021.

Vaccine Effectiveness

Influenza vaccine effectiveness estimates are typically available in February or March of each year; this may be delayed for the 2020-21 season if low influenza circulation continues.

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.

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