FluWatch report: August 29 to September 25, 2021 (weeks 35-38)
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Organization: Public Health Agency of Canada
Date published: 2021-10-01
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Weekly Highlights
- In week 38, influenza activity across Canada was exceptionally low, with all regions reporting no influenza activity. For the past four weeks, all influenza indicators were at exceptionally low interseasonal levels.
Virologic
- In the past four weeks, a total of eight influenza detections have been reported; all were influenza A.
- Among the six detections with detailed age information, all were reported in individuals under the age of 65 years.
Syndromic
- The percentage visits for influenza-like illness (ILI) was 0.8% in week 38 and is within expected levels.
- The percentage of FluWatchers reporting fever and cough was 0.6% in week 38; it remains below expected levels but is trending up.
Outbreaks
- In the past four weeks, 11 ILI outbreaks in schools and/or daycares were reported.
- From August 29 to September 25, 2021 (weeks 35 to 38), no laboratory-confirmed influenza outbreaks have been reported.
Severe Outcomes
- From August 29 to September 25, 2021 (weeks 35 to 38), no influenza-associated hospitalizations have been reported.
Other Notes
- This is the first FluWatch report of the 2021-2022 surveillance season. The next report will be published on October 15, 2021.
- Weekly reporting of laboratory detections of respiratory viruses will continue via our Respiratory Virus Detections Surveillance System.
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
During week 38, all regions reported no influenza/ILI activity (Figure 1).
Figure 1 – Map of influenza/ILI activity by province and territory, Canada, week 2021-38
Number of Regions Reporting in Week 38: 47 out of 53
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 Data |
| 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 Data |
| N.W.T. | South | No Data |
| Nvt. | Qikiqtaaluk | No Data |
| Nvt. | Kivalliq | No Data |
| Nvt. | Kitimeot | No Data |
Laboratory-Confirmed Influenza Detections
In weeks 35 to 38, eight laboratory detections of influenza were reported and all were influenza A.
Overall, the percentage of laboratory tests positive for influenza remains at exceptionally low levels, despite the elevated levels of testing seen this month. In weeks 35 to 38, 32,190 tests for influenza were performed at reporting laboratories and the average percentage of tests positive for influenza was 0.1%. Compared to the past six pre-pandemic seasons (2014-2015 to 2019-2020), an average of 8,049 tests were performed for this time period, with an average of 1.1% of tests positive for influenza (Figure 3).
To date this season (August 28 to September 25, 2021), eight influenza detections have been reported, which is lower than what we have seen historically in the past six pre-pandemic seasons, where an average of 87 influenza detections were reported at this point in the season.
Detailed information on age and type/subtype has been received for six laboratory-confirmed influenza detections. Among the six detections, all were in individuals under the age of 65.
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.
Figure 2 – Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, weeks 2021-35 to 2021-38
Number of Laboratories Reporting in Week 38: 32 out of 34
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 | 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 |
Figure 3 – Number of influenza tests and percentage of tests positive in Canada compared to previous seasons, weeks 2021-35 to 2021-38
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 equivalent
| Surveillance Week | Number of Tests, 2021-2022 | Number of Tests, 2020-21 | 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 | 8899 | 5335 | 2631 | 1778 | 2135 |
| 38 | 8709 | 6024 | 3039 | 1987 | 2502 |
| Surveillance Week | Percentage of tests positive, 2021-2022 | Percentage of tests positive, 2020-21 | 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 |
Syndromic / Influenza-like Illness Surveillance
Healthcare Practitioners Sentinel Surveillance
In week 38, 0.8% of visits to healthcare professionals were due to influenza-like illness (ILI). Since the beginning of the season, the percentage of visits for ILI has been within expected pre-pandemic levels (Figure 4).
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.
Figure 4 – Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2021-35 to 2021-38
Number of Sentinels Reporting in Week 38: 53
The shaded area represents the maximum and minimum percentage of visits for ILI 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 4 - Text equivalent
| Surveillance Week | 2021-2022 | 2020-2021 | Average | Min | Max |
|---|---|---|---|---|---|
| 35 | 0.5% | 0.1% | 0.6% | 0.4% | 0.9% |
| 36 | 1.1% | 0.2% | 0.6% | 0.4% | 0.9% |
| 37 | 0.5% | 0.4% | 0.7% | 0.5% | 1.0% |
| 38 | 0.8% | 0.3% | 0.7% | 0.6% | 1.0% |
FluWatchers
In week 38, 11,300 participants reported to FluWatchers, of which 0.6% reported symptoms of cough and fever (Figure 5). The reports of cough and fever 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.
The percentage of participants reporting cough and fever has been on an upward trend; however, it 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 62 participants who reported cough and fever:
- 73% consulted a healthcare professional;
- 87% reported days missed from work or school, resulting in a combined total of 171 missed days of work or school (average of 3.2 days per symptomatic participant).
Nova Scotia had the highest participation rate this week (42 participants per 100,000 population) and the neighbourhood of K0A had the highest number of participants (126). 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.
Figure 5 – Percentage of FluWatchers reporting cough and fever, Canada, weeks 2021-35 to 2021-38
Number of Participants Reporting in Week 38: 11,300
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 equivalent
| 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 | 0.55% | 0.29% | N/A | N/A | N/A |
Influenza Outbreak Surveillance
In weeks 35 to 38, 11 influenza-like illness (ILI) outbreaks were reported in schools and/or daycares from participating provincesFootnote 1.
To date this season (August 28 to September 25, 2021), eight 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 comparable to 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 reporting in week 37: 13 out of 13
Influenza Severe Outcomes Surveillance
Provincial/Territorial Influenza Hospitalizations and Deaths
In weeks 35 to 38, no influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote 2.
To date this season (August 28 to September 25, 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 of the 2019-2020 season.
Number of provinces and territories reporting in week 37: 4 out of 9
Pediatric Influenza Hospitalizations and Deaths
In weeks 35 to 38, 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 September 25, 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
Surveillance of influenza-associated adult (≥16 years of age) hospitalizations by the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) network for the 2021-2022 season begins in week 45 (November).
The last influenza-associated adult hospitalization was reported by the CIRN SOS network in week 19 (week ending May 9, 2020) of the 2019-2020 season.
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.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.
- 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 and other facilities.
- 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.
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