Overall Summary
- Overall in week 03, seasonal influenza activity increased from the previous week but remains below expected levels for this time of the year.
- Hospitalizations among the pediatric population increased in week 03.
- Influenza A(H1N1) is the most common influenza subtype circulating in Canada.
- Influenza strains characterized by the National Microbiology Laboratory this season appear to be a good match to the World Health Organization's recommended vaccine strains.
- For more information on the flu, see our Flu(influenza) web page.
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Organization: Public Health Agency of Canada
Date published: 2016-01-29
Related Topics
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On this page
- Influenza/ILI Activity (geographic spread)
- Laboratory Confirmed Influenza Detections
- Influenza-like Illness Consultation Rate
- Influenza Outbreak Surveillance
- Sentinel Pediatric Hospital Influenza Surveillance
- Provincial/Territorial Influenza Hospitalizations and Deaths
- Influenza Strain Characterizations
- Antiviral Resistance
- International Influenza Reports
- FluWatch definitions for the 2015-2016 season
In week 03, influenza/ILI activity increased in Canada. A total of 27 regions across Canada reported sporadic influenza/ILI activity. Localized activity was reported in six regions in Canada (one each in BC, AB and NS, and three in ON).
Figure 1. Map of overall influenza/ILI activity level by province and territory, Canada, Week 03
Note: Influenza/ILI activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates and reported outbreaks. Please refer to detailed definitions at the end of the report. Maps from previous weeks, including any retrospective updates, are available in the mapping feature found in the Weekly Influenza Reports.
Figure 1 - Text Description Laboratory Confirmed Influenza Detections
Laboratory confirmed influenza detections continue to increase steadily. The percent positive for influenza increased from 7.0% in week 02 to 12.4% in week 03 (Figure 2). Compared to the previous five seasons, the percent positive (12.4%) reported in week 03 was below the five year average for that week and below expected levels (range 13.2%-29.7%).
Figure 2. Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2015-16
Figure 2 - Text Description In week 03, there were 594 positive influenza tests reported. Influenza A(H1N1) was the most common subtype detected. The majority of influenza detections were reported from Western Canada, where BC and AB accounted for 69% of influenza detections in Canada in week 03. To date, 79% of influenza detections have been influenza A and among those subtyped, the majority have been influenza A(H1N1) [63% (744/1186)].Figure 3. Cumulative numbers of positive influenza specimens by type/subtype and province, Canada, 2015-16
Note: Specimens from NT, YT, and NU are sent to reference laboratories in other provinces. Cumulative data includes updates to previous weeks.Figure 3 - Text Description To date this season, detailed information on age and type/subtype has been received for 1,435 cases. Adults aged 65 years and older accounted for 27% of reported influenza cases (Table 1). Adults aged 65 years and older also represented 44% of reported A(H3N2) cases. Adults aged 20-44 years represented 26% of reported influenza A(H1N1) cases and 29% of reported influenza B cases.
| Table 1 - Footnote 1 Table 1 includes specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Return to Table 1 - Footnote1referrer Table 1 - Footnote 2 Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections. Return to Table 1 - Footnote2referrer Table 1 - Footnote UnS Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available. Return to Table 1 - FootnoteUnSreferrer |
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| 43 | 12 | 2 | 29 | 7 | 146 | 58 | 30 | 58 | 38 | 184 | 12.8% | |
| 21 | 5 | 1 | 15 | 44 | 107 | 30 | 45 | 32 | 115 | 222 | 15.5% | |
| 63 | 13 | 6 | 44 | 38 | 219 | 66 | 65 | 88 | 117 | 336 | 23.4% | |
| 33 | 5 | 2 | 26 | 13 | 230 | 61 | 89 | 80 | 68 | 298 | 20.8% | |
| 28 | 3 | 8 | 17 | 11 | 316 | 31 | 180 | 105 | 71 | 387 | 27.0% | |
| 1 | 1 | 0 | 0 | 0 | 7 | 5 | 2 | 0 | 1 | 8 | 0.6% | |
| 189 | 39 | 19 | 131 | 113 | 1025 | 251 | 411 | 363 | 410 | 1435 | 100.0% | |
| 62.6% | 20.6% | 10.1% | 69.3% | 37.4% | 71.4% | 24.5% | 40.1% | 35.4% | 28.6% | |||
Influenza-like Illness Consultation Rate
The national ILI consultation rate increased from the previous week from 12.5 per 1,000 patient visits in week 02, to 15.6 per 1,000 patient visits in week 03. In week 03, the highest ILI consultation rate was found in those 0-4 years of age (26.9 per 1,000) and the lowest was found in the ≥65 years age group (2.7 per 1,000) (Figure 4).
Figure 4. Influenza-like-illness (ILI) consultation rates by age group and week, Canada, 2015-16
Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.Figure 4 - Text Description Influenza Outbreak Surveillance
In week 03, six new laboratory confirmed influenza outbreaks: four in long-term care facilities (LTCF), one in a hospital and one in an institutional or community setting. Two outbreaks were due to influenza B, one outbreak was due to influenza A (UnS) and the remainder were unknown. To date this season, 46 outbreaks have been reported (23 of which occurred in LTCFs). In comparison, at week 03 in the 2014-15 season, 941 outbreaks were reported (741 of which occurred in LTCFs) and in the 2013-14 season, 60 outbreaks were reported (33 of which occurred in LTCFs).
Figure 5. Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote1 by report week, Canada, 2015-2016
Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of the report.Return to Figure 5 - Footnote1referrer
Figure 5 - Text Description Sentinel Pediatric Hospital Influenza Surveillance
Paediatric Influenza Hospitalizations and Deaths
In week 03, 24 hospitalizations were reported by the the Immunization Monitoring Program Active (IMPACT) network (Figure 6). Nine hospitalizations were due to influenza A(H1N1) (38%), five were due to influenza B (21%) and the remainder were influenza A (UnS).
To date this season, 94 laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations have been reported by the IMPACT network. Seventy-one hospitalized cases were due to influenza A and 23 cases were due to influenza B. The majority of hospitalized cases were among children aged 2-4 years (32%). To date, 13 intensive care unit (ICU) admissions have been reported. The majority of ICU admissions were reported in children 2-4 years (46%) and due to influenza A(H1N1) (38%). Less than five influenza-associated deaths have been reported.
| 11 | 2 | 2 | 7 | 5 | 16 (17%) |
| 17 | 9 | 3 | 5 | 4 | 21 (22%) |
| 24 | 10 | 2 | 12 | 6 | 30 (32%) |
| 10 | 4 | 0 | 6 | 6 | 16 (17%) |
| 10 | 4 | 0 | 6 | 6 | 11 (12%) |
| 71 | 28 | 8 | 35 | 23 | 94 (100%) |
Not included in Table 2 and Figure 6 are two IMPACT cases that were due to co-infections of influenza A and B.Figure 6 - Text Description Adult Influenza Hospitalizations and Deaths
In week 03, 15 hospitalizations were reported by the Canadian Immunization Research Network Serious Outcome Surveillance (CIRN-SOS). The majority of hospitalizations were in adults 45-64 years of age (47%) and due to influenza A (73%).
To date this season, 71 laboratory-confirmed influenza-associated adult (≥16 years of age) hospitalizations have been reported by CIRN-SOS (Table 3). The majority of hospitalized cases were due to influenza A (77%) and were among adults ≥65 years of age (49%). Five intensive care unit (ICU) admissions have been reported and among those, four (80%) were due to influenza A. No deaths have been reported.
| 1 | 1 | 0 | 0 | 0 | 1 (1%) |
| 4 | 1 | 0 | 3 | 7 | 11 (15%) |
| 17 | 3 | 2 | 12 | 5 | 22 (31%) |
| 32 | 2 | 12 | 18 | 3 | 35 (49%) |
| 1 | 0 | 0 | 1 | 1 | 2 (3%) |
| 55 | 7 | 14 | 34 | 16 | 71 |
| 77% | 13% | 25% | 62% | 23% | 100% |
Note: The number of hospitalizations reported through CIRN-SOS and IMPACT represents a subset of all influenza-associated adult and paediatric hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.Figure 7 - Text Description Provincial/Territorial Influenza Hospitalizations and Deaths
In week 03, 51 hospitalizations have been reported from participating provinces and territoriesFootnote*. The majority of hospitalizations were due to influenza A (86%) and reported in the 0-4 years age group (35%).
Since the start of the 2015-16 season, 343 laboratory-confirmed influenza-associated hospitalizations have been reported. Two hundred and ninety-nine hospitalizations (87%) were due to influenza A and 44 (13%) were due to influenza B. Among cases for which the subtype of influenza A was reported, 69% (129/187) were influenza A(H1N1). The majority (37%) of hospitalized cases were ≥65 years of age. Thirty-two ICU admissions have been reported of which 26 (82%) were due to influenza A and 12 (38%) were in the 45-64 age group. A total of 14 deaths have been reported, all due to influenza A.
Figure 8. Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada 2015-16
Figure 8 - Text Description Footnote * Note: Influenza-associated hospitalizations are not reported to PHAC by the following Provinces and Territory: BC, NU, and QC. Only hospitalizations that require intensive medical care are reported by SK. ICU admissions are not distinguished among hospital admissions reported from ON. Data may also include cases reported by the IMPACT networks. The number of new influenza-associated hospitalizations and deaths reported for the current week may include cases from ON that occurred in previous weeks, as a result of retrospective updates to the cumulative total. It is important to note that the hospitalization or death does not have to be attributable to influenza, a positive laboratory test is sufficient for reporting.Return to footnote*referrer
See additional data on Reported Influenza Hospitalizations and Deaths in Canada: 2011-12 to 2015-16 on the Public Health Agency of Canada website.
Influenza Strain Characterizations
During the 2015-16 influenza season, the National Microbiology Laboratory (NML) has characterized 234 influenza viruses [100 A(H3N2), 94 A(H1N1) and 40 influenza B].
Influenza A (H3N2): When tested by hemagglutination inhibition (HI) assays, twelve H3N2 virus were antigenically characterized as A/Switzerland/9715293/2013-like using antiserum raised against cell-propagated A/Switzerland/9715293/2013.
Sequence analysis was done on 88 H3N2 viruses. All viruses belonged to a genetic group for which most viruses were antigenically related to A/Switzerland/9715293/2013.
A/Switzerland/9715293/2013 is the A(H3N2) component of the 2015-16 Northern Hemisphere's vaccine.
Influenza A (H1N1): Ninety-four H1N1 viruses characterized were antigenically similar to A/California/7/2009, the A(H1N1) component of the 2015-16 influenza vaccine.
Influenza B: Twenty-five influenza B viruses characterized were antigenically similar to the vaccine strain B/Phuket/3073/2013. Fifteen influenza B viruses were characterized as B/Brisbane/60/2008-like, one of the influenza B components of the 2015-16 Northern Hemisphere quadrivalent influenza vaccine.
The recommended components for the 2015-2016 northern hemisphere trivalent influenza vaccine include: an A/California/7/2009(H1N1)pdm09-like virus, an /Switzerland/9715293/2013(H3N2)-like virus, and a B/Phuket/3073/2013 -like virus (Yamagata lineage). For quadrivalent vaccines, the addition of a B/Brisbane/60/2008-like virus (Victoria lineage) is recommended.
The NML receives a proportion of the number of influenza positive specimens from provincial laboratories for strain characterization and antiviral resistance testing. Characterization data reflect the results of haemagglutination inhibition testing compared to the reference influenza strains recommended by WHO.
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Figure 2 - Text Description In week 02, there were 355 positive influenza tests reported. Similar to previous weeks, influenza A was the most frequently detected influenza type nationally with influenza A(H1N1) the most common subtype detected.The majority of influenza detections were reported from Western Canada, where BC and AB accounted for 71% of influenza detections in Canada in week 02. To date, 82% of influenza detections have been influenza A and among those subtyped over half have been influenza A(H1N1) [55% (473/859)].
Note: Specimens from NT, YT, and NU are sent to reference laboratories in other provinces. Cumulative data includes updates to previous weeks.
Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.
Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of the report.
Figure 6 - Text Description Adult Influenza Hospitalizations and Deaths
Figure 7 - Text Description Provincial/Territorial Influenza Hospitalizations and Deaths
Figure 8 - Text Description Footnote * Note: Influenza-associated hospitalizations are not reported to PHAC by the following Provinces and Territory: BC, NU, and QC. Only hospitalizations that require intensive medical care are reported by Saskatchewan. ICU admissions are not distinguished among hospital admissions reported from Ontario. Data may also include cases reported by the IMPACT networks. The number of new influenza-associated hospitalizations and deaths reported for the current week may include cases from Ontario that occurred in previous weeks, as a result of retrospective updates to the cumulative total. It is important to note that the hospitalization or death does not have to be attributable to influenza, a positive laboratory test is sufficient for reporting.
Figure 2 - Text Description In week 01, there were 306 positive influenza tests reported. Similar to the previous two weeks, the majority of subtyped influenza A viruses detected in Canada were influenza A(H1N1). Influenza A(H1N1) was the most common influenza A subtype detected in AB, SK, ON, NB, and PE in week 01. To date, 83% of influenza detections have been influenza A and among those subtyped approximately half have been influenza A(H3N2) [52% (344/659)].
Note: Specimens from NT, YT, and NU are sent to reference laboratories in other provinces. Cumulative data includes updates to previous weeks.
Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.
Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of the report.
Figure 6 - Text Description Adult Influenza Hospitalizations and Deaths
Figure 7 - Text Description Provincial/Territorial Influenza Hospitalizations and Deaths
Figure 8 - Text Description Footnote * Note: Influenza-associated hospitalizations are not reported to PHAC by the following Provinces and Territory: BC, NU, and QC. Only hospitalizations that require intensive medical care are reported by Saskatchewan. ICU admissions are not distinguished among hospital admissions reported from Ontario. Data may also include cases reported by the IMPACT networks. The number of new influenza-associated hospitalizations and deaths reported for the current week may include cases from Ontario that occurred in previous weeks, as a result of retrospective updates to the cumulative total. It is important to note that the hospitalization or death does not have to be attributable to influenza, a positive laboratory test is sufficient for reporting.
Figure 2 - Text Description In week 44, there were 40 laboratory detections of influenza reported (up from 28 detections reported in week 43). BC accounted for 53% (n=21) of the influenza detections in Canada in week 44. To date, 91% of influenza detections have been influenza A and the majority of those subtyped have been A(H3) (87%).
Note: Specimens from NT, YT, and NU are sent to reference laboratories in other provinces. Cumulative data includes updates to previous weeks.
Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.
Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of the report.
Figure 6 - Text Description Figure 7. Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2015-16 paediatric hospitalizations (≤16 years of age, IMPACT)
Note: The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated paediatric hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 8 - Text Description See additional data on 
Figure 2 - Text Description There were 28 laboratory cases of influenza reported in week 43. The majority of influenza detections have been reported from BC and ON, accounting for 79% of the influenza detections in Canada. To date, 90% of influenza detections have been influenza A and the majority of those subtyped have been A(H3) (88%).
Note: Specimens from NT, YT, and NU are sent to reference laboratories in other provinces. Cumulative data includes updates to previous weeks.
Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data is compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.
Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of the report.
Figure 6 - Text Description Figure 7. Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2015-16 Paediatric hospitalizations (≤16 years of age, IMPACT)
Note: The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated paediatric hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 8 - Text Description See additional data on 
Figure 2 - Text Description In week 42, the majority of detections in Canada have been reported from BC and ON, accounting for 75% of the influenza detections in Canada. A total of six jurisdictions have not reported any influenza cases. To date, 92% of influenza detections have been influenza A and the majority of those subtyped have been A(H3).
Note: Specimens from NT, YT, and NU are sent to reference laboratories in other provinces. Cumulative data includes updates to previous weeks.
Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data is compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.
Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of the report.
Figure 6 - Text Description Figure 7. Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2015-16 Paediatric hospitalizations (≤16 years of age, IMPACT)
Note: The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated paediatric hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 8 - Text Description See additional data on 
Figure 2 - Text Description In week 41, the majority of detections in Canada have been reported from BC, AB, and ON, accounting for 86% of the influenza detections in Canada. A total of six jurisdictions have yet to report any influenza cases. To date, 92% of influenza detections have been influenza A and the majority of those subtyped have been A(H3).
Note: Specimens from NT, YT, and NU are sent to reference laboratories in other provinces. Cumulative data includes updates to previous weeks.
Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data is compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.
Figure 5 - Footnote 1 All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of the report.
Figure 6 - Text Description Figure 7. Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2015-16 Paediatric hospitalizations (≤16 years of age, IMPACT)
Note: The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated paediatric hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
Figure 8 - Text Description See additional data on
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