FluWatch report: October 11 to October 17, 2015 (week 41)
Overall Summary
- Overall, there is low influenza activity in Canada.
- Influenza activity and detections decreased from the previous week.
- In week 41, no new influenza outbreaks were reported.
- So far this season, influenza A(H3N2) has been the most common subtype affecting Canadians.
- For more information on the flu, see our Flu (influenza) web page.
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Organization: Public Health Agency of Canada
Date published: 2015-10-23
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 41, sporadic influenza activity were reported in a few regions across Canada. One region in Ontario reported localized activity. Overall, the majority of regions in Canada have reported no influenza activity.
Figure 1. Map of overall influenza/ILI activity level by province and territory, Canada, Week 41
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 on the Flu Activity website.
Figure 1 - Text Description Laboratory Confirmed Influenza Detections
The number of positive influenza tests decreased from the previous week. In week 41, the percent positive for influenza detections remained low at 1.4%; however, this is the highest recorded value compared the previous five seasons during the same period (Figure 2).
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 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).
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 Among cases with reported age, the largest proportion was in those ≥65 years of age (48%) (Table 1). Compared to the previous year during the same period, a greater proportion of cases in the 20-44 and 45-64 age groups have been reported to date (39% this year vs 22% last year).
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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1 | 0 | 1 | 0 | 0 | 7 | 1 | 6 | 0 | 1 | 8 | 4.4% | |
0 | 0 | 0 | 0 | 0 | 9 | 1 | 5 | 3 | 4 | 13 | 7.1% | |
3 | 1 | 0 | 2 | 0 | 22 | 5 | 9 | 8 | 3 | 25 | 13.7% | |
1 | 0 | 0 | 1 | 0 | 44 | 7 | 27 | 10 | 3 | 47 | 25.8% | |
11 | 0 | 6 | 5 | 2 | 84 | 2 | 59 | 23 | 4 | 88 | 48.4% | |
0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 1 | 0.5% | |
16 | 1 | 7 | 8 | 2 | 167 | 16 | 107 | 44 | 15 | 182 | 100.0% | |
88.9% | 6.3% | 43.8% | 50.0% | 11.1% | 91.8% | 9.6% | 64.1% | 26.3% | 8.2% |
Influenza-like Illness Consultation Rate
The national influenza-like-illness (ILI) consultation rate increased from 17.1 consultations per 1,000 patient visits in week 40 to 22.3 per 1,000 visits in week 41. In week 41, the highest ILI consultation rate was found in the 0-4 age group and the lowest was found in the 5-19 age group (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 is 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 41, no new outbreaks of influenza were reported (Figure 5).
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 (IMPACT)
To date, less than five laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations have been reported by the Immunization Monitoring Program Active (IMPACT) network. All hospitalized cases were due to influenza A.
Figure 6. Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada, 2015-16, Paediatric hospitalizations (≤16 years of age, IMPACT)
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 7 - Text Description Provincial/Territorial Influenza Hospitalizations and Deaths
Since the start of the 2015-16 season, 30 laboratory-confirmed influenza-associated hospitalizations were reported from participating provinces and territoriesFootnote*. All but one hospitlaization was due to influenza A. The majority of were patients ≥65 years of age. Three ICU admissions have been reported.
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.
Return to footnote*referrer
Figure 8. Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada 2015-16
Figure 8 - Text Description 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 eight influenza viruses [5 A(H3N2) and 3 influenza B].
Influenza A (H3N2): Sequence analysis of the H3N2 viruses showed that all five viruses belonged to a genetic group for which most viruses were antigenically related to A/Switzerland/9715293/2013, the A(H3N2) component of the Northern Hemisphere's vaccine.
Influenza B: The three influenza B viruses characterized were antigenically similar to the vaccine strain B/Phuket/3073/2013.
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 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 (HAI) testing compared to the reference influenza strains recommended by WHO.
Antiviral Resistance
During the 2015-16 season, the National Microbiology Laboratory (NML) as tested nine influenza viruses for resistance to oseltamivir and zanamivir. All viruses were sensitive to zanamivir and oseltamivir. All influenza A viruses tested were resistant to amantadine (Table 2).
Table 2 - Footnote * NA - not applicable Return to Table 2 - Footnote*referrer |
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6 | 0 | 6 | 0 | 7 | 7 (100%) | |
0 | 0 | 0 | 0 | 0 | 0 | |
3 | 0 | 3 | 0 | NA Table 2 - Footnote* | NA Table 2 - Footnote* | |
9 | 0 | 9 | 0 | 7 | 7 |
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