FluWatch report: October 25 to October 31, 2015 (week 43)
- Overall, Canada continues to experience low influenza activity, which is normally seen at this time of year
- One new laboratory confirmed outbreak was reported in week 43.
- So far this season, influenza A(H3N2) has been the most common subtype affecting Canadians – it is too early in the season to know if this is likely to continue.
- To date, the majority of influenza laboratory detections and hospitalizations have been in seniors greater than 65 years of age.
- For more information on the flu, see our Flu (influenza) web page.
Are you a primary health care practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel for the 2015-16 influenza season? Contact us at FluWatch@phac-aspc.gc.ca
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
Influenza/Influenza-like Illness Activity (geographic spread)
In week 43, sporadic influenza activity was reported in a few regions across Canada (NS, QC, ON, AB and BC). One region in Ontario and two regions in BC reported localized activity. Overall, the majority of regions in Canada reported no influenza activity.
Figure 1 - Text Description
Laboratory Confirmed Influenza Detections
The percent positive for influenza detections increased from 0.88% in week 42 to 1.0% in week 43 (Figure 2).
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%).
Among influenza cases with reported age, the largest proportion was in those ≥65 years of age (50%) (Table 1).
|Age groups (years)||Weekly (October 25 to October 31, 2015)||Cumulative (August 30, 2015 to October 31, 2015)|
|Influenza A||B||Influenza A||B||Influenza A and B|
|A Total||A(H1) pdm09||A(H3)||A Table 1 - Footnote UnS||Total||A Total||A(H1) pdm09||A(H3)||A Table 1 - Footnote UnS||Total||#||%|
|PercentageTable 1 - Footnote 2||82.4%||0.0%||7.1%||92.9%||17.6%||90.9%||8.0%||64.5%||27.5%||9.1%|
For additional data on other respiratory virus detections see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada website.
Influenza-like Illness Consultation Rate
The national influenza-like-illness (ILI) consultation rate decreased from 31.4 consultations per 1,000 patient visits in week 42 to 17.5 per 1,000 visits in week 43. In week 43, the highest ILI consultation rate was found in the 20-64 age group and the lowest was found in the ≥65 years of age group (Figure 4).
Influenza Outbreak Surveillance
In week 43, one new laboratory-confirmed outbreak of influenza was reported in a long-term care facility (LTCF) (Figure 5). An additional two outbreaks of ILI were reported in schools. To date this season, eight outbreaks have been reported (6 of which occurred in LTCFs). Last year at this time, 14 outbreaks were reported (13 of which occurred in LTCFs).
Figure 5. Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote 1 by report week, Canada, 2015-2016
Sentinel Pediatric Hospital Influenza Surveillance
Paediatric Influenza Hospitalizations and Deaths (IMPACT)
To date this season, six laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations have been reported by the Immunization Monitoring Program Active (IMPACT) network. Four hospitalized cases were due to influenza A and 2 cases were due to influenza B. To date, less than five ICU admissions have been reported.
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 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.
Provincial/Territorial Influenza Hospitalizations and Deaths
Since the start of the 2015-16 season, 39 laboratory-confirmed influenza-associated hospitalizations were reported from participating provinces and territoriesFootnote *. All but four hospitlaizations were due to influenza A. The majority (56%) of patients were ≥65 years of age. Four ICU admissions have been reported.
Figure 8. Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada 2015-16
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 22 influenza viruses [15 A(H3N2), 1 A(H1N1) and 6 influenza B].
Influenza A (H3N2):When tested by hemagglutination inhibition (HI), one H3N2 virus was antigenically characterized as A/Switzerland/9715293/2013-like using antiserum raised against cell-propagated A/Switzerland/9715293/2013.
Sequence analysis was done on 14 H3N2 viruses. All 14 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 Northern Hemisphere's vaccine.
Influenza A (H1N1): One H1N1 virus characterized was antigenically similar to A/California/7/2009, the A(H1N1) component of the 2015-16 influenza vaccine.
Influenza B: The six 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.
During the 2015-16 season, the National Microbiology Laboratory (NML) has tested 24 influenza viruses for resistance to oseltamivir and zanamivir. All viruses were sensitive to zanamivir and oseltamivir. All influenza A viruses tested (n=22) were resistant to amantadine (Table 2).
|Virus type and subtype||Oseltamivir||Zanamivir||Amantadine|
|# tested||# resistant (%)||# tested||# resistant (%)||# tested||# resistant (%)|
|A (H3N2)||18||0||18||0||21||21 (100%)|
|A (H1N1)||1||0||1||0||1||1 (100%)|
|B||5||0||5||0||NA Table 2 - Footnote *||NA Table 2 - Footnote *|
International Influenza Reports
- World Health Organization influenza update
- World Health Organization FluNet
- WHO Influenza at the human-animal interface
- Centers for Disease Control and Prevention seasonal influenza report
- European Centre for Disease Prevention and Control - epidemiological data
- South Africa Influenza surveillance report
- New Zealand Public Health Surveillance
- Australia Influenza Report
- Pan-American Health Organization Influenza Situation Report
FluWatch definitions for the 2015-2016 season
Abbreviations: Newfoundland/Labrador (NL), Prince Edward Island (PE), New Brunswick (NB), Nova Scotia (NS), Quebec (QC), Ontario (ON), Manitoba (MB), Saskatchewan (SK), Alberta (AB), British Columbia (BC), Yukon (YT), Northwest Territories (NT), Nunavut (NU).
Influenza-like-illness (ILI): Acute onset of respiratory illness with fever and cough and with one or more of the following - sore throat, arthralgia, myalgia, or prostration which is likely due to influenza. In children under 5, gastrointestinal symptoms may also be present. In patients under 5 or 65 and older, fever may not be prominent.
Greater than 10% absenteeism (or absenteeism that is higher (e.g. >5-10%) than expected level as determined by school or public health authority) which is likely due to ILI.
Note: it is recommended that ILI school outbreaks be laboratory confirmed at the beginning of influenza season as it may be the first indication of community transmission in an area.
- Hospitals and residential institutions:
- two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case. Institutional outbreaks should be reported within 24 hours of identification. Residential institutions include but not limited to long-term care facilities ( LTCF) and prisons.
- Greater than 10% absenteeism on any day which is most likely due to ILI.
- Other settings:
- two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case; i.e. closed communities.
Note that reporting of outbreaks of influenza/ILI from different types of facilities differs between jurisdictions.
Influenza/ILI activity level
1 = No activity: no laboratory-confirmed influenza detections in the reporting week, however, sporadically occurring ILI may be reported
2 = Sporadic: sporadically occurring ILI and lab confirmed influenza detection(s) with no outbreaks detected within the influenza surveillance region Footnote †
3 = Localized:
4 = Widespread:
Note: ILI data may be reported through sentinel physicians, emergency room visits or health line telephone calls.
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