FluWatch report: November 15 to November 21, 2015 (week 46)
- Based on several indicators, influenza activity in Canada was low in week 46.
- Laboratory detections of influenza remain low and are below the five year average for week 46.
- There was a decrease in the number of regions reporting influenza activity.
- No new laboratory confirmed outbreaks were reported in week 46.
- So far this season, influenza A(H3N2) has been the most common subtype affecting Canadians.
- 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 46, 12 regions across Canada reported influenza/ILI (down from 19 regions in week 45). The majority of regions across Canada (41) reported no activity in week 46. Overall, very low flu activity was reported across the country.
Laboratory Confirmed Influenza Detections
The percent positive for influenza detections increased from 1.40% in week 45 to 1.52% in week 46. Compared to the previous five seasons, the percent positive (1.52%) reported in week 46 was below the five year average for that week but within expected levels (range 1.48% - 4.74%).
In week 46, there were 49 laboratory detections of influenza reported (up from 45 detections reported in week 45). BC and ON accounted for 71% of influenza detections in week 46. To date, 91% of influenza detections have been influenza A and the majority of those subtyped have been A(H3) (86%).
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.
Among influenza cases with reported age, the largest proportion was in those ≥65 years of age (50%) (Table 1).
|Age groups (years)||Weekly (November 15 to November 21, 2015)||Cumulative (August 30, 2015 to November 21, 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||100.0%||3.7%||51.9%||44.4%||0.0%||89.6%||7.4%||65.6%||27.0%||10.4%|
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 ILI consultation rate remained constant from the previous week. In week 46, the the ILI consultation rate was 21.1 per 1,000 patient visits. In week 46, the highest ILI consultation rate was found in the 20-64 age group and the lowest was found in the 4-19 years of age group (Figure 4).
Influenza Outbreak Surveillance
In week 46, two outbreaks of ILI were reported in schools To date this season, 15 outbreaks have been reported (ten of which occurred in LTCFs). Last year at this time, 19 outbreaks were reported (18 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
To date this season, ten laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations have been reported by the Immunization Monitoring Program Active (IMPACT) network. Six hospitalized cases were due to influenza A, two cases was due to influenza B. Two cases were due to co-infections of influenza A and B. To date, less than five intensive care unit (ICU) admissions have been reported.
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, 66 laboratory-confirmed influenza-associated hospitalizations were reported from participating provinces and territoriesFootnote *; all but eight with influenza A. Among cases for which the subtype of influenza A was reported, 76% (25/33) were A(H3). The majority (56%) of patients were ≥65 years of age. Five ICU admissions and two deaths have been reported. Both deaths reported were in adults. Last year, in week 46, a total of 110 hospitalizations were reported by participating provinces and territories.
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 36 influenza viruses [27 A(H3N2), 1 A(H1N1) and 8 influenza B].
Influenza A (H3N2): When tested by hemagglutination inhibition (HI) assays, 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 26 H3N2 viruses. All 26 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): One H1N1 virus characterized was antigenically similar to A/California/7/2009, the A(H1N1) component of the 2015-16 influenza vaccine.
Influenza B: Six influenza B viruses characterized were antigenically similar to the vaccine strain B/Phuket/3073/2013. Two influenza B virus was 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.
During the 2015-16 season, the National Microbiology Laboratory (NML) has tested 43 influenza viruses for resistance to oseltamivir and zanamivir. All viruses were sensitive to zanamivir and oseltamivir. All but one influenza A viruses tested (n=34) were resistant to amantadine (Table 2).
|Virus type and subtype||Oseltamivir||Zanamivir||Amantadine|
|# tested||# resistant (%)||# tested||# resistant (%)||# tested||# resistant (%)|
|A (H3N2)||34||0||34||0||34||33 (97.1%)|
|A (H1N1)||1||0||1||0||1||1 (100%)|
|B||8||0||8||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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