FluWatch report: October 28 to November 4, 2017 (week 44)
- Influenza activity continues to increase, but remained below the seasonal threshold in week 44.
- The percentage of laboratory tests positive for both influenza A and B is higher for this time of year compared to previous seasons. The majority of influenza detections continue to be A(H3N2).
- The number of influenza-related hospitalizations and regions reporting sporadic activity are above the expected levels for this time of year.
- For more information on the flu, see our Flu(influenza) web page.
On this page
- Influenza/ILI Activity (geographic spread)
- Laboratory Confirmed Influenza Detections
- Syndromic/Influenza-like Illness Surveillance
- Influenza Outbreak Surveillance
- Severe Outcomes Influenza Surveillance
- Influenza Strain Characterizations
- Antiviral Resistance
- Provincial and International Influenza Reports
- FluWatch definitions for the 2017-2018 season
Influenza/Influenza-like Illness Activity (geographic spread)
In week 44, one region in British Columbia reported localized activity, and 23 regions (British Columbia (2), Alberta (5), Saskatchewan (2), Ontario (5), Quebec (5), New Brunswick (2), Prince Edward Island (1) and Newfoundland and Labrador (1)) reported sporadic activity. Consistent with the increased number of influenza detections this season, a greater number of regions are reporting sporadic activity compared to previous seasons.
Figure 1 – Map of overall influenza/ILI activity level by province and territory, Canada, 2017-18, Week 44
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.
Laboratory Confirmed Influenza Detections
In week 44, the number of both influenza A and B detections increased, although the percentage of tests positive for influenza remained similar to the previous week at 4.5%, which is below the seasonal threshold. The number and percentage of both influenza A and B tests positive is higher for this time of year than was observed during the previous seven seasons. For data on other respiratory virus detections, see 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, 2017-18, weeks 35 to 44
The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the start and end of seasonal influenza activity.
To date this season, 900 laboratory-confirmed influenza detections have been reported, of which 88% have been influenza A. Influenza A(H3N2) has been the most common subtype detected this season, representing 94% of subtyped influenza A detections. 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 3 – Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, 2017-18, week 44
To date this season, detailed information on age and type/subtype has been received for 738 laboratory-confirmed influenza cases (Table 1). Among all influenza cases with reported age and type/subtype information, approximately one half of the cases have been reported in adults 65 years of age and older. This proportion was higher among cases of influenza A (52%) compared to influenza B (32%).
|Age groups (years)||Cumulative (August 27, 2017 to November 4, 2017)|
|Influenza A||B||Influenza A and B|
|A Total||A(H1) pdm09||A(H3)||A (UnS)Table 1 Footnote 1||Total||#||%|
Syndromic/Influenza-like Illness Surveillance
Healthcare Professionals Sentinel Syndromic Surveillance
In week 44, 1.6% of visits to healthcare professionals were due to influenza-like illness; a slight decrease compared to the previous week, but remains slightly above the 5-year average.
Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2017-18, weeks 35 to 44
Number of Sentinels Reporting in Week 44: 129
The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2012-13 to 2017-18
Participatory Syndromic Surveillance
FluWatchers is a participatory ILI surveillance system that relies on weekly voluntary submissions of syndromic information from Canadians across Canada.
In week 44, 1351 participants reported to FluWatchers, of which 1% reported symptoms of cough and fever in the preceding week and 20% of these consulted a healthcare professional. Among participants who reported cough and fever, 75% reported days missed from work or school, resulting in a combined total of 34 missed days.
|Number of Participants Reporting||Percentage participants reporting Cough and Fever||Percentage of participants with cough and fever who consulted a healthcare professional Facilities||Percentage of participants with cough and fever who reported missed days from work or school||Number of missed days from work or school|
Influenza Outbreak Surveillance
In week 44, one new laboratory-confirmed influenza outbreak was reported in a long-term care facility.
To date this season, 18 influenza/ILI outbreaks have been reported, of which 8 occurred in LTC facilities. Among the 12 outbreaks for which the influenza type/subtype was reported, 9 were associated with influenza A. The number of outbreaks to date is within the expected range for this time of year.
Figure 5 - Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, 2017-18, weeks 35 to 44
Severe Outcomes Influenza Surveillance
Provincial/Territorial Influenza Hospitalizations and Deaths
In week 44, 15 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote 1.
To date this season, 159 influenza-associated hospitalizations have been reported, 93% of which were associated with influenza A, and 115 cases (72%) were in adults 65 years of age or older. The number of cases is considerably elevated relative to this period in the previous two seasons. Eight ICU admissions and eight deaths have been reported.
Figure 6 - Cumulative numbers of hospitalizations by age-group reported by participating provinces and territories, 2017-18
- Footnote 1
Influenza-associated hospitalizations are reported by NL, PE, NS, NB, MB, AB, YT and NT. Only hospitalizations that require intensive medical care are reported by SK.
Pediatric Influenza Hospitalizations and Deaths
In week 44, one laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalization was reported by the Immunization Monitoring Program Active (IMPACT) network.
To date this season, 17 pediatric hospitalizations have been reported by the IMPACT network, 14 of which were associated with influenza A. Six ICU admissions and no deaths have been reported. The number of hospitalizations reported this season has been similar compared to the same period in recent seasons in which influenza A(H3N2) was the predominant circulating subtype (2014-15, 2016-17).
Figure 7 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, 2017-18 weeks 35-44
Figure 8 - Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, 2017-18 weeks 35-44
Influenza Strain Characterizations
During the 2017-18 influenza season, the National Microbiology Laboratory (NML) has characterized 52 influenza viruses [41 A(H3N2), 5 A(H1N1)pdm09 and 6 B viruses] that were received from Canadian laboratories.
Among influenza viruses characterized by hemagglutination inhibition assay during the 2017-18 season, all viruses were antigenically similar to the cell-culture propagated reference strains recommended by WHO.
|Strain Characterization Results||Count||Description|
|Influenza A (H3N2)|
|A/Hong Kong/4801/2014-like||7||Viruses antigenically similar to A/Hong Kong/4801/2014, the A(H3N2) component of the 2017-18 Northern Hemisphere's trivalent and quadrivalent vaccine.|
|Influenza A (H1N1)|
|A/Michigan/45/2015-like||5||Viruses antigenically similar to A/Michigan/45/2015, the A(H1N1) component of the 2017-18 Northern Hemisphere's trivalent and quadrivalent influenza vaccine.|
|1||Viruses antigenically similar to B/Brisbane/60/2008, the influenza B component of the 2017-18 Northern Hemisphere's trivalent and quadrivalent influenza vaccine. .|
|5||Viruses antigenically similar to B/Phuket/3073/2013, the additional influenza B component of the 2017-18 Northern Hemisphere quadrivalent influenza vaccine.|
Genetic Characterization of A(H3N2) viruses
During the 2017-18 season, 34 A(H3N2) viruses did not grow to sufficient titers for antigenic characterization by HI assay. Therefore, genetic characterization was performed to determine to which genetic group they belong. Sequence analysis showed that 24 H3N2 viruses belonged to genetic group 3C.2a and 10 viruses belonged to subclade 3C.2a1.
Additionally, of the seven influenza A(H3N2) viruses that were characterized antigenically as similar to A/Hong Kong/4801/2014, six belonged to genetic group 3C.2a and one virus belonged to subclade 3C.2a1.
A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A/H3N2 component of the 2017-18 Northern Hemisphere influenza vaccine.
During the 2017-18 season, the National Microbiology Laboratory (NML) has tested 50 influenza viruses for resistance to oseltamivir and zanamivir, and all viruses were sensitive (Table 4).
|Virus type and subtype||Oseltamivir||Zanamivir|
|# tested||# resistant (%)||# tested||# resistant (%)|
|A (H3N2)||39||0 (0%)||39||0 (0%)|
|A (H1N1)||5||0 (0%)||5||0 (0%)|
|B||6||0 (0%)||6||0 (0%)|
|TOTAL||50||0 (0%)||50||0 (0%)|
Note: Since the 2009 pandemic, all circulating influenza A viruses have been resistant to amantadine, and it is therefore not currently recommended for use in the treatment of influenza. During the 2017-18 season, the subset of influenza A viruses that were tested for resistance to amantadine were resistant.
Provincial and 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
- Alberta Health - Influenza Surveillance Report
- BC - Centre for Disease Control (BCCDC) - Influenza Surveillance
- New Brunswick - Influenza Surveillance Reports
- Newfoundland and Labrador - Surveillance and Disease Reports
- Nova Scotia - Flu Information
- Public Health Ontario - Ontario Respiratory Pathogen Bulletin
- Quebec - Système de surveillance de la grippe
- Manitoba - Epidemiology and Surveillance - Influenza Reports
- Saskatchewan - influenza Reports
- PEI - Influenza Summary
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