FluWatch report: April 8 to April 14, 2018 (week 15)
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Organization:
Public Health Agency of Canada
Date published: 2018-04-13
Related Topics
Overall Summary
On this page
In week 15, one region in QC reported widespread activity and 23 regions (BC(1), AB(1), MB(2), ON(7), QC(3), NB(2), NL(3), NS(2), PE(1) and NT(1)) reported localized activity.
Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, week 2018-15
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
In week 15, the overall percentage of tests positive for influenza was 15%, a decrease from the previous week. Overall, laboratory detections of influenza are steadily decreasing. Influenza A accounted for 54% of influenza detections in week 15.
Overall, laboratory detections of influenza are around the average for this time of year. 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, weeks 2017-35 to 2018-15
The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the period of seasonal influenza activity.
Figure 2 - Text Description To date this season, 62,062 laboratory-confirmed influenza detections have been reported, of which 56% have been influenza A. Influenza A(H3N2) has been the most common subtype detected this season, representing 91% 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, weeks 2017-35 to 2018-15
Figure 3 - Text Description To date this season, detailed information on age and type/subtype has been received for 50,204 laboratory-confirmed influenza cases (Table 1). Adults 65 years of age and older represent the largest proportion of cases overall (50%), and among cases of influenza A(H3N2) (59%) and influenza B (48%). Adults aged 20-64 represent 32% of cases overall and 29% of influenza A(H3N2) and 34% of influenza B cases. Although much smaller in numbers (883), the majority of influenza A(H1N1)pdm09 cases are among adults less than 65 years of age, with adults aged 20-64 and children 0-19 years accounting for 54% and 31% of cases respectively.
Syndromic/Influenza-like Illness Surveillance
Healthcare Practitioners Sentinel Syndromic Surveillance
In week 15, 1.5% of visits to healthcare professionals were due to influenza-like illness (ILI); a decrease from the previous week.
Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2017-35 to 2018-15
Number of Sentinels Reporting in Week 15: 159
The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2012-13 to 2016-17
Figure 4 - Text Description 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 15, 1,315 participants reported to FluWatchers, of which 2% reported symptoms of cough and fever, and 41% of these consulted a healthcare professional. Among participants who reported cough and fever, 73% reported days missed from work or school, resulting in a combined total of 59 missed days of work or school.
Influenza Outbreak Surveillance
In week 15, 44 laboratory-confirmed outbreaks of influenza were reported. Among the reported influenza outbreaks, 31 were reported in long-term care facilities (LTC), three in hospitals, and 10 in other settings. In addition, two ILI outbreaks were reported in schools. Among the 35 outbreaks with influenza type/subtype reported, 22 (63%) were associated with influenza A, 12 (34%) were associated with influenza B and one outbreak (3%) was associated with a mix of influenza A and B.
To date this season, 1,751 influenza/ILI outbreaks have been reported, of which 1,081 (62%) occurred in LTC facilities. Among the 1,500 outbreaks for which the influenza type/subtype was reported, 825 (55%) were associated with influenza A and 606 (40%) were associated with influenza B, and 69 (5%) were associated with a mix of A and B.
Figure 5 - Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2017-35 to 2018-15
Figure 5 - Text Description Severe Outcomes Influenza Surveillance
Provincial/Territorial Influenza Hospitalizations and Deaths
To date this season, 4,835 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote1. Among the hospitalizations, 3,260 (67%) were associated with influenza A, and 3,190 cases (66%) were in adults 65 years of age or older.
Additionally, 487 ICU admissions and 265 deaths have been reported to date. Adults aged 65 years of age or older accounted for the greatest proportion of ICU cases (44%), followed by adults aged 20-64 (39%). Adults aged 65 years of age or older accounted the majority of deaths (85%).
Figure 6 - Cumulative numbers of hospitalizations by age-group reported by participating provinces and territoriesfigure 6 note1, weeks 2017-35 to 2018-15
Figure 6 - Text Description Figure 6 note 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.
Return to figure 6 note1referrer
Pediatric Influenza Hospitalizations and Deaths
In week 15, 12 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. Influenza A accounted for 67% of the hospitalizations. Pediatric hospitalizations have been on a general decline since week 07. The number of weekly reported hospitalizations has finally fallen to levels that are near the seven-season average.
To date this season, 1,034 pediatric hospitalizations have been reported by the IMPACT network, 643 (62%) of which were associated with influenza A. Children 0-23 months accounted for the largest proportion of influenza A hospitalizations (40%). Among the 391 hospitalizations due to influenza B, children 5-9 years accounted for the largest proportion of cases (31%).
Additionally, 175 ICU admissions and nine deaths have been reported to date. Children aged 0-23 months accounted for the greatest proportion of ICU cases (29%), followed by children aged 5-9 years (26%). Among the ICU cases with available information, 63% were due to influenza A and approximately 47% had no reported previous or concurrent medical conditions. All but one reported deaths were among children over the age of two.
Figure 7 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, weeks 2017-35 to 2018-15
Figure 7 - Text Description Figure 8 - Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, weeks 2017-35 to 2018-15
Figure 8 - Text Description Figure 8 Footnote 1 The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2016-17
Return to figure 8 note1referrer
Influenza Strain Characterizations
During the 2017-18 influenza season, the National Microbiology Laboratory (NML) has characterized 3,146 influenza viruses [1,377 A(H3N2), 239 A(H1N1)pdm09 and 1,530 B viruses] that were received from Canadian laboratories.
Antigenic Characterization
Among influenza viruses characterized by hemagglutination inhibition (HI) assay during the 2017-18 season, most viruses were antigenically similar to the cell-culture propagated reference strains recommended by WHO.
Genetic Characterization of A(H3N2) viruses
During the 2017-18 season, 1,021 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 913 A(H3N2) viruses belonged to genetic group 3C.2a, 106 viruses belonged to subclade 3C.2a1 and two viruses belonged to the clade 3C.3a.
Additionally, of the 356 influenza A(H3N2) viruses that were characterized antigenically as similar to A/Hong Kong/4801/2014, 245 belonged to genetic group 3C.2a and 25 viruses belonged to subclade 3C.2a1. The 79 viruses that showed reduced titer to A/Hong Kong/4801/2014 belonged to genetic clade 3C.3a. Sequencing is pending for the remaining seven isolates.
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.
Genetic Characterization of Influenza B viruses
Among the viruses characterized antigenically as having reduced titer to ferret antisera produced against cell-propagated B/Brisbane/60/2008, sequence analysis showed that 47 viruses had a two amino acid deletion in the HA gene. Sequencing is pending for the remaining virus isolate.
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Download the alternative format
(PDF format, 563 KB, 10 pages)
Organization:
Public Health Agency of Canada
Date published: 2018-04-13
Related Topics
Overall Summary
- Overall influenza activity in Canada continued to decrease, but many parts of the country are still reporting localized activity.
- Two indicators of influenza activity (influenza-like illness and outbreaks) slightly increased from the previous week.
- Detections of influenza A were greater than those of influenza B.
- To date this season, the majority of laboratory-confirmed cases, hospitalizations and deaths with influenza have been among adults 65 years of age and older.
- 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 Surveillance System Description and Definitions, 2017-18
In week 15, one region in QC reported widespread activity and 23 regions (BC(1), AB(1), MB(2), ON(7), QC(3), NB(2), NL(3), NS(2), PE(1) and NT(1)) reported localized activity.
Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, week 2018-15
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
In week 15, the overall percentage of tests positive for influenza was 15%, a decrease from the previous week. Overall, laboratory detections of influenza are steadily decreasing. Influenza A accounted for 54% of influenza detections in week 15.
Overall, laboratory detections of influenza are around the average for this time of year. 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, weeks 2017-35 to 2018-15
The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the period of seasonal influenza activity.
Figure 2 - Text Description To date this season, 62,062 laboratory-confirmed influenza detections have been reported, of which 56% have been influenza A. Influenza A(H3N2) has been the most common subtype detected this season, representing 91% 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, weeks 2017-35 to 2018-15
Figure 3 - Text Description To date this season, detailed information on age and type/subtype has been received for 50,204 laboratory-confirmed influenza cases (Table 1). Adults 65 years of age and older represent the largest proportion of cases overall (50%), and among cases of influenza A(H3N2) (59%) and influenza B (48%). Adults aged 20-64 represent 32% of cases overall and 29% of influenza A(H3N2) and 34% of influenza B cases. Although much smaller in numbers (883), the majority of influenza A(H1N1)pdm09 cases are among adults less than 65 years of age, with adults aged 20-64 and children 0-19 years accounting for 54% and 31% of cases respectively.
0-4 | 3077 | 144 | 551 | 2382 | 1452 | 4529 | 9% |
5-19 | 2256 | 126 | 536 | 1594 | 2525 | 4781 | 10% |
20-44 | 4150 | 244 | 1179 | 2727 | 2707 | 6857 | 14% |
45-64 | 4558 | 229 | 1427 | 2902 | 4571 | 9129 | 18% |
65+ | 14610 | 140 | 5314 | 9156 | 10298 | 24908 | 50% |
Total | 28651 | 883 | 9007 | 18761 | 21553 | 50204 | 100% |
Healthcare Practitioners Sentinel Syndromic Surveillance
In week 15, 1.5% of visits to healthcare professionals were due to influenza-like illness (ILI); a decrease from the previous week.
Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2017-35 to 2018-15
Number of Sentinels Reporting in Week 15: 159
The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2012-13 to 2016-17
Figure 4 - Text Description 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 15, 1,315 participants reported to FluWatchers, of which 2% reported symptoms of cough and fever, and 41% of these consulted a healthcare professional. Among participants who reported cough and fever, 73% reported days missed from work or school, resulting in a combined total of 59 missed days of work or school.
1315 | 2% | 41% | 73% | 59 |
In week 15, 44 laboratory-confirmed outbreaks of influenza were reported. Among the reported influenza outbreaks, 31 were reported in long-term care facilities (LTC), three in hospitals, and 10 in other settings. In addition, two ILI outbreaks were reported in schools. Among the 35 outbreaks with influenza type/subtype reported, 22 (63%) were associated with influenza A, 12 (34%) were associated with influenza B and one outbreak (3%) was associated with a mix of influenza A and B.
To date this season, 1,751 influenza/ILI outbreaks have been reported, of which 1,081 (62%) occurred in LTC facilities. Among the 1,500 outbreaks for which the influenza type/subtype was reported, 825 (55%) were associated with influenza A and 606 (40%) were associated with influenza B, and 69 (5%) were associated with a mix of A and B.
Figure 5 - Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2017-35 to 2018-15
Figure 5 - Text Description Severe Outcomes Influenza Surveillance
Provincial/Territorial Influenza Hospitalizations and Deaths
To date this season, 4,835 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote1. Among the hospitalizations, 3,260 (67%) were associated with influenza A, and 3,190 cases (66%) were in adults 65 years of age or older.
Additionally, 487 ICU admissions and 265 deaths have been reported to date. Adults aged 65 years of age or older accounted for the greatest proportion of ICU cases (44%), followed by adults aged 20-64 (39%). Adults aged 65 years of age or older accounted the majority of deaths (85%).
Figure 6 - Cumulative numbers of hospitalizations by age-group reported by participating provinces and territoriesfigure 6 note1, weeks 2017-35 to 2018-15
Figure 6 - Text Description Figure 6 note 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.
Return to figure 6 note1referrer
Pediatric Influenza Hospitalizations and Deaths
In week 15, 12 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. Influenza A accounted for 67% of the hospitalizations. Pediatric hospitalizations have been on a general decline since week 07. The number of weekly reported hospitalizations has finally fallen to levels that are near the seven-season average.
To date this season, 1,034 pediatric hospitalizations have been reported by the IMPACT network, 643 (62%) of which were associated with influenza A. Children 0-23 months accounted for the largest proportion of influenza A hospitalizations (40%). Among the 391 hospitalizations due to influenza B, children 5-9 years accounted for the largest proportion of cases (31%).
Additionally, 175 ICU admissions and nine deaths have been reported to date. Children aged 0-23 months accounted for the greatest proportion of ICU cases (29%), followed by children aged 5-9 years (26%). Among the ICU cases with available information, 63% were due to influenza A and approximately 47% had no reported previous or concurrent medical conditions. All but one reported deaths were among children over the age of two.
Figure 7 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, weeks 2017-35 to 2018-15
Figure 7 - Text Description Figure 8 - Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, weeks 2017-35 to 2018-15
Figure 8 - Text Description Figure 8 Footnote 1 The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2016-17
Return to figure 8 note1referrer
Influenza Strain Characterizations
During the 2017-18 influenza season, the National Microbiology Laboratory (NML) has characterized 3,146 influenza viruses [1,377 A(H3N2), 239 A(H1N1)pdm09 and 1,530 B viruses] that were received from Canadian laboratories.
Antigenic Characterization
Among influenza viruses characterized by hemagglutination inhibition (HI) assay during the 2017-18 season, most viruses were antigenically similar to the cell-culture propagated reference strains recommended by WHO.
A/Hong Kong/4801/2014-like | 277 | Viruses antigenically similar to A/Hong Kong/4801/2014, the A(H3N2) component of the 2017-18 Northern Hemisphere's trivalent and quadrivalent vaccine. |
Reduced titer to A/Hong Kong/4801/2014 | 79 | These A(H3N2) viruses reacted poorly with antisera raised against cell-propagated A/Hong Kong/4801/2014, suggesting some antigenic differences |
A/Michigan/45/2015-like | 239 | Viruses antigenically similar to A/Michigan/45/2015, the A(H1N1)pdm09 component of the 2017-18 Northern Hemisphere's trivalent and quadrivalent influenza vaccine. |
B/Brisbane/60/2008-like (Victoria lineage) | 16 | Viruses antigenically similar to B/Brisbane/60/2008. B/Brisbane/60/2008 is the influenza B component of the 2017-18 Northern Hemisphere's trivalent and quadrivalent influenza vaccine. |
Reduced titer to B/Brisbane/60/2008 (Victoria lineage) |
48 | These B/Victoria lineage viruses reacted poorly with antisera raised against cell-propagated B/Brisbane/60/2008, suggesting some antigenic differences. |
B/Phuket/3073/2013-like (Yamagata lineage) |
1,466 | Viruses antigenically similar to B/Phuket/3073/2013, the additional influenza B component of the 2017-18 Northern Hemisphere quadrivalent influenza vaccine. |
During the 2017-18 season, 1,021 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 913 A(H3N2) viruses belonged to genetic group 3C.2a, 106 viruses belonged to subclade 3C.2a1 and two viruses belonged to the clade 3C.3a.
Additionally, of the 356 influenza A(H3N2) viruses that were characterized antigenically as similar to A/Hong Kong/4801/2014, 245 belonged to genetic group 3C.2a and 25 viruses belonged to subclade 3C.2a1. The 79 viruses that showed reduced titer to A/Hong Kong/4801/2014 belonged to genetic clade 3C.3a. Sequencing is pending for the remaining seven isolates.
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.
Genetic Characterization of Influenza B viruses
Among the viruses characterized antigenically as having reduced titer to ferret antisera produced against cell-propagated B/Brisbane/60/2008, sequence analysis showed that 47 viruses had a two amino acid deletion in the HA gene. Sequencing is pending for the remaining virus isolate.
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