FluWatch report: April 3 to April 9, 2016 (week 14)

Overall Summary

  • Influenza activity peaked nationally in in the second week of March; however, lower but sustained activity is being reported throughout the country.
  • All regions of Canada reported sporadic or localized influenza activity.
  • Both influenza B and influenza A detections decreased in week 14. To date this season, a total of 34,105 positive influenza tests have been reported. 
  • Hospitalizations, ICU admissions and deaths among the pediatric population, while declining, remain above expected levels based on the past several influenza seasons.
  • Despite higher pediatric hospitalizations reported, the pediatric population account for the smallest proportion of all deaths reported.
  • 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

Download the alternative format
(PDF format, 869 KB, 9 pages)

Organization:
Date published: 2016-04-15

Influenza/Influenza-like Illness Activity (geographic spread)

In week 14, influenza activity was reported in 50 regions across Canada. A total of 30 regions reported sporadic activity levels, while the remaining 20 reported localized activity levels.

Figure 1. Map of overall influenza/ILI activity level by province and territory, Canada, week 14

Figure 1
Figure 1 Legend

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

In week 14, influenza activity was reported in 50 regions across Canada. A total of 30 regions reported sporadic activity levels, while the remaining 20 reported localized activity levels.

Laboratory Confirmed Influenza Detections

In week 14, the percentage of tests positive for influenza continued to decrease from the previous week [from 28% in week 13 to 23% in week 14] (Figure 2). Compared to the previous five seasons, the percent positive (23%) reported in week 14 was above the five year average for that week and exceeded the expected levels (range 11.1%-16.7%). With the late start to the 2015-16 influenza season, these elevated levels are not unexpected.

Figure 2. Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2015-16

Figure 2
Figure 2 - Text Description

In week 14, the percentage of tests positive for influenza continued to decrease from the previous week [from 28% in week 13 to 23% in week 14].

In week 14, there were 1,914 positive influenza tests reported. The number of positive influenza B tests accounted for an increasing proportion of all positive influenza tests reported. Both influenza B and influenza A detections decreased in week 14. This week, influenza B accounted for 41% of all positive tests. To date, 79% of influenza detections have been influenza A and among those subtyped, the vast majority have been influenza A(H1N1) [91% (10510/11511)].

Figure 3. Cumulative numbers of positive influenza specimens by type/subtype and province, Canada, 2015-16

Figure 3

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
Reporting
provincesTable Figure 3 - Footnote 1
Weekly (April 3 to April 9, 2016) Cumulative (August 30, 2015 to April 9, 2016)
Influenza A B Influenza A B A & B
Total
A
Total
A
(H1)pdm09
A
(H3)
A Table Figure 3 - Footnote UnS B
Total
A
Total
A
(H1)pdm09
A
(H3)
ATable Figure 3 - Footnote UnS B
Total
Table Figure 3 - Footnote 1

Specimens from NT, YT, and NU are sent to reference laboratories in other provinces. Cumulative data includes updates to previous weeks.

Return to Table Figure 3 - Footnote 1 referrer

Table Figure 3 - Footnote 2

Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections.

Return to Table Figure 3 - Footnote 2 referrer

Table Figure 3 - Footnote UnS

Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available.

Return to first Table Figure 3 - Footnote UnS referrer

Table Figure 3 - Footnote x

Suppressed to prevent residual disclosure.

Return to first Table Figure 3 - Footnote x referrer

BC 166 105 11 50 29 1912 910 346 656 1095 2930
AB 72 42 <5 Table Figure 3 - Footnote x 87 3863 3552 174 137 1415 5278
SK 28 19 <5 Table Figure 3 - Footnote x 48 2902 1467 46 737 652 3554
MB 14 5 <5 Table Figure 3 - Footnote x 22 855 175 37 643 125 980
ON 237 75 10 152 202 7218 3116 353 3749 1945 9163
QC 404 39 0 365 376 8328 969 5 7354 1843 10171
NB 165 11 0 154 11 899 75 3 821 43 942
NS 33 0 0 33 <5 270 Table Figure 3 - Footnote x <5 269 7 277
PE 6 <5 <5 Table Figure 3 - Footnote x 0 57 52 5 0 0 57
NL 0 0 0 0 0 408 58 <5 Table Figure 3 - Footnote x 14 422
YT 6 <5 Table Figure 3 - Footnote x <5 0 77 45 <5 Table Figure 3 - Footnote x 19 96
NT 1 <5 0 Table Figure 3 - Footnote x <5 120 90 25 5 8 128
NU 3 0 0 3 0 16 <5 Table Figure 3 - Footnote x 15 14 30
Canada 1135 302 28 805 779 26925 10510 1001 14762 7180 34105
Percentage Table Figure 3 - Footnote 2 59% 27% 2% 71% 41% 79% 39% 4% 55% 21% 100%

To date this season, detailed information on age and type/subtype has been received for 28,818 cases. Children and teenagers (0-19 years of age) accounted for one third of all influenza cases (33%). Children (0-19), young adults (20-44) and middle-aged adults (45-64) accounted for approximately an equal proportion of influenza A(H1N1) cases (28%).

Table 1. Weekly and cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reporting Table 1 - Footnote 1, Canada, 2015-16
Age groups (years) Weekly (April 3 to April 9, 2016) Cumulative (August 30, 2015 to April 9, 2016)
Influenza A B Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) A UnSTable 1 - Footnote 3 Total A Total A(H1) pdm09 A(H3) A UnSTable 1 - Footnote 3 Total # %
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 - Footnote 1 referrer

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 - Footnote 2 referrer

Table 1 - Footnote 3

Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available.

Return to first Table 1 - Footnote 3 referrer

Table 1 - Footnote x

Suppressed to prevent residual disclosure.

Return to first Table 1 - Footnote x referrer

<5 125 15 0 110 124 4287 1674 63 2550 1044 5333 19%
5-19 46 7 <5 Table 1 - Footnote x 138 2302 997 95 1210 1832 4136 14%
20-44 118 30 <5 Table 1 - Footnote x 120 5566 2655 150 2761 1574 7140 25%
45-64 171 37 <5 Table 1 - Footnote x 75 5994 2639 178 3177 763 6757 23%
65+ 175 31 6 138 100 4477 1506 396 2575 974 5452 19%
Total 635 120 10 505 557 22626 9471 882 12273 6187 28818 100%
PercentageTable 1 - Footnote 2 53% 19% 2% 80% 47% 79% 42% 4% 54% 21%    

For 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 decreased from the previous week from 45.2 per 1,000 patient visits in week 13, to 26.8 per 1,000 patient visits in week 14. The highest ILI consultation rate was found in the 0-4 years age group (55.9 per 1,000) and the lowest was found in the ≥65 years age group (5.5 per 1,000) (Figure 4).

Figure 4. Influenza-like-illness (ILI) consultation rates by age group and week, Canada, 2015-16

Figure 4

Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data are compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.

Figure 4 - Text Description

Influenza-like illness consultation rate by age-group in week 14 for the 2015-16 season:
Age 0-4: 55.9; Age 5-19: 40.9; Age 20-64: 24.1; Age 65+: 5.5

Pharmacy Surveillance

During week 14, the proportion of prescriptions for antivirals dereaesd to 50.4 antiviral prescriptions per 100,000 total prescriptions, which is lower than the five year historical average for week 14. The proportion of prescriptions for antivirals remains highest among children. In week 14, the proportion reported among children was 102.4 per 100,000 total prescriptions.

Figure 5. Proportion of prescription sales for influenza antivirals by age group and week, Canada, 2015-16

Figure 5

Note: Pharmacy sales data are provided to the Public Health Agency of Canada by Rx Canada Inc. and sourced from major retail drug chains representing over 3,000 stores nationwide (excluding Nunavut) in 85% of Health Regions. Data provided include the number of new antiviral prescriptions (for Tamiflu[oseltamivir] and Relenza [zanamivir]) and the total number of new prescriptions dispensed by Province/Territory and age group.

* The average weekly proportion includes data from April 2011 to March 2015.

Figure 5 - Text Description

Proportion of antiviral prescriptions per 100,000 total prescriptions
Average National Rate (Yrs 10-11 to 14-15): 65.4.; Rate wk 14: 100.8
Proportion of antiviral prescriptions by age-group in week 14 for the 2015-16 season:
Infant: 71.6; child: 102.4; adult: 43.1; senior: 55.4

Influenza Outbreak Surveillance

In week 14, 17 new laboratory confirmed influenza outbreaks were reported: 14 in long-term care facilities (LTCF), two in hospitals and one in institutions or community settings. Of the outbreaks with known strains or subtypes,  three outbreaks were due to influenza B, one outbreak was due to influenza A(H1N1), two outbreaks were due to influenza A(H3N2) and eight were due to influenza A(UnS). Additionally, three ILI outbreaks were reported schools.

To date this season, 374 outbreaks have been reported. At week 14 in the 2014-15 season, 1646 outbreaks were reported and in the 2013-14 season,198 outbreaks were reported.

Figure 6. Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote 1 by report week, Canada, 2015-2016

Figure 6
Figure 6 - Text Description
Report week Hospitals Long Term Care Facilities Other
35 0 0 0
36 0 0 0
37 1 1 0
38 0 0 0
39 0 2 0
40 0 2 1
41 0 0 0
42 0 0 0
43 0 1 0
44 1 3 1
45 1 1 0
46 0 0 0
47 0 0 0
48 0 1 0
49 0 1 0
50 0 2 0
51 1 1 0
52 1 0 2
1 0 2 1
2 0 2 0
3 1 4 1
4 4 6 3
5 8 6 3
6 8 10 3
7 2 17 8
8 6 27 7
9 13 24 8
10 9 23 14
11 2 21 4
12 9 15 5
13 5 12 4
14 2 14 1

Sentinel Pediatric Hospital Influenza Surveillance

Paediatric Influenza Hospitalizations and Deaths

Hospitalizations reported by the the Immunization Monitoring Program Active (IMPACT) network continue to decrease (Figure 7). In week 14, 58 hospitalizations were reported. The largest proportion of hospitalizations were in children aged 2-4 years, accounting for 46.5% of the hospitalizations. For the first time this season, more influenza B cases were reported than influenza A cases (31 vs. 27 respectively).

To date this season, 1,138 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations have been reported by  the IMPACT network: 853 hospitalized cases (75%) were due to influenza A and 285 cases (25%) were due to influenza B. The greatest proportion of hospitalized cases were in children aged 0-2 years (40 %). To date,190 intensive care unit (ICU) admissions have been reported. Children aged 2 to 4 and 5 to 9 years accounted for 28% and 26% respectively of ICU admissions. A total of 113 ICU cases (59%) reported at least one underlying condition or comorbidity. Eight influenza-associated deaths have been reported.

Table 2 - Cumulative numbers of peadiatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, Canada, 2015-16
Age Groups Cumulative (30 Aug. 2015 to 9 April 2016)
Influenza A Influenza B Influenza A and B (#(%))
A Total A(H1) pdm09 A(H3) A (UnS) B Total
Table 2 - Footnote x

Suppressed to prevent residual disclosure.

Return to first Table 2 - Footnote x referrer

0-5m 112 32 5 75 21 133 (12%)
6-23m 261 73 7 181 59 320 (28%)
2-4y 246 78 <5 Table 2 - Footnote x 78 324 (28%)
5-9y 177 47 <5 Table 2 - Footnote x 89 266 (23%)
10-16y 57 18 <5 Table 2 - Footnote x 38 95 (8%)
Total 853 248 21 584 285 1138 (100%)

Figure 7. Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2015-16, paediatric and adult hospitalizations (≤16 years of age, IMPACT; ≥16 years of age, CIRN-SOS)

Figure 7

Not included in Table 2 and Figure 7 are two IMPACT cases that were due to co-infections of influenza A and B.

Figure 7 - Text Description
Report week IMPACT CIRN-SOS
35 0 0
36 0 0
37 1 0
38 2 0
39 0 0
40 0 0
41 1 0
42 0 0
43 1 0
44 0 2
45 2 0
46 1 3
47 2 1
48 2 1
49 3 7
50 3 3
51 6 6
52 13 11
1 20 19
2 13 13
3 24 26
4 39 21
5 48 44
6 78 53
7 108 90
8 148 125
9 147 103
10 148 123
11 114 112
12 90 80
13 66 79
14 58 36

Adult Influenza Hospitalizations and Deaths

In week 14, 36 hospitalizations were reported by the Canadian Immunization Research Network Serious Outcome Surveillance (CIRN-SOS) (Figure 7). The largest proportion of hospitalizations was in adults 65+ years of age (50%) and due to influenza A (75%).

To date this season, 956 laboratory-confirmed influenza-associated adult (≥16 years of age) hospitalizations have been reported by CIRN-SOS (Table 3). The majority of hospitalized cases were due to influenza A (85%) and the largest reported proportion was among adults ≥65 years of age (49%). One hundred and thirty-seven intensive care unit (ICU) admissions have been reported. A total of 88 ICU cases reported at least one underlying condition or comorbidity. A total of 38 deaths have been reported this season with the majority of deaths reported in adults ≥65 years of age (63%).

Table 3 - Cumulative numbers of adult hospitalizations (≥16 years of age) with influenza reported by the CIRN-SOS network, Canada, 2015-16
Age groups (years) Cumulative (1 Nov. 2015 to 9 April 2016)
Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) A(UnS) Total # (%)
Table 3 - Footnote x

Suppressed to prevent residual disclosure.

Return to first Table 3 - Footnote x referrer

16-20 5 <5 0 <5 <5 6 (1%)
20-44 127 38 <5 Table 3 - Footnote x 28 155 (16%)
45-64 286 84 3 199 30 316 (33%)
65+ 388 96 21 271 84 472 (49%)
Unknown 6 0 <5 <5 <5 7 (1%)
Total 812 225 26 561 144 956
% 85% 28% 3% 69% 15% 100%

Figure 8. Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group (≥16 year of age), Canada 2015-16

Figure 8

Note: The number of hospitalizations reported through CIRN-SOS and IMPACT represents a subset of all influenza-associated adult and paediatric hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.

x - Suppressed to prevent residual disclosure.

Figure 8 - Text Description
Age-group (years) Hospitalizations (n=949) ICU admissions (n=137) Deaths (n=38)
Table Figure 8 - Footnote x

Suppressed to prevent residual disclosure.

Return to first Table Figure 8 - Fo2tn273x referrer

16-20 0.6% Table Figure 8 - Footnote x% Table Figure 8 - Footnote x%
20-44 16.3% Table Figure 8 - Footnote x% Table Figure 8 - Footnote x%
45-64 33.3% 43.1% 31.6%
65+ 49.7% 34.3% 63.2%

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 14, 311 hospitalizations were reported by participating provinces and territoriesFootnote *. The majority of hospitalizations were due to influenza A (61%), however a marked increase in the proportion of influenza B cases has been noted in week 14. Influenza B accounted for 39% of all  influenza hospitalizations in week 14 compared to 22% in week 13. The largest proportion of cases reported in week 14 was in adults 65+ years of age (35%).

Since the start of the 2015-16 season, 4,371 laboratory-confirmed influenza-associated hospitalizations have been reported. A total of 3,637 hospitalizations (83%) were due to influenza A and 734 (17%) were due to influenza B. Of the 473 ICU admissions reported, 245 (58%) were due to influenza A(H1N1) A total of 193 deaths have been reported; all but 22 were associated with influenza A.

Overall this season, hospitalizations have been reported more frequently among adults ≥65 years of age. The largest proportion of ICU admissions were reported in adults 45-64 years of age and the highest proportion of fatal cases was reported in adults ≥65 years of age. Pediatric (0-19 years) and young to middle-aged adults (20-44 years) accounted for 42% of all hospitalizations and 15% of all deaths reported to date this season.

Figure 9. Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada 2015-16

Figure 9
Figure 9 - Text Description
Age-group (years) Hospitalizations (n=4371) ICU admissions (n=473) Deaths (n=193)
0-4 19.3% 8.9% 2.6%
5-19 9.2% 5.9% 3.1%
20-44 13.5% 18.2% 9.3%
45-64 27.1% 45.2% 37.3%
65+ 30.9% 21.8% 47.7%

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 1580 influenza viruses [179 A(H3N2), 889 A(H1N1) and 512 influenza B].

Influenza A (H3N2): When tested by hemagglutination inhibition (HI) assays, 42 A(H3N2) viruses  were antigenically characterized as A/Switzerland/9715293/2013-like using antiserum raised against cell-propagated A/Switzerland/9715293/2013.  

Sequence analysis was done on 137 A(H3N2) viruses. All 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): All of the 889 A(H1N1) viruses characterized were antigenically similar to A/California/7/2009, the A(H1N1) component of the 2015-16 influenza vaccine.

Influenza B: A total of 125 influenza B viruses characterized  were antigenically similar to the vaccine strain B/Phuket/3073/2013. A total of 387 influenza B viruses were 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 A/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  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.

Antiviral Resistance

During the 2015-16 season, the National Microbiology Laboratory (NML) has tested 1,078 influenza viruses for resistance to oseltamivir, 1,079 for resistance to zanamivir and 1,027 influenza viruses for resistance to amantadine. All but eight tested viruses were sensitive to oseltamivir. The eight H1N1 viruses resistant to oseltamivir had a H275Y mutation. All viruses tested for resistance were sensitive to zanamivir.  All but one influenza A viruses were resistant to amantadine (Table 4).

Table 4. Antiviral resistance by influenza virus type and subtype, Canada, 2015-16
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
Table 4 - Footnote *

NA - not applicable

Return to first Table 4 - Footnote * referrer

A (H3N2) 142 0 (0%) 142 0 (0%) 173 172 (99.4%)
A (H1N1) 656 8 (1.2%) 657 0 (0%) 854 854 (100%)
B 280 0 (0%) 280 0 (0%) NATable 4 - Footnote * NATable 4 - Footnote *
Total 1078 8 (0.7%) 1079 0 (0%) 1027 1026

International Influenza Reports


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.

ILI/Influenza outbreaks

Schools:
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.
Workplace:
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:

  1. evidence of increased ILIFootnote * and
  2. lab confirmed influenza detection(s) together with
  3. outbreaks in schools, hospitals, residential institutions and/or other types of facilities occurring in less than 50% of the influenza surveillance regionFootnote

4 = Widespread:

  1. evidence of increased ILIFootnote * and
  2. lab confirmed influenza detection(s) together with
  3. outbreaks in schools, hospitals, residential institutions and/or other types of facilities occurring in greater than or equal to 50% of the influenza surveillance regionFootnote

Note: ILI data may be reported through sentinel physicians, emergency room visits or health line telephone calls.

Report a problem or mistake on this page
Please select all that apply:

Thank you for your help!

You will not receive a reply. For enquiries, contact us.

Date modified: