FluWatch report: November 6 to November 12, 2016 (week 45)

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Organization: Public Health Agency of Canada

Date published: 2016-11-18

  • Influenza activity is at interseasonal levels with the majority regions in Canada reporting no activity.
  • A total of 181 positive influenza detections were reported in week 45. Influenza A(H3N2) continues to be the most common subtype detected.
  • In week 45, 1.6% of visits to sentinel healthcare professionals were due to influenza-like symptoms, a slight increase from week 44.
  • Two laboratory-confirmed influenza outbreaks were reported in week 45, a decrease from the previous week.
  • Sixteen hospitalizations were reported from participating Provinces and Territories in week 45; all due to influenza A. Less than five ICU admissions have been reported in week 45.
  • To date, the majority of pediatric hospitalizations reported were due to Influenza A(H3N2).
  • For more information on the flu, see our Flu(influenza) web page.

In week 45, a total of 29 regions reported no influenza activity. Sporadic influenza activity was reported in 18 regions across seven provinces (BC, AB, SK, MB, ON,QC and NL). Localized activity was reported in six regions across four provinces/territories (YK, BC, AB and ON). For more details on a specific region, click on the map.

Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, Week 45
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 45, a total of 29 regions reported no influenza activity. Sporadic influenza activity was reported in 18 regions across seven provinces (BC, AB, SK, MB, ON,QC and NL). Localized activity was reported in six regions across four provinces/territories (YK, BC, AB and ON).

The percentage of tests positive for influenza increased in week 45 but remained at interseasonal levels, with 4.4% of tests positive for influenza. For data on other respiratory virus detections, see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada (PHAC) website.

Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2016-17
Figure 2
Figure 2 - Text Description
Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2016-17
Report Week A(Unsubtyped) A(H3) A(H1)pdm09 Influenza B
35 0 <5 0 0
36 <5 0 <5 9
37 <5 17 0 <5
38 11 28 <5 <5
39 14 41 <5 7
40 0 47 <5 <5
41 10 31 0 <5
42 14 49 <5 6
43 16 76 <5 <5
44 23 106 <5 9
45 68 108 <5 11
46 0 0 0 0
47 0 0 0 0
48 0 0 0 0
49 0 0 0 0
50 0 0 0 0
51 0 0 0 0
52 0 0 0 0
1 0 0 0 0
2 0 0 0 0
3 0 0 0 0
4 0 0 0 0
5 0 0 0 0
6 0 0 0 0
7 0 0 0 0
8 0 0 0 0
9 0 0 0 0
10 0 0 0 0
11 0 0 0 0
12 0 0 0 0
13 0 0 0 0
14 0 0 0 0
15 0 0 0 0
16 0 0 0 0
17 0 0 0 0
18 0 0 0 0
19 0 0 0 0
20 0 0 0 0
21 0 0 0 0
22 0 0 0 0
23 0 0 0 0
24 0 0 0 0
25 0 0 0 0
26 0 0 0 0
27 0 0 0 0
28 0 0 0 0
29 0 0 0 0
30 0 0 0 0
31 0 0 0 0
32 0 0 0 0
33 0 0 0 0
34 0 0 0 0

Nationally in week 45, there were 181 positive influenza tests. Influenza A(H3N2) was the most common subtype detected. BC, AB and ON accounted for the majority (81%) of influenza detections in week 45. To date, influenza A(H3N2) is the most common subtype detected, representing 63% of laboratory-confirmed 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, 2016-17
Figure 3
Figure 3 - Text Description
Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, 2016-17
Reporting
provincesTable Figure 3 - Footnote 1
Weekly (October 30, 2016 to November 5, 2016) Cumulative (August 28, 2016 to November 5, 2016)
Influenza A B Influenza A B A & B
Total
A
Total
A
(H1)pdm09
A
(H3)
ATable Figure 3 - Footnote UnS B
Total
A
Total
A
(H1)pdm09
A
(H3)
ATable Figure 3 - Footnote UnS B
Total
BC 46 0 46 0 2 214 2 211 1 10 224
AB 63 0 38 25 3 201 2 170 29 13 214
SK 0 0 0 0 0 0 0 0 0 0 0
MB 1 0 1 0 0 9 0 9 0 1 10
ON 38 2 16 20 2 134 7 80 47 15 149
QC 17 0 3 14 2 56 0 4 52 9 65
NB 1 0 0 1 0 4 0 2 2 0 4
NS 1 0 0 1 0 4 0 1 3 0 4
PE 0 0 0 0 0 1 0 1 0 0 1
NL 0 0 0 0 0 1 0 1 0 1 2
YT 5 0 4 1 0 29 0 28 1 0 29
NT 0 0 0 0 0 0 0 0 0 0 0
NU 0 0 0 0 0 0 0 0 0 0 0
Canada 172 2 108 62 9 653 11 507 135 49 702
PercentageTable Figure 3 - Footnote 2 95% 1% 63% 36% 5% 93% 2% 78% 21% 7% 100%

To date this season, detailed information on age and type/subtype has been received for over 643 laboratory confirmed influenza cases. Adults aged 65+ accounted 44% of reported influenza cases. Among cases of influenza A(H3N2), adults aged 65+ accounted for 47% of cases.

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, 2016-17
Age groups (years) Weekly (November 6, 2016 to November 12, 2016) Cumulative (August 28, 2016 to November 12, 2016)
Influenza A B Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) ATable 1 - Footnote UnS Total A Total A(H1) pdm09 A(H3) ATable 1 - Footnote UnS Total # %
<5 >6 0 <5 6 <5 48 0 30 18 12 60 9%
5-19 17 0 7 10 <5 60 0 48 12 <5 >60 9%
20-44 17 0 7 10 <5 >112 <5 89 23 9 >121 18%
45-64 >18 <5 13 5 <5 >126 <5 93 33 7 >133 20%
65+ 37 0 20 17 <5 >290 <5 229 61 11 >301 44%
Total 101 <5 51 48 7 643 7 489 147 >39 >643 100%
PercentageTable 1 - Footnote 2 94%       6% 94% 1% 76% 23% 6%    

Healthcare Professionals Sentinel Syndromic Surveillance

In week 45, 1.6% of visits to healthcare professionals were due to ILI. The proportion of ILI visits increased slightly from the previous week.

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17

Number of Sentinels Reporting Week 45: 95

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
Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17
Report week % Visits for ILI
35 0.99%
36 0.98%
37 0.99%
38 0.98%
39 0.96%
40 1.04%
41 2.50%
42 1.08%
43 1.02%
44 1.40%
45 1.63%
46  
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48  
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51  
52  
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Are you a primary healthcare practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel?
Please visit our Influenza Sentinel page for more details.

In week 45, two laboratory confirmed influenza outbreaks were reported: one in a long-term care (LTC) facility and one in a hospital. Additionally, one ILI outbreak was reported in a school. Of the outbreaks with known types or subtypes, the outbreak reported in a hospital was due to influenza A (unsubtyped). To date this season, 32 outbreaks have been reported and the majority (66%) have occurred in LTC facilities.

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote 1 by report week, Canada, 2016-17
Figure 5
Figure 5 - Text Description
Figure 5 - Overall number of new laboratory-confirmed influenza outbreaks by report week, Canada, 2016-17
Report week Hospitals Long Term Care Facilities Other
35 0 0 0
36 0 0 0
37 0 2 0
38 1 1 0
39 1 3 0
40 0 0 0
41 0 3 0
42 0 3 0
43 0 3 0
44 2 5 0
45 1 1 0
46 0 0 0
47 0 0 0
48 0 0 0
49 0 0 0
50 0 0 0
51 0 0 0
52 0 0 0
1 0 0 0
2 0 0 0
3 0 0 0
4 0 0 0
5 0 0 0
6 0 0 0
7 0 0 0
8 0 0 0
9 0 0 0
10 0 0 0
11 0 0 0
12 0 0 0
13 0 0 0
14 0 0 0
15 0 0 0
16 0 0 0
17 0 0 0
18 0 0 0
19 0 0 0
20 0 0 0
21 0 0 0
22 0 0 0
23 0 0 0
24 0 0 0
25 0 0 0
26 0 0 0
27 0 0 0
28 0 0 0
29 0 0 0
30 0 0 0
31 0 0 0
32 0 0 0
33 0 0 0
34 0 0 0

In week 45, a total of 16 influenza-associated hospitalizations and less than five ICU admissions were reported by participating provinces and territoriesFootnote *.  All hospitalizations in week 45 with subtype information available were due to influenza A(H3N2).

To date this season, 98 hospitalizations have been reported, of which 84% were due to influenza A(H3N2) and 64% were in adults aged 65+. Less than five ICU admissions and deaths have been reported.

Table 2 - Cumulative number of hospitalizations, ICU admissions and deaths by age and influenza type reported by participating provinces and territories, Canada 2016-17
Age Groups (years) Cumulative (August 28, 2016 to November 12, 2016)
Hospitalizations ICU Admissions Deaths
Influenza A Total Influenza B Total Total (#) Influenza A and B Total % Influenza A and B Total %
0-4 5 0 5% 0 0% 0 0%
5-19 7 <5 8% 0 0% 0 0%
20-44 10 <5 11% 0 0% 0 0%
45-64 12 <5 13% <5 50% 0 0%
65+ 64 <5 63% <5 50% <5 100%
Total 98 <5 100% <5 100% <5 100%

Pediatric Influenza Hospitalizations and Deaths

To date this season, 22 laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network. The majority of hospitalizations were due to influenza A(H3N2) (67%).

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 88 influenza viruses [75 A(H3N2), 4 A(H1N1), 9 influenza B].

Table 3 - Influenza strain characterizations, Canada, 2016-17
Strain Characterization ResultsTable 3 - Footnote 1 Count Description
Influenza A (H3N2)
Antigenically
A/Hong Kong/4801/2014-like
31 Viruses antigenically similar to A/Hong Kong/4801/2014, the A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
GeneticallyTable 3 - Footnote 2
A/Hong Kong/4801/2014-like
44 Viruses belonging to genetic group 3C.2a. A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
Influenza A (H1N1)
A/California/7/2009-like 4 Viruses antigenically similar to A/California/7/2009, the A(H1N1) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine influenza vaccine.
Influenza B
B/Brisbane/60/2008-like
(Victoria lineage)
7 Viruses antigenically similar to B/Brisbane/60/2008, the influenza B component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent influenza vaccine
B/Phuket/3073/2013-like
(Yamagata lineage)
2 Viruses antigenically similar to B/Phuket/3073/2013, the additional influenza B component of the 2016-17 Northern Hemisphere quadrivalent influenza vaccine.

During the 2016-17 season, the National Microbiology Laboratory (NML) has tested 74 influenza viruses for resistance to oseltamivir and zanamivir and 39 influenza viruses for resistance to amantadine. All 50 viruses weres sensitive to oseltamivir and zanamivir. All 39 influenza A viruses were resistant to amantadine (Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, 2016-17
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
A (H3N2) 62 0 (0%) 62 0 (0%) 36 36 (100%)
A (H1N1) 3 0 (0%) 3 0 (0%) 3 3 (100%)
B 9 0 (0%) 9 0 (0%) N/ATable 4 - Footnote * N/ATable 4 - Footnote *
TOTAL 74 0 (0%) 74 0 (0%) 39 39 (100%)

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.

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