FluWatch report: October 23 to October 29, 2016 (week 43)

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Organization: Public Health Agency of Canada

Date published: 2016-11-04

  • Influenza activity is at interseasonal levels with the majority regions in Canada reporting low or no influenza activity.
  • A total of 85 positive influenza detections were reported in week 43. Influenza A(H3N2) continues to be the most common subtype detected.
  • In week 43, 1.0% of visits to sentinel healthcare professionals were due to influenza-like symptoms.
  • One laboratory-confirmed influenza outbreak was reported in week 43.
  • Five hospitalizations were reported in week 43; all  in adults ≥65 years and all due to influenza A(H3N2).
  • For more information on the flu, see our Flu(influenza) web page.

In week 43, a total of 29 regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 23 regions across ten provinces. Localized activity was reported in one region in 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 43
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 43, a total of 29 regions in Canada reported no influenza activity. Sporadic influenza activity was reported in 23 regions across ten provinces. Localized activity was reported in one region in ON

The percentage of tests positive for influenza increased in week 43 but remained at interseasonal levels, with 2.9% of tests positive. 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 30 49 <5 6
43 39 61 <5 <5
44 0 0 0 0
45 0 0 0 0
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 43, there were 85 positive influenza tests. Influenza A(H3N2) was the most common subtype detected. BC accounted for the majority (53%) of influenza detections in week 43. To date, influenza A(H3N2) is the most common subtype detected, representing 74% of laboratory-confirmed cases. 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 23, 2016 to October 29, 2016) Cumulative (August 28, 2016 to October 29, 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 >37 <5 25 12 <5 >158 <5 142 16 6 >164
AB >8 <5 8 0 <5 >79 <5 68 11 10 >89
SK 0 0 0 0 0 0 0 0 0 0 0
MB <5 0 <5 0 0 7 0 <5 <5 <5 <7
ON >19 <5 12 7 <5 >69 <5 48 21 11 >80
QC 5 0 0 5 <5 >30 0 <5 30 5 >35
NB 0 0 0 0 0 <5 0 <5 <5 0 <5
NS <5 0 <5 0 0 <5 0 <5 0 0 <5
PE 0 0 0 0 0 0 0 0 0 0 0
NL 0 0 0 0 0 <5 0 <5 0 0 <5
YT 5 0 <5 <5 0 21 0 12 9 0 21
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 >74 <5 >45 >24 5 >364 9 >270 >87 >32 >396
PercentageTable Figure 3 - Footnote 2 94% 4% 61% 35% 6% 92% 2% 74% 24% 10% 100%

To date this season, detailed information on age and type/subtype has been received for over 412 laboratory confirmed influenza cases. Adults aged 65+ accounted 46% of reported influenza cases. Among cases of influenza A(H3N2), adults aged 65+ accounted for 50% 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 (October 23, 2016 to October 29, 2016) Cumulative (August 28, 2016 to October 29, 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 <5 0 <5 <5 <5 30 0 18 12 7 9%
5-19 10 0 5 5 0 27 0 20 7 <5 7%
20-44 >5 0 <5 5 0 >58 <5 43 15 8 16%
45-64 >8 0 <5 8 0 >81 <5 52 29 6 21%
65+ 20 0 8 12 0 >182 <5 134 48 8 46%
Total >48 0 20 32 <5 383 5 267 111 >29 100%
PercentageTable 1 - Footnote 2 98% 0% 38% 62% 2% 93% 1% 70% 29% 7%  

Healthcare Professionals Sentinel Syndromic Surveillance

In week 43, 1.0% of visits to healthcare professionals were due to ILI. The proportion of ILI visits remained constant since the previous week.

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

Number of Sentinels Reporting Week 43: 83

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 1.03
44  
45  
46  
47  
48  
49  
50  
51  
52  
1  
2  
3  
4  
5  
6  
7  
8  
9  
10  
11  
12  
13  
14  
15  
16  
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18  
19  
20  
21  
22  
23  
24  
25  
26  
27  
28  
29  
30  
31  
32  
33  
34  

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 43, one laboratory confirmed influenza outbreak was reported. The outbreak was in a long-term care facility and due to influenza A (unsubtyped). To date this season, 18 outbreaks have been reported.

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 2 0
43 0 1 0
44 0 0 0
45 0 0 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 43, a total of five influenza-associated hospitalizations and less than five ICU admissions were reported by participating provinces and territoriesFootnote *.  All hospitalizations and ICU admissions in week 43 were due to influenza A(H3N2).

To date this season, more than 45 hospitalizations have been reported, of which 33 (73%) were due to influenza A(H3N2) and 64% were in adults 65+. Less than five ICU admissions and no 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 October 29, 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 <5 <5 <5 0 0% 0 0%
20-44 <5 <5 <5 0 0% 0 0%
45-64 <5 <5 <5 0 0% 0 0%
65+ 30 <5 >30 <5 100% 0 0%
Total 45 <5 45 <5 100% 0 0%

Pediatric Influenza Hospitalizations and Deaths

To date this season, less than five laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network.

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 49 influenza viruses [38 A(H3N2), 2 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
17 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
21 Viruses belonging to a genetic group for which most viruses were antigenically related to A/Hong Kong/4801/2014, the A(H3N2) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent vaccine.
Influenza A (H1N1)
A/California/7/2009-like 2 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 50 influenza viruses for resistance to oseltamivir and zanamivir and 30 influenza viruses for resistance to amantadine. All 50 viruses weres sensitive to oseltamivir and zanamivir. All 30 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) 41 0 (0%) 41 0 (0%) 28 28 (100%)
A (H1N1) 2 0 (0%) 2 0 (0%) 2 2 (100%)
B 7 0 (0%) 7 0 (0%) N/ATable 4 - Footnote * N/ATable 4 - Footnote *
TOTAL 50 0 (0%) 50 0 (0%) 30 30 (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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