FluWatch report: April 30 to May 6, 2017 (week 18)

Overall Summary

  • Overall, influenza activity continues to decline slowly in Canada.
  • The provinces of Ontario and Quebec accounted for the majority (60%) of all influenza laboratory detections for week 18.
  • In week 18, influenza B accounted for the majority of influenza activity in Canada, with 70% or more of influenza laboratory detections, and outbreaks due to influenza B.
  • This increase in influenza B activity is expected as influenza B often appears later in the flu season.
  • The majority of laboratory detections, hospitalizations and deaths have been among adults aged 65+ years.
  • For more information on the flu, see our Flu(influenza) web page.

On this page

Influenza/Influenza-like Illness Activity (geographic spread)

In week 18, 15 regions across eight provinces and territories reported no influenza or influenza-like illness activity. Sporadic influenza activity was reported in 28 regions across ten provinces and territories. Localized activity was reported in ten regions across three provinces. For more details on a specific region, click on the map.

Download the alternative format
(PDF format, 880 KB, 9 pages)

Organization:

Date published: 2017-05-12

Figure 1 – Map of overall influenza/ILI activity level by province and territory, Canada, week 18

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 18, 15 regions across eight provinces and territories reported no influenza or influenza-like illness activity. Sporadic influenza activity was reported in 26 regions across nine provinces and territories. Localized activity was reported in nine regions across two provinces.

Laboratory Confirmed Influenza Detections

In week 18, the number (370) and the percentage (9.5%) of tests positive for influenza decreased from the previous week. Influenza B was the most common type of influenza detected in all jurisdictions in Canada. Since week 16, the percentage of tests positive for influenza B has plateaued (6.6% to 6.9%), but has not yet begun a clear decline. Overall in week 18, influenza B, accounted for 70% of total detections. The number of influenza B detections remains low compared to the same time period in recent seasons. 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, week 18

Figure 2

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.

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 19 110 <5 9
45 31 150 <5 11
46 52 140 <5 7
47 54 200 0 9
48 91 272 <5 7
49 148 414 <5 12
50 305 467 <5 18
51 535 750 <5 17
52 857 1064 <5 33
1 1444 1360 <5 38
2 1516 2118 10 39
3 1354 1412 0 47
4 1336 1220 <5 47
5 1222 1290 7 62
6 1200 1225 9 81
7 1291 1141 11 97
8 1345 899 17 128
9 977 935 7 159
10 802 726 14 203
11 629 347 13 242
12 498 259 <5 302
13 369 221 0 309
14 273 134 6 365
15 216 73 0 321
16 167 59 9 347
17 118 36 <5 316
18 67 43 <5 281
19 #N/A #N/A #N/A #N/A
20 #N/A #N/A #N/A #N/A
21 #N/A #N/A #N/A #N/A
22 #N/A #N/A #N/A #N/A
23 #N/A #N/A #N/A #N/A
24 #N/A #N/A #N/A #N/A
25 #N/A #N/A #N/A #N/A
26 #N/A #N/A #N/A #N/A
27 #N/A #N/A #N/A #N/A
28 #N/A #N/A #N/A #N/A
29 #N/A #N/A #N/A #N/A
30 #N/A #N/A #N/A #N/A
31 #N/A #N/A #N/A #N/A
32 #N/A #N/A #N/A #N/A
33 #N/A #N/A #N/A #N/A
34 #N/A #N/A #N/A #N/A

To date this season, 38,024 laboratory confirmed influenza detections have been reported, of which 91% have been influenza A. Influenza A(H3N2) has been the most common subtype detected this season. 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, week 18

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 (April 30, 2017 to May 6, 2017) Cumulative (August 28, 2016 to May 6, 2017)
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 5 1 3 1 17 5324 43 3297 1984 656 5980
AB 5 0 1 4 53 3796 24 3629 143 561 4357
SK 1 0 1 0 23 1760 4 1024 732 252 2012
MB 7 0 3 4 8 483 0 182 301 110 593
ON 40 2 33 5 79 9725 73 7871 1781 962 10687
QC 43 0 0 43 64 10831 2 650 10179 788 11619
NB 4 0 0 4 12 1151 3 126 1022 116 1267
NS 2 0 0 2 4 414 0 13 401 29 443
PE 0 0 0 0 0 196 2 194 0 4 200
NL 3 0 0 3 5 444 0 43 401 25 469
YT 0 0 0 0 2 213 0 164 49 18 231
NT 0 0 0 0 1 59 0 58 1 17 76
NU 0 0 0 0 0 85 0 83 2 5 90
Canada 110 3 41 66 268 34481 151 17334 16996 3543 38024
PercentageTable Figure 3 - Footnote 2 29% 3% 37% 60% 71% 91% 0% 50% 49% 9% 100%

To date this season, detailed information on age and type/subtype has been received for 26,290 laboratory-confirmed influenza cases (Table 1). Among cases with reported age and type/subtype information, adults aged 65+ accounted for half of the reported influenza cases. Adults aged 65+ have predominantly been affected by influenza A accounting for 51% of influenza A detections. Influenza B, while much smaller in number, is mainly affecting individuals less than 65 years of age. Individuals less than 65 years of age accounted for 67% of influenza B detections.

Table 1 - Weekly and cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reportingTable 1 - Footnote 1, Canada, 2016-17, Week 18
Age groups (years) Weekly (April 30, 2017 to May 6, 2017) Cumulative (August 28, 2016 to May 6, 2017)
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 # %
0-4 <5 0 0 <5 9 2233 13 826 1394 216 2449 9%
5-19 >5 0 <5 5 29 2207 11 1076 1120 423 2630 10%
20-44 >8 0 <5 8 28 3418 23 1799 1596 432 3850 15%
45-64 >16 0 <5 16 33 3900 21 1946 1933 585 4485 17%
65+ 19 0 0 19 61 12060 10 5424 6626 816 12876 49%
Total 58 0 6 >48 160 23818 78 11071 12669 2472 26290 100%
PercentageTable 1 - Footnote 2 27% 0% x% x% 73% 91% 0% 46% 53% 9%    

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 18, 0.8% of visits to healthcare professionals were due to influenza-like illness, a decrease compared to the percentage of visits reported in week 17.

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17, week 18

Number of Sentinels Reporting Week 18: 107

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 0.96%
36 0.96%
37 0.98%
38 0.96%
39 0.94%
40 1.03%
41 2.41%
42 1.04%
43 1.01%
44 1.39%
45 1.32%
46 0.97%
47 1.11%
48 1.07%
49 1.08%
50 1.30%
51 1.73%
52 2.83%
1 1.96%
2 2.22%
3 1.92%
4 2.02%
5 2.31%
6 3.13%
7 1.73%
8 2.19%
9 1.82%
10 1.77%
11 1.70%
12 1.13%
13 1.18%
14 1.31%
15 0.88%
16 0.98%
17 0.86%
18 0.78%

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.

Influenza Outbreak Surveillance

In week 18, 13 laboratory-confirmed influenza outbreaks were reported, a decrease from the previous week. Of the seven outbreaks with known strains or subtypes: two were due to influenza A and six were due to influenza B.

To date this season, 1,149 outbreaks have been reported and the majority (66%) have occurred in LTC facilities. A total of 71 outbreaks (6%) due to influenza B have been reported.

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote 1 by report week, Canada, 2016-17, week 18
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 1
39 1 3 1
40 0 0 0
41 0 3 0
42 0 3 1
43 0 3 0
44 2 5 2
45 1 1 0
46 2 6 0
47 1 8 0
48 0 2 0
49 1 14 3
50 4 15 4
51 5 32 13
52 7 65 18
1 15 84 22
2 13 83 24
3 19 44 9
4 8 39 8
5 13 36 11
6 4 46 20
7 8 38 8
8 5 39 17
9 4 32 9
10 3 32 9
11 7 22 12
12 2 28 6
13 1 24 8
14 0 11 7
15 1 14 6
16 2 8 1
17 0 12 6
18 1 6 6

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 18, 75 influenza-associated hospitalizations were reported by participating provinces and territories*, a slight decrease from 78 reported in the previous week. In week 18, 52% of hospitalizations occurred in adults 65+ and influenza B accounted for 61% of reported hospitalizations. Additionally,eight intensive care unit (ICU) admissions and six deaths were reported.

To date this season, 6,220 hospitalizations have been reported, of which 91% were due to influenza A. Among cases for which the subtype of influenza A was reported, 99% were influenza A(H3N2). Adults 65+ accounted for 68% of the hospitalizations. A total of 251 ICU admissions and 361 deaths have been reported. The majority of deaths (88%) were reported in adults aged 65+ years.

Table 2 - Cumulative number of hospitalizations, ICU admissions and deaths by age and influenza type reported by participating provinces and territories, Canada 2016-17, week 18
Age Groups (years) Cumulative (August 28, 2016 to May 6, 2017)
Hospitalizations ICU Admissions Deaths
Influenza A Total Influenza B Total Total [# (%)] Influenza A and B Total % Influenza A and B Total %
0-4 442 61 503 (8%) 17  7% <5 Table 2 - Footnote x%
5-19 238 72 310 (5%) 18  7% <5 Table 2 - Footnote x%
20-44 292 35 327 (5%) 23  9% 5  1%
45-64 758 106 864 (14%) 75  30% 35  10%
65+ 3900 316 4216 (68%) 118  47% 316  88%
Total 5630 590 6220 (100%) 251  100% 361  100%

Sentinel Hospital Influenza Surveillance

Pediatric Influenza Hospitalizations and Deaths

In week 18, ten laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network, of which nine were associated with influenza B. Pediatric hospitalizations have been declining since the peak in early January. The number of weekly hospitalizations has been below the six year average since early February (Figure 7).

To date this season, 541 laboratory-confirmed influenza-associated pediatric hospitalizations were reported by the IMPACT network. Children aged 0-23 months accounted for approximately 38% of hospitalizations and influenza A accounted for 83% of the reported hospitalizations. Among the 93 hospitalizations due to influenza B, 50 (54%) were in children over the age of 5 years. In comparison, children over the age of 5 years accounted for 33% of influenza A hospitalizations. Additionally, 92 intensive care unit (ICU) admissions have been reported. A total of 63 ICU cases (68%) reported at least one underlying condition or comorbidity. Less than five deaths have been reported this season.

Figure 6 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, 2016-17, week 18

Figure 6
Figure 6 - Text Description
Figure 6 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, 2016-17
Age Group Total
0-5 mo 82
6-23 mo 121
2-4 yr 140
5-9 yr 104
10-16 yr 94

Figure 7 – Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, 2016-17, week 18

Figure 7

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2015-16.

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

Figure 7 - Text Description
Figure 7 - Number of pediatric (≤16 years of age) hospitalizations reported by IMPACT sentinel hospital network, by week, Canada, 2016-17
Report week 2016-17 Average Min Max
35 0 0 0 0
36 0 0 0 0
37 0 1 0 2
38 0 1 0 2
39 3 0 0 1
40 2 0 0 1
41 0 1 0 2
42 4 1 0 1
43 3 1 0 3
44 6 2 1 4
45 3 3 2 4
46 5 5 1 13
47 3 5 0 9
48 7 10 1 22
49 10 15 2 28
50 19 24 4 47
51 17 35 4 71
52 38 47 7 92
1 48 37 3 75
2 26 36 6 60
3 38 37 2 67
4 35 34 5 47
5 38 39 10 57
6 33 38 15 79
7 29 41 15 118
8 33 48 25 134
9 20 59 12 172
10 17 48 17 114
11 19 45 17 118
12 13 39 14 96
13 14 33 14 57
14 14 27 12 56
15 15 25 14 56
16 11 22 10 41
17 7 18 9 37
18 10 15 6 28
19 #N/A 10 5 18
20 #N/A 9 4 18
21 #N/A 6 2 10
22 #N/A 4 1 7
23 #N/A 2 0 4
24 #N/A 2 0 5
25 #N/A 1 0 3
26 #N/A 1 0 2
27 #N/A 0 0 2
28 #N/A 1 0 1
29 #N/A 0 0 2
30 #N/A 0 0 0
31 #N/A 0 0 0
32 #N/A 0 0 1
33 #N/A 0 0 0
34 #N/A 1 0 2

Adult Influenza Hospitalizations and Deaths

In week 18, two laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations were reported by the Canadian Immunization Research Network (CIRN), a decrease from the previous week. In week 18 influenza B accounted for all reported hospitalizations.

To date this season, 1,535 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by CIRN. Influenza A accounted for 93% of hospitalizations. Adults aged 65+ accounted for 78% of hospitalizations. To date, 141 intensive care unit (ICU) admissions have been reported. Among cases with available data, 120 ICU cases (85%) reported at least one underlying condition or comorbidity. The median age of patients admitted to the ICU was 71 years. Approximately 84 deaths have been reported this season, the majority in adults aged 65+. The median age of reported deaths was 85 years.

Figure 8 - Cumulative numbers of adult hospitalizations (≥20 years of age) with influenza by type and age-group reported by CIRN, Canada, 2016-17, week 18

Figure 8
Figure 8 - Text Description
Figure 8 - Cumulative numbers of adult hospitalizations (≥20 years of age) with influenza by type and age-group reported by the CIRN network, Canada, 2016-17
Age Group Total
20-44 yr 94
45-64 yr 236
65+ yr 1205

Figure 9 – Percentage of hospitalizations, ICU admissions and deaths with influenza by age-group (≥20 years of age) reported by CIRN, Canada 2016-17, week 18

Figure 9

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

Figure 9 - Text Description
Figure 9 - Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group (≥20 year of age), CIRN, Canada, 2016-17
Age-group (years) Hospitalizations (n= 1535) ICU admissions (n= 141) Deaths (n= 84)
- Supressed due to small values
20-44 6.1% 5.7% -
45-64 15.4% 19.1% 5.0%
65+ 78.5% 75.2% 96.6%

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 1,844 influenza viruses [1527 A(H3N2), 36 A(H1N1), 281 influenza B]. All but one influenza A virus (n=1526) and 61 influenza B viruses characterized were antigenically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Two hundred and twenty influenza B viruses were similar to the strain which is only included in the quadrivalent vaccine.

Table 3 – Influenza strain characterizations, Canada, 2016-17, Week 18
Strain Characterization ResultsTable 3 - Footnote 1 Count Description
Influenza A (H3N2)
Antigenically
A/Hong Kong/4801/2014-like
357 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
1169

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.

Additionally, genetic characterization of the 357 influenza A (H3N2) viruses that underwent HI testing determined that 294 viruses belonged to genetic group 3C.2a and 63 viruses belonged to genetic group 3C.3a. Sequencing is pending for the remaining XX isolates. The majority of viruses belonging to genetic group 3C.3a are inhibited by antisera raised against A/Hong Kong/4801/20143Table 3 - Footnote 3.

Antigenically
A/Indiana/10/2011-likeTable 3 - Footnote 4
1

Viruses antigenically similar to A/Indiana/10/2011, a candidate H3N2v vaccine virus.

Influenza A (H1N1)
A/California/7/2009-like 36 Viruses antigenically similar to A/California/7/2009, the A(H1N1) component of the 2016-17 Northern Hemisphere's trivalent and quadrivalent influenza vaccine.
Influenza B
B/Brisbane/60/2008-like
(Victoria lineage)
61 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)
220 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 1029 influenza viruses for resistance to oseltamivir, 1028 influenza viruses for resistance to zanamivir and 226 influenza viruses for resistance to amantadine. All but two influenza A(H3N2) viruses were sensitive to oseltamivir and all viruses were sensitive to zanamivir. All 226 influenza A viruses were resistant to amantadine (Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, 2016-17, Week 18
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
A (H3N2) 739 2 (0.3%) 738 0 (0%) 196 196 (100%)
A (H3N2v) 1 0 (0%) 1 0 (0%) 1 1 (100%)
A (H1N1) 35 0 (0%) 34 0 (0%) 29 29 (100%)
B 254 0 (0%) 255 0 (0%) N/ATable 4 - Footnote * N/ATable 4 - Footnote *
TOTAL 1029 2 (0.2%) 1028 0 (0%) 226 226 (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.


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

Privacy statement

Thank you for your help!

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

Date modified: