FluWatch report: August 20 – August 26, 2017 (week 34)

Overall Summary

  • Influenza activity remains at interseasonal levels across the country, with a few regions reporting sporadic or localized activity.
  • In week 34, the majority of influenza detections were A(H3N2) with a slightly higher percentage of tests positive compared to previous seasons.
  • This is the last FluWatch report of the 2016-17 season. FluWatch will begin reporting for the 2017-2018 season on September 15, 2017 and weekly reporting will resume on week 40. 
  • For more information on the flu, see our Flu(influenza) web page.

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Influenza/Influenza-like Illness Activity (geographic spread)

In week 34, influenza or influenza-like illness activity levels remained at low levels and the majority of regions reported no activity. In week 34, one region in Ontario reported localized activity, and nine regions in British Columbia (3), Yukon, (1), Alberta (1), Ontario (2), Quebec (1), and New Brunswick (1) reported sporadic activity. For more details on a specific region, click on the map. 

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Organization:

Date published: 2017-09-01

Figure 1 – Map of overall influenza/ILI activity level by province and territory, Canada, Week 34

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 34, influenza or influenza-like illness activity levels remained at low levels and the majority of regions reported no activity. In week 34, one region in Ontario reported localized activity, and nine regions in British Columbia (3), Yukon, (1), Alberta (1), Ontario (2), Quebec (1), and New Brunswick (1) reported sporadic activity.

Laboratory Confirmed Influenza Detections

In week 34, the number of tests positive for influenza remained at interseasonal levels. The percentage of tests positive was low at 1.1%, although slightly higher than in the previous six seasons. The number of detections of influenza A has been relatively stable over the past 6 weeks; and influenza B detections have remained low. The majority of influenza A viruses subtyped were A(H3N2). 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 34

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 6 <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 45 200 0 9
48 91 272 <5 7
49 141 414 <5 12
50 297 467 <5 18
51 535 750 <5 17
52 852 1064 <5 33
1 1438 1360 <5 38
2 1510 2118 10 39
3 1350 1412 0 47
4 1334 1220 <5 47
5 1222 1290 7 62
6 1200 1225 9 81
7 1291 1141 11 97
8 1344 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
17 112 39 <5 316
18 62 49 0 283
19 36 30 0 259
20 13 26 <5 228
21 13 12 0 168
22 9 14 7 94
23 13 8 <5 75
24 0 <5 <5 48
25 7 <5 <5 29
26 9 <5 <5 21
27 9 23 <5 21
28 0 8 0 12
29 6 16 <5 <5
30 7 13 <5 <5
31 7 16 <5 6
32 0 9 <5 <5
33 16 9 0 <5
34 10 6 0 <5

To date this season, 39,355 laboratory-confirmed influenza detections have been reported, of which 88% have been influenza A. Influenza A(H3N2) has been the most common subtype detected this season, representing over 99% of 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, 2016-17, Week 34

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
Weeks (August 20, 2017 to August 26, 2017) Cumulative (August 28, 2016 to August 26, 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 3 0 0 3 1 5389 49 3338 2002 727 6116
AB 6 0 5 1 0 3877 34 3690 153 763 4640
SK 0 0 0 0 0 1798 5 1049 744 363 2161
MB 0 0 0 0 0 485 1 190 294 137 622
ON 4 0 1 3 0 9824 83 7935 1806 1211 11035
QC 1 0 0 1 0 10906 0 650 10254 985 11891
NB 0 0 0 0 0 1168 3 131 1034 162 1330
NS 0 0 0 0 0 417 0 13 404 34 451
PE 0 0 0 0 0 196 2 194 0 5 201
NL 0 0 0 0 0 448 0 43 405 62 510
YT 1 0 0 1 0 175 0 169 6 26 201
NT 0 0 0 0 0 59 0 58 1 23 82
NU 0 0 0 0 0 85 0 83 2 30 115
Canada 15 0 6 9 1 34827 177 17543 17105 4528 39355
PercentageTable Figure 3 - Footnote 2 94% 0% 40% 60% 6% 88% 1% 50% 49% 12% 100%
Table Figure 3 - Footnote 1

Specimens from NT, YT, and NU are sent to reference laboratories in other provinces.

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

Discrepancies in values in Figures 2 and 3 may be attributable to differing data sources.

Cumulative data includes updates to previous weeks.

To date this season, detailed information on age and type/subtype has been received for 27,345 laboratory-confirmed influenza cases (Table 1). Among cases with reported age and type/subtype information, adults aged 65+ accounted for nearly half of the reported influenza cases. Adults aged 65+ accounted for 51% of influenza A detections; however the majority of influenza B cases were among those less than 65 years of age.

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 34
Age groups (years) weeks 34 (August 20, 2017 to August 26, 2017) Cumulative (August 28, 2016 to August 26, 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 0 2262 23 839 1400 299 2561 9%
5-19 <5 0 <5 0 0 2223 19 1081 1123 558 2781 10%
20-44 <5 0 0 <5 0 3471 38 1816 1617 543 4014 15%
45-64 0 0 0 0 <5 3974 38 1986 1950 752 4726 17%
65+ 7 0 <5 <5 0 12177 23 5487 6667 1086 13263 49%
Total 11 0 5 6 <5 24107 141 11209 12757 3238 27345 100%
PercentageTable 1 - Footnote 2 x% x% x% x% x% 88% 1% 46% 53% 12%    
Table 1 - Footnote 1

Table 1 includes specimens for which demographic information was reported. These represent a subset of all positive influenza cases reported. Cumulative data include updates to previous weeks.

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 UnS

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

Return to first Table 1 - Footnote UnS referrer

 

x - Supressed to prevent residual disclosure

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In weeks 34, the proportion of visits to healthcare professionals due to influenza-like illness decreased from 1.8% in week 33 to 0.8% in week 34.

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, 2016-17, week 34

Number of Sentinels Reporting Week 34: 88

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 0.81%
19 0.96%
20 0.85%
21 0.94%
22 0.64%
23 0.89%
24 0.43%
25 1.48%
26 0.49%
27 1.49%
28 1.93%
29 1.12%
30 0.63%
31 1.37%
32 1.57%
33 1.79%
34 0.75%

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

During week 34, no new laboratory-confirmed influenza outbreaks were reported.

To date this season, 1,198 outbreaks have been reported and the majority (66%) have occurred in LTC facilities. Fewer outbreaks were reported this season compared to the same period in the most recent previous A(H3N2)-predominant season (2014-15) when 1,735 outbreaks were reported, of which 74% occurred in LTC facilities.

Figure 5 - Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote 1 by report week, Canada, 2016-17, week 34
Figure 5
Figure 5 - Footnote 1

All provinces and territories except NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of this report.

Return to Figure 5 - Footnote 1 referrer

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
19 2 10 3
20 0 6 3
21 0 4 1
22 2 2 0
23 1 1 2
24 0 1 0
25 0 0 0
26 0 0 0
27 0 1 1
28 0 1 0
29 0 1 0
30 0 0 0
31 0 1 0
32 0 1 0
33 1 1 0
34 0 0 0

Provincial/Territorial Influenza Hospitalizations and Deaths

During week 34, the number of influenza-associated hospitalizations reported by participating provinces and territoriesTable 1 - Footnote * remained at low levels. In week 34, five hospitalizations were reported, all were cases of influenza A in adults 65+. No intensive care unit (ICU) admissions and no deaths were reported.

To date this season, 6,546 hospitalizations have been reported, of which 88% 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 67% of the hospitalizations. A total of 274 ICU admissions and 388 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 34
Age Groups (years) Cumulative (August 28, 2016 to August 26, 2017)
Hospitalizations ICU Admissions Deaths
Influenza A Total Influenza B Total Total [# (%)] Influenza A and B Total % Influenza A and B Total %
0-4 448 95 543 (8%) 20 7% 2 1%
5-19 241 99 340 (5%) 20 7% 3 1%
20-44 298 53 351 (5%) 27 10% 5 1%
45-64 766 143 909 (14%) 83 30% 37 10%
65+ 3976 427 4403 (67%) 124 45% 341 88%
Total 5729 817 6546 (100%) 274 100% 388 100%
Table 2 - Footnote *

Note: Influenza-associated hospitalizations are not reported to PHAC by BC, NU, and QC. Only hospitalizations that require intensive medical care are reported by SK. ICU admissions are not distinguished among hospital admissions reported from ON. The hospitalization or death does not have to be attributable to influenza, a positive laboratory test is sufficient for reporting.

Return to Table 2 - Footnote * referrer

 

x - Supressed to prevent residual disclosure

Sentinel Hospital Influenza Surveillance

Pediatric Influenza Hospitalizations and Deaths

In week 34, no laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network.

To date this season, 595 laboratory-confirmed influenza-associated pediatric hospitalizations were reported by the IMPACT network. Children aged 0-23 months accounted for approximately 37% of hospitalizations and influenza A accounted for 78% of the reported hospitalizations. Among the 130 hospitalizations due to influenza B, 69 (52%) were in children 5 to 16 years of age. In comparison, children over the age of 5 years accounted for 33% of influenza A hospitalizations. Additionally, 100 intensive care unit (ICU) admissions have been reported. A total of 67 ICU cases (67%) 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 34

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 88
6-23 mo 132
2-4 yr 153
5-9 yr 119
10-16 yr 103

Figure 7 – Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, 2016-17, week 34

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 1 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 15 35 4 71
52 39 47 7 92
1 49 37 3 75
2 28 36 6 60
3 37 37 2 67
4 36 34 5 47
5 38 39 10 57
6 34 38 15 79
7 30 41 15 118
8 32 48 25 134
9 21 59 12 172
10 20 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 10 22 10 41
17 8 18 9 37
18 11 15 6 28
19 10 10 5 18
20 13 9 4 18
21 5 6 2 10
22 6 4 1 7
23 3 2 0 4
24 0 2 0 5
25 2 1 0 3
26 3 1 0 2
27 2 0 0 2
28 2 1 0 1
29 0 0 0 2
30 1 0 0 0
31 0 0 0 0
32 0 0 0 1
33 0 0 0 0
34 0 1 0 2

Adult Influenza Hospitalizations and Deaths

Surveillance for the 2016-2017 influenza season ended on April 30th, 2017 (week 20).

This season, 1,535 laboratory-confirmed influenza-associated adult (≥20 years of age) hospitalizations have been reported by the Canadian Immunization Research Network (CIRN). Influenza A accounted for 92% of hospitalizations. Adults aged 65+ accounted for 78% of hospitalizations. A total of 143 intensive care unit (ICU) admissions have been reported. Among ICU cases with available data, 126 cases (88%) reported at least one underlying condition or comorbidity. The median age of patients admitted to the ICU was 71 years. More than 86 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 20

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 237
65+ yr 1204

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 20

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= 143) Deaths (> 86)
20-44 6.1% 6.3% -
45-64 15.4% 18.9% 3.0%
65+ 78.4% 74.8% 96.6%
- Supressed due to small values

During the 2016-17 influenza season, the National Microbiology Laboratory (NML) has characterized 2,352 influenza viruses [1,658 A(H3N2), 62 A(H1N1), 632 influenza B]. Among viruses characterized during the 2016-17 season, all seasonal influenza A viruses and 20% of influenza B viruses were antigenically or genetically similar to the vaccine strains included in both the trivalent and quadrivalent vaccines. Eighty percent of influenza B viruses characterized were similar to the strain which is only included in the quadrivalent vaccine.

Table 3 – Influenza strain characterizations, Canada, 2016-17, Week 34
Strain Characterization ResultsTable 3 - Footnote 1 Count Description
Influenza A (H3N2)
Antigenically
A/Hong Kong/4801/2014-like
396 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
1261

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, one virus belonged to genetic group 3C.3a. Genetic characterization of the 396 influenza A (H3N2) viruses that underwent HI testing determined that 331 viruses belonged to genetic group 3C.2a and 65 viruses belonged to genetic group 3C.3a. The majority of viruses belonging to genetic group 3C.3a are inhibited by antisera raised against A/Hong Kong/4801/2014Table 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 62 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)
128 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)
504 Viruses antigenically similar to B/Phuket/3073/2013, the additional influenza B component of the 2016-17 Northern Hemisphere quadrivalent influenza vaccine.
Table 3 - Footnote 1

The NML receives a proportion of the influenza positive specimens from provincial laboratories for strain characterization and antiviral resistance testing. Strain characterization data reflect the results of hemagglutination inhibition (HI) testing compared to the reference influenza strains recommended by WHO.

Return to Table 3 - Footnote 1 referrer

Table 3 - Footnote 2

Determined by sequence analysis

Return to Table 3 - Footnote 2 referrer

Table 3 - Footnote 3

WHO - Recommended composition of the influenza virus vaccines for use in the 2016-17 northern hemisphere influenza season.

Return to Table 3 - Footnote 3 referrer

Table 3 - Footnote 4

Detected in epidemiological week 50. For more details, see Week 50 report

Return to Table 3 - Footnote 4 referrer

During the 2016-17 season, the National Microbiology Laboratory (NML) has tested 1,260 influenza viruses for resistance to oseltamivir, 1,260 influenza viruses for resistance to zanamivir and 288 influenza viruses for resistance to amantadine. All but two influenza A(H3N2) viruses and one of the A(H1N1) viruses were sensitive to oseltamivir and all viruses were sensitive to zanamivir. All 288 influenza A viruses were resistant to amantadine (Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, 2016-17, Week 34
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
A (H3N2) 765 2 (0.3%) 764 0 (0%) 232 232 (100%)
A (H3N2v) 1 0 (0%) 1 0 (0%) 1 1 (100%)
A (H1N1) 52 1 (1.9%) 51 0 (0%) 55 55 (100%)
B 442 0 (0%) 444 0 (0%) N/ATable 4 - Footnote * N/ATable 4 - Footnote *
TOTAL 1260 3 (0.2%) 1260 0 (0%) 288 288 (100%)
Table 4 - Footnote *

N/A - not applicable

Return to first Table 4 - Footnote * referrer

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.

Footnote *

More than just sporadic as determined by the provincial/territorial epidemiologist.

Return to footnote * referrer

Footnote †

Influenza surveillance regions within the province or territory as defined by the provincial/territorial epidemiologist.

Return to footnote referrer


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