FluWatch report: August 27 – September 9, 2017 (weeks 35 & 36)

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 36, one region in Alberta reported localized activity, and 11 regions in British Columbia (3), Alberta (3), Ontario (4), and Quebec (1) reported sporadic activity.

Laboratory Confirmed Influenza Detections

In weeks 35-36, the number of tests positive for influenza remained at interseasonal levels. The percentage of tests positive was low but increased slightly from 1.9 to 2.4% in weeks 35 and 36, which is higher for this time of year than was observed during the previous seven seasons. The number of detections of influenza A has increased during this two-week period, while influenza B detections have remained low. The majority of influenza A viruses subtyped were A(H3N2). For data on other respiratory virus detections, see Respiratory Virus Detections in Canada Report.

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	4	20	6	5
36	7	28	1	2
37	0	0	0	0
38	0	0	0	0
39	0	0	0	0
40	0	0	0	0
41	0	0	0	0
42	0	0	0	0
43	0	0	0	0
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

To date this season, 73 laboratory-confirmed influenza detections have been reported, of which 90% have been influenza A. Influenza A(H3N2) has been the most common subtype detected this season, representing 87% of influenza A detections. Detections from BC and AB represent 74% of the cases reported in this 2-week period. 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 - 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	Week (September 3, 2017 to September 9)					Cumulative (August 27, 2017 to September 9, 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	24	1	20	3	1	25	1	20	4	1	26
AB	24	6	18	0	4	24	6	18	0	4	28
SK	0	0	0	0	0	0	0	0	0	0	0
MB	0	0	0	0	0	0	0	0	0	0	0
ON	12	0	8	4	1	12	0	8	4	1	13
QC	1	0	0	1	0	1	0	0	1	0	1
NB	1	0	0	1	0	1	0	0	1	0	1
NS	0	0	0	0	0	0	0	0	0	0	0
PE	0	0	0	0	0	0	0	0	0	0	0
NL	0	0	0	0	0	0	0	0	0	0	0
YT	3	0	2	1	0	3	0	2	1	0	3
NT	0	0	0	0	0	0	0	0	0	0	0
NU	0	0	0	0	1	0	0	0	0	1	1
Canada	65	7	48	10	7	66	7	48	11	7	73
PercentageTable Figure 3 - Footnote 2	90%	11%	74%	15%	10%	90%	11%	73%	17%	10%	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 more than 45 laboratory-confirmed influenza cases (Table 1). Based on the limited data to date, among influenza cases with reported age and type/subtype information, more than half of cases were in adults aged 65 years and older.

Table 1 - Cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reporting, Canada, 2017-18, weeks 35 to 36

Age groups (years)	Cumulative (August 27, 2017 to September 9, 2017)
	Influenza A				B	Influenza A and B
	A Total	A(H1) pdm09	A(H3)	A (UnS)Footnote 1	Total	#	%
0-4	<5	<5	0	0	<5	5	11%
5-19	<5	<5	<5	0	<5	5	11%
20-44	8	0	8	0	0	8	17%
45-64	<5	0	<5	0	0	<5	4%
65+	27	<5	23	<5	0	27	57%
Total	>40	6	34	<5	<5	>45	100%
Tableau 1 - Note 1 UnS: unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available; Return to Table 1 - Note 1 Tableau 1 - Note x Supressed to prevent residual disclosure Return to Table 1 - Note x

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 36, 0.8% of visits to healthcare professionals were due to influenza-like illness.

The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2012-13 to 2016-17

Figure 4 - Text Description

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

Report week	2017-18	Average	Min	Max
35	0.7%	0.8%	0.5%	1.2%
36	0.8%	0.8%	0.7%	1.0%
37	0.0%	0.9%	0.7%	1.0%
38	0.0%	1.1%	1.0%	1.4%
39	0.0%	1.1%	0.9%	1.4%
40	0.0%	1.3%	0.9%	1.6%
41	0.0%	1.4%	0.9%	2.4%
42	0.0%	1.4%	1.0%	1.9%
43	0.0%	1.3%	1.0%	1.5%
44	0.0%	1.3%	0.9%	1.6%
45	0.0%	1.3%	1.2%	1.5%
46	0.0%	1.6%	1.0%	2.0%
47	0.0%	1.5%	1.1%	1.9%
48	0.0%	1.6%	0.8%	2.1%
49	0.0%	1.5%	1.0%	2.5%
50	0.0%	2.3%	1.3%	3.7%
51	0.0%	2.5%	1.6%	4.1%
52	0.0%	4.5%	1.7%	7.1%
1	0.0%	3.7%	1.7%	5.2%
2	0.0%	3.0%	1.1%	4.5%
3	0.0%	2.5%	1.3%	3.6%
4	0.0%	2.4%	1.7%	3.5%
5	0.0%	2.7%	2.0%	4.4%
6	0.0%	2.7%	2.1%	3.3%
7	0.0%	2.4%	1.7%	3.0%
8	0.0%	2.3%	1.9%	2.7%
9	0.0%	2.2%	1.8%	2.7%
10	0.0%	2.1%	1.8%	2.7%
11	0.0%	2.1%	1.7%	2.7%
12	0.0%	1.8%	1.1%	2.7%
13	0.0%	1.7%	1.2%	2.6%
14	0.0%	1.8%	1.3%	2.4%
15	0.0%	1.6%	0.9%	1.9%
16	0.0%	1.5%	1.0%	1.9%
17	0.0%	1.5%	0.9%	2.2%
18	0.0%	1.2%	0.8%	1.6%
19	0.0%	1.3%	1.0%	1.7%
20	0.0%	1.2%	0.9%	1.4%
21	0.0%	0.9%	0.3%	1.3%
22	0.0%	0.8%	0.6%	1.0%
23	0.0%	0.9%	0.6%	1.2%
24	0.0%	0.7%	0.4%	1.0%
25	0.0%	1.2%	0.5%	1.6%
26	0.0%	0.8%	0.4%	1.4%
27	0.0%	0.8%	0.4%	1.5%
28	0.0%	1.0%	0.6%	1.9%
29	0.0%	0.8%	0.5%	1.1%
30	0.0%	0.5%	0.3%	0.7%
31	0.0%	0.9%	0.3%	1.4%
32	0.0%	1.0%	0.6%	1.6%
33	0.0%	1.2%	0.4%	2.1%
34	0.0%	0.7%	0.5%	0.9%

Participatory Syndromic Surveillance

FluWatchers is a participatory ILI surveillance system that relies on weekly voluntary submissions of syndromic information from the Canadians across Canada.

The 2017-18 FluWatchers reporting season will begin October 1st, 2017 (week 40).

Influenza Outbreak Surveillance

In weeks 35-36, one new laboratory-confirmed influenza outbreak was reported in a long-term care facility.

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

Report week	Hospitals	Long Term Care Facilities	Other
35	0	0	0
36	0	1	0
37	0	0	0
38	0	0	0
39	0	0	0
40	0	0	0
41	0	0	0
42	0	0	0
43	0	0	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

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In weeks 35-36, the number of weekly influenza-associated hospitalizations reported by participating provinces and territories^{Footnote 1} remained at low levels with fewer than five hospitalizations reported during this 2-week period.

Pediatric Influenza Hospitalizations and Deaths

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

Influenza Strain Characterizations

The National Microbiology Laboratory has not yet reported influenza strain characterization results for influenza viruses collected during the 2017-18 season.

Antiviral Resistance

The National Microbiology Laboratory has not yet reported antiviral resistance results for influenza viruses collected during the 2017-18 season.

Provincial and International Influenza Reports

FluWatch definitions for the 2017-2018 season

The FluWatch report is compiled from a number of data sources. Surveillance information contained in this report is a reflection of the surveillance data available to FluWatch at the time of production. Delays in reporting of data may cause data to change retrospectively

Influenza/Influenza-like Illness (ILI) Activity
Influenza/ILI activity levels, as represented on the map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, primary care consultations for ILI and reported outbreaks. ILI data may be reported through sentinel physicians, emergency room visits or health line telephone calls, and the detemination of an increase is based on the assessment of the provincial/territorial epidemiologist. Maps from previous weeks, including any retrospective updates, are available in the mapping feature found in the Weekly Influenza Reports.

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 ILI^{Footnote *} 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 region^{Footnote †}

4 = Widespread:

1. evidence of increased ILI^{Footnote *} 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 region^{Footnote †}

Laboratory-Confirmed Influenza Detections
Provincial, regional and some hospital laboratories report the weekly number of tests and detections of influenza and other respiratory viruses. Provincial public health laboratories submit demographic information for cases of influenza. This case-level data represents a subset of influenza detections reported through aggregate reporting. Specimens from NT, YT, and NU are sent to reference laboratories in the provinces for testing.

Syndromic/Influenza-like Illness Surveillance
FluWatch maintains a network of primary care practitioners who report the weekly proportion of ILI cases seen in their practice. Independent sentinel networks in BC, AB, and SK compile their data for reporting to FluWatch. Not all sentinel physicians report every week.

Definition of 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 years of age, gastrointestinal symptoms may also be present. In patients under 5 or 65 years and older, fever may not be prominent.

Influenza Outbreak Surveillance
Outbreaks of influenza or ILI are reported from all provinces and territories, according to the definitions below. However, reporting of outbreaks of influenza/ILI from different types of facilities differs between jurisdictions. All provinces and territories with the exception of NU report influenza outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals.

Outbreak definitions:
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.
Hospitals and residential institutions: two or more cases of ILI within a seven-day period, including at least one laboratory-confirmed case of influenza. Residential institutions include but are 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 of influenza; i.e. closed communities.

Serious Outcome Influenza Surveillance
Provincial/Territorial Influenza Hospitalizations and Deaths
Influenza-associated hospitalizations and deaths are reported by 8 Provincial and Territorial Ministries of Health (excluding BC, NU, ON and QC). The hospitalization or death does not have to be attributable to influenza, a positive laboratory test is sufficient for reporting. Only hospitalizations that require intensive medical care are reported by SK.
Due to changes in participating provinces and territories, comparisons to previous years should be done with caution.
Pediatric Influenza Hospitalizations and Deaths
The Immunization Monitoring Program Active (IMPACT) network reports the weekly number of hospitalizations with influenza among children admitted to one of the 12 participating paediatric hospitals in 8 provinces. These represent a subset of all influenza-associated pediatric hospitalizations in Canada.

Influenza Strain Characterizations and Antiviral Resistance
Provincial public health laboratories send a subset of influenza virus isolates to the National Microbiology Laboratory for strain characterization and antiviral resistance. These represent a subset of all influenza detections in Canada and the proportion of isolates of each type and subtype is not necessarily representative of circulating viruses.
Antigenic strain characterization data reflect the results of hemagglutination inhibition (HI) testing compared to the reference influenza strains recommended by WHO. Genetic strain characterization data are based on analysis of the sequence of the viral hemagglutinin (HA) gene.

Antiviral resistance testing is conducted by phenotypic and genotypic methods on influenza virus isolates submitted to the National Microbiology Laboratory. All isolates are tested for oseltamivir and zanamivir and a subset are tested for resistance to amantadine.

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).

This report is available on the Government of Canada Influenza webpage.
Ce rapport est disponible dans les deux langues officielles.

We would like to thank all the Fluwatch surveillance partners who are participating in this year's influenza surveillance program.