FluWatch report: February 11 to February 17, 2018 (week 7)

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

Figure 1 - Map of overall influenza/ILI activity level by province and territory, Canada, week 2018-07

Influenza Surveillance Region	Activity Level
Newfoundland - Central	Localized
Newfoundland - Eastern	Localized
Grenfell Labrador	Sporadic
Newfoundland - Western	Localized
Prince Edward Island	Localized
Nova Scotia - Central (Zone 4)	Localized
Nova Scotia - Western (Zone 1)	Sporadic
Nova Scotia - Northern (Zone 2)	No Activity
Nova Scotia - Eastern (Zone 3)	Localized
New Brunswick - Public Health Region 1	Sporadic
New Brunswick - Public Health Region 2	Localized
New Brunswick - Public Health Region 3	Localized
New Brunswick - Public Health Region 4	Sporadic
New Brunswick - Public Health Region 5	Sporadic
New Brunswick - Public Health Region 6	Sporadic
New Brunswick - Public Health Region 7	Sporadic
Nord-est Québec	Localized
Québec et Chaudieres-Appalaches	Sporadic
Centre-du-Québec	Widespread
Montréal et Laval	Widespread
Ouest-du-Québec	Widespread
Montérégie	Widespread
Ontario - Central East	Widespread
Ontario - Central West	Localized
Ontario - Eastern	Localized
Ontario - North East	Localized
Ontario - North West	Localized
Ontario - South West	Localized
Ontario - Toronto	Localized
Manitoba - Interlake-Eastern	Sporadic
Manitoba - Northern Regional	Sporadic
Manitoba - Prairie Mountain	Sporadic
Manitoba - South	Sporadic
Manitoba - Winnipeg	Sporadic
Saskatchewan - North	Sporadic
Saskatchewan - Central	Sporadic
Saskatchewan - South	Sporadic
Alberta - North Zone	Sporadic
Alberta - Edmonton	Localized
Alberta - Central Zone	Sporadic
Alberta - Calgary	Localized
Alberta - South Zone	Sporadic
British Columbia - Interior	Localized
British Columbia - Fraser	Sporadic
British Columbia - Vancouver Coastal	Sporadic
British Columbia - Vancouver Island	Localized
British Columbia - Northern	Sporadic
Yukon	Sporadic
Northwest Territories - North	Sporadic
Northwest Territories - South	Sporadic
Nunavut - Baffin	Localized
Nunavut - Kivalliq	Localized
Nunavut - Kitimeot	Sporadic

Laboratory-Confirmed Influenza Detections

In week 07, the overall percentage of tests positive for influenza was 33% The percentage of tests positive for influenza A continued to decline slowly. The percentage of tests positive for influenza B continued to increase to 17% in week 07. For the first time this season, detections of influenza B were greater than those of influenza A.

The percentage of influenza A detections for week 07 are below average but remain within the expected range for this time of year. The percentage of tests positive for influenza B in week 07 continues to be well above expected levels for this time of year. For data on other respiratory virus detections, see the 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 period 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, weeks 2017-35 to 2018-07

Report Week	A(Unsubtyped)	A(H3)	A(H1)pdm09	Influenza B
35	3	20	6	5
36	7	28	1	3
37	7	14	13	4
38	18	31	3	5
39	18	53	1	8
40	24	41	1	5
41	32	50	0	11
42	27	73	1	15
43	44	107	3	21
44	52	114	3	30
45	71	153	7	47
46	113	187	13	75
47	157	272	13	112
48	259	417	33	190
49	370	544	16	274
50	523	633	16	473
51	800	864	51	719
52	1105	856	33	1008
1	1836	925	60	1539
2	1987	808	49	1730
3	1649	870	80	1912
4	1675	632	57	1802
5	1664	542	54	2125
6	1823	502	49	2383
7	1887	305	52	2394

To date this season, 42,773 laboratory-confirmed influenza detections have been reported, of which 60% have been influenza A. Influenza A(H3N2) has been the most common subtype detected this season, representing 94% of subtyped 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 - Text Description

Figure 3 - Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, weeks 2017-35 to 2018-07

Reporting provincesTable Figure 3 - Footnote 1	Week (February 11, 2018 to February 17, 2018)					Cumulative (August 27, 2017 to February 17, 2018)
	Influenza A				B	Influenza A				B	A & B Total
	A Total	A (H1)pdm09	A (H3)	A(UnS)Table Figure 3 - Footnote 3	B Total	A Total	A (H1)pdm09	A (H3)	A(UnS)Table Figure 3 - Footnote 3	B Total
BC	76	24	43	9	102	1810	296	1166	348	2000	3810
AB	76	8	48	20	167	5281	113	3862	1306	2452	7733
SK	33	1	13	19	88	1558	42	1082	434	898	2456
MB	18	0	3	15	55	1068	7	349	712	217	1285
ON	476	12	154	310	424	3922	138	2154	1630	3093	7015
QC	1,365	0	0	1,365	1,376	10594	0	0	10594	7434	18028
NB	97	4	18	75	70	890	6	165	719	414	1304
NS	27	0	0	27	20	290	0	0	290	112	402
PE	3	0	3	0	13	67	3	64	0	111	178
NL	40	0	0	40	43	160	0	3	157	118	278
YT	3	0	2	1	0	59	5	37	17	39	98
NT	3	2	1	0	1	126	4	122	0	23	149
NU	3	1	2	0	0	35	2	33	0	2	37
Canada	2220	52	287	1881	2359	25860	616	9037	16207	16913	42773
PercentageTable Figure 3 - Footnote 2	48%	2%	13%	85%	52%	60%	2%	35%	63%	40%	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 3 Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available. Return to first Table Figure 3 - Footnote 3 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 34,733 laboratory-confirmed influenza cases (Table 1). Adults 65 years of age and older represent the largest proportion of cases overall (48%), and among cases of influenza A(H3N2) (54%) and influenza B (44%). Adults aged 20-64 represent 33% of cases overall and 31% of influenza A(H3N2) and 35% of influenza B cases. Although much smaller in numbers (548), the majority of influenza A(H1N1) cases are among adults less than 65 years of age, with adults aged 20-64 and children 0-19 years accounting for 53% and 34% of cases respectively.

Table 1 - Weekly and cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reporting, Canada, weeks 2017-35 to 2018-07

Age groups (years)	Cumulative (August 27, 2017 to February 17, 2018)
	Influenza A				B	Influenza A and B
	A Total	A(H1) pdm09	A(H3)	A (UnS)Table 1 Footnote 1	Total	#	%
0-4	2073	106	604	1363	877	2950	8%
5-19	1761	82	652	1027	1845	3606	10%
20-44	3318	151	1266	1901	1807	5125	15%
45-64	3537	137	1401	1999	2778	6315	18%
65+	10953	72	4600	6281	5784	16737	48%
Total	21642	548	8523	12571	13091	34733	100%
Table 1 Footnote 1 UnS: unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available. Return to table 1 footnote 1 referrer

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 07, 4.5% of visits to healthcare professionals were due to influenza-like illness (ILI); an increase compared to the previous week, and above the 5-year average.

The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2012-13 to 2017-18

Figure 4 - Text Description

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2017-35 to 2018-07

Report week	2017-18	Average	Min	Max
35	0.4%	0.8%	0.5%	1.2%
36	0.5%	0.8%	0.7%	1.0%
37	0.7%	0.9%	0.7%	1.0%
38	0.7%	1.1%	1.0%	1.4%
39	1.1%	1.1%	0.9%	1.4%
40	1.3%	1.3%	0.9%	1.6%
41	1.7%	1.4%	0.9%	2.4%
42	1.2%	1.4%	1.0%	1.9%
43	1.6%	1.3%	1.0%	1.5%
44	1.5%	1.3%	0.9%	1.6%
45	1.8%	1.3%	1.2%	1.5%
46	1.7%	1.6%	1.0%	2.0%
47	2.2%	1.5%	1.1%	1.9%
48	2.8%	1.6%	0.8%	2.1%
49	1.7%	1.5%	1.0%	2.5%
50	2.2%	2.3%	1.3%	3.7%
51	2.6%	2.5%	1.6%	4.1%
52	4.0%	4.5%	1.7%	7.1%
1	4.4%	3.7%	1.7%	5.2%
2	2.8%	3.0%	1.1%	4.5%
3	2.8%	2.5%	1.3%	3.6%
4	3.1%	2.4%	1.7%	3.5%
5	4.1%	2.7%	2.0%	4.4%
6	3.6%	2.7%	2.1%	3.3%
7	4.5%	2.4%	1.7%	3.0%

Participatory Syndromic Surveillance

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

In week 07, 1,467 participants reported to FluWatchers, of which 4% reported symptoms of cough and fever, and 20% of these consulted a healthcare professional. Among participants who reported cough and fever, 76% reported days missed from work or school, resulting in a combined total of 140 missed days of work or school.

Table 2 - Summary of influenza-like illness symptoms reported by participating Canadians, Canada, week 2018-07

Number of Participants Reporting	Percentage participants reporting Cough and Fever	Percentage of participants with cough and fever who consulted a healthcare professional	Percentage of participants with cough and fever who reported missed days from work or school	Number of missed days from work or school
1467	4%	20%	76%	140

Influenza Outbreak Surveillance

In week 07, the number of reported laboratory-confirmed outbreaks of influenza decreased compared to the previous week.In week 07, 94 new influenza outbreaks were reported: 55 in long-term care facilities, 11 in hospitals, and 28 in other settings. In addition, four ILI outbreaks were reported schools. Among the 88 outbreaks with influenza type/subtype reported, 47 (53%) were associated with influenza B, 33 (38%) were associated with influenza A and eight outbreaks were associated with a mix of influenza A and B (9%).

To date this season, 1,228 influenza/ILI outbreaks have been reported, of which 729 (60%) occurred in LTC facilities. Among the 1,070 outbreaks for which the influenza type/subtype was reported, 601 (56%) were associated with influenza A and 415 (39%) were associated with influenza B, and 54 (5%) were associated with a mix of A and B. Compared to recent influenza A(H3N2) seasons at week 07, the number of cumulative outbreaks reported this season has been greater than during the 2016-17 season and lower compared to the 2014-15 season.

Figure 5 - Text Description

Figure 5 - Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2017-35 to 2018-07

Report week	Hospitals	Long Term Care Facilities	Other
35	0	0	0
36	0	1	0
37	0	0	0
38	0	2	0
39	0	1	1
40	1	0	0
41	0	0	1
42	0	2	1
43	3	1	1
44	0	1	0
45	3	1	4
46	0	2	5
47	0	2	5
48	9	11	7
49	4	14	12
50	9	31	16
51	11	48	28
52	5	72	23
1	12	110	38
2	18	99	48
3	14	84	45
4	13	63	24
5	9	54	19
6	10	75	31
7	11	55	28

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 07, 46 influenza-associated hospitalizations were reported by participating provinces and territories1.  To date this season, 3,451 influenza-associated hospitalizations have been reported, 77% of which were associated with influenza A, and 2,357 cases (68%) were in adults 65 years of age or older. To date, 317 ICU admissions and 163 deaths have been reported.

Figure 6 - Text Description

Figure 6 - Cumulative numbers of hospitalizations by age-group reported by participating provinces and territories, weeks 2017-35 to 2018-07

Age Group	Total
0-4 yr	200
5-19 yr	131
20-44 yr	212
45-64 yr	551
65+ yr	2357

Figure 6 note 1

Influenza-associated hospitalizations are reported by NL, PE, NS, NB, MB, AB, YT and NT. Only hospitalizations that require intensive medical care are reported by SK.

Return to figure 6 note 1 referrer

Pediatric Influenza Hospitalizations and Deaths

In week 07, the number of laboratory-confirmed influenza-associated pediatric (≤16 years of age) hospitalizations reported by the Immunization Monitoring Program Active (IMPACT) network increased compared to the previous week. In week 07, 89 hospitalizations were reported of which 52 (60%) were due to influenza A. The number of weekly hospitalizations has been above the seven-season average since week 45.

To date this season, 686 pediatric hospitalizations have been reported by the IMPACT network, 431 (63%) of which were associated with influenza A. Children 0-23 months  accounted for the largest proportion of influenza A hospitalizations (39%). Among the 255 hospitalizations due to influenza B, children 5-9 years accounted for the largest proportion of cases (30%).

Additionally, 114 ICU admissions and six deaths have been reported to date. Children aged 0-23 months and 10-16 years each accounted for 27% of ICU cases. Among the ICU cases with available information, 65% were due to influenza A and approximately 43% had no reported previous or concurrent medical conditions.

Figure 7 - Text Description

Figure 7 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by type and age-group reported by the IMPACT network, Canada, weeks 2017-35 to 2018-07

Age Group	Total
0-5 mo	74
6-23 mo	156
2-4 yr	179
5-9 yr	159
10-16 yr	118

Figure 8 - Text Description

Figure 8 - Number of pediatric hospitalizations (≤16 years of age) with influenza reported by the IMPACT network, by week, Canada, weeks 2017-35 to 2018-07

Report Week	2017-2018	Average	Min	Max
35	0	0	0	0
36	1	0	0	1
37	0	0	0	2
38	1	0	0	2
39	2	1	0	3
40	0	0	0	2
41	3	1	0	2
42	1	1	0	4
43	7	1	0	3
44	1	3	1	6
45	4	3	2	4
46	8	5	1	13
47	13	4	0	9
48	16	9	2	23
49	23	15	3	28
50	26	23	4	47
51	39	32	4	72
52	60	47	7	92
1	57	40	5	75
2	39	35	4	62
3	50	38	4	67
4	93	35	7	47
5	67	40	11	59
6	79	38	15	79
7	89	40	17	120

Figure 8 Footnote 1

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2010-11 to 2017-18

Return to figure 8 note 1 referrer

Influenza Strain Characterizations

During the 2017-18 influenza season, the National Microbiology Laboratory (NML) has characterized 1,701 influenza viruses [895 A(H3N2), 86 A(H1N1)pdm09 and 720 B viruses] that were received from Canadian laboratories.

Antigenic Characterization

Among influenza viruses characterized by hemagglutination inhibition assay during the 2017-18 season, most viruses were antigenically similar to the cell-culture propagated reference strains recommended by WHO.

Table 3 - Influenza antigenic strain characterizations, Canada, weeks 2017-35 to 2018-07

Strain Characterization Results	Count	Description
Influenza A (H3N2)
A/Hong Kong/4801/2014-like	166	Viruses antigenically similar to A/Hong Kong/4801/2014, the A(H3N2) component of the 2017-18 Northern Hemisphere's trivalent and quadrivalent vaccine.
Reduced titer to A/Hong Kong/4801/2014	18	These A(H3N2) viruses reacted poorly with antisera raised against cell-propagated A/Hong Kong/4801/2014, suggesting some antigenic differences.
Influenza A (H1N1)
A/Michigan/45/2015-like	86	Viruses antigenically similar to A/Michigan/45/2015, the A(H1N1) component of the 2017-18 Northern Hemisphere's trivalent and quadrivalent influenza vaccine.
Influenza B
B/Brisbane/60/2008-like (Victoria lineage)	7	Viruses antigenically similar to B/Brisbane/60/2008. B/Brisbane/60/2008 is the influenza B component of the 2017-18 Northern Hemisphere's trivalent and quadrivalent influenza vaccine.
Reduced titer to B/Brisbane/60/2008 (Victoria lineage)	24	These B/Victoria lineage viruses reacted poorly with antisera raised against cell-propagated B/Brisbane/60/2008, suggesting some antigenic differences.
B/Phuket/3073/2013-like (Yamagata lineage)	689	Viruses antigenically similar to B/Phuket/3073/2013, the additional influenza B component of the 2017-18 Northern Hemisphere quadrivalent influenza vaccine.

Genetic Characterization of A(H3N2) viruses

During the 2017-18 season, 711 A(H3N2) viruses did not grow to sufficient titers for antigenic characterization by HI assay. Therefore, genetic characterization was performed to determine to which genetic group they belong. Sequence analysis showed that 632 A(H3N2) viruses belonged to genetic group 3C.2a, 77 viruses belonged to subclade 3C.2a1 and two viruses belonged to the clade 3C.3a.

Additionally, of the 184 influenza A(H3N2) viruses that were characterized antigenically as similar to A/Hong Kong/4801/2014, 144 belonged to genetic group 3C.2a and 16 viruses belonged to subclade 3C.2a1. The 18 viruses that showed reduced titer to A/Hong Kong/4801/2014 belonged to genetic clade 3C.3a. Sequencing is pending for the six remaining virus isolates.

A/Hong Kong/4801/2014-like virus belongs to genetic group 3C.2a and is the influenza A/H3N2 component of the 2017-18 Northern Hemisphere influenza vaccine.

Genetic Characterization of Influenza B viruses

Among the viruses characterized antigenically as having reduced titer to ferret antisera produced against cell-propagated B/Brisbane/60/2008, sequence analysis showed that all 22 viruses had a two amino acid deletion in the HA gene. Sequencing is pending for the two remaining virus isolates.

Antiviral Resistance

During the 2017-18 season, the National Microbiology Laboratory (NML) has tested 790 influenza viruses for resistance to oseltamivir and 786 viruses for resistance to zanamivir. All but one of the A(H1N1) viruses were sensitive to oseltamivir and all but one influenza B viruses were sensitive to zanamivir (Table 4).

Table 4 - Antiviral resistance by influenza virus type and subtype, Canada, weeks 2017-35 to 2018-07

Virus type and subtype	Oseltamivir		Zanamivir
	# tested	# resistant (%)	# tested	# resistant (%)
A (H3N2)	401	0 (0%)	397	0 (0%)
A (H1N1)	67	1 (1.5%)	67	0 (0%)
B	322	0 (0%)	322	1 (0.3%)
TOTAL	790	1 (0.1%)	786	1 (0.1%)
Note: Since the 2009 pandemic, all circulating influenza A viruses have been resistant to amantadine, and it is therefore not currently recommended for use in the treatment of influenza. During the 2017-18 season, the subset of influenza A viruses that were tested for resistance to amantadine were resistant.

Provincial and International Influenza Reports

FluWatch Surveillance System Description and Definitions, 2017-18

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. For a description of FluWatch surveillance components and definitions, see System Description and Definitions.

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).

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