FluWatch report: January 13, 2019 to January 19, 2019 (week 03)

Figure 1 - Text description

Province	Influenza Surveillance Region	Activity Level
N.L.	Eastern	Sporadic
N.L.	Labrador-Grenfell	Localized
N.L.	Central	Localized
N.L.	Western	Sporadic
P.E.I.	Prince Edward Island	Localized
N.S.	Zone 1 - Western	Localized
N.S.	Zone 2 - Northern	Localized
N.S.	Zone 3 - Eastern	Localized
N.S.	Zone 4 - Central	Localized
N.B.	Region 1	Localized
N.B.	Region 2	Localized
N.B.	Region 3	Localized
N.B.	Region 4	Sporadic
N.B.	Region 5	Sporadic
N.B.	Region 6	Localized
N.B.	Region 7	Localized
Que.	Nord-est	Localized
Que.	Québec et Chaudieres-Appalaches	Sporadic
Que.	Centre-du-Québec	Localized
Que.	Montréal et Laval	Localized
Que.	Ouest-du-Québec	Sporadic
Que.	Montérégie	Localized
Ont.	Central East	Localized
Ont.	Central West	Localized
Ont.	Eastern	Localized
Ont.	North East	Localized
Ont.	North West	No Activity
Ont.	South West	Localized
Ont.	Toronto	Localized
Man.	Northern Regional	Sporadic
Man.	Prairie Mountain	Sporadic
Man.	Interlake-Eastern	Sporadic
Man.	Winnipeg	Sporadic
Man.	Southern Health	Sporadic
Sask.	North	Sporadic
Sask.	Central	Sporadic
Sask.	South	Sporadic
Alta.	North Zone	Sporadic
Alta.	Edmonton	Localized
Alta.	Central Zone	Sporadic
Alta.	Calgary	Sporadic
Alta.	South Zone	Sporadic
B.C.	Interior	Sporadic
B.C.	Fraser	Sporadic
B.C.	Vancouver Coastal	Sporadic
B.C.	Vancouver Island	Sporadic
B.C.	Northern	Sporadic
Y.T.	Yukon	No Data
N.W.T.	North	No Activity
N.W.T.	South	Sporadic
Nvt.	Qikiqtaaluk	Sporadic
Nvt.	Kivalliq	Sporadic
Nvt.	Kitimeot	No Activity

Laboratory Confirmed Influenza Detections

In week 03, the following results were reported from sentinel laboratories across Canada (Figure 2):

• The percentage of tests positive for influenza decreased to 20.8% in week 03.
• A total 2,313 laboratory detections of influenza were reported, of which 98% were influenza A.

To date this season 20,753 laboratory-confirmed influenza detections have been reported:

• 99% have been influenza A.
• Among the 7,565 influenza A viruses subtyped, 94% have been A(H1N1)pdm09.
• Provincial and territorial differences in influenza type/subtype distribution are observed (Figure 3).

To date this season, detailed information on age and type/subtype has been received for 18,923 laboratory-confirmed influenza cases (Table 1):

• 86% of all influenza A(H1N1)pdm09 detections have been reported in individuals younger than 65 years of age.
• 62% of all influenza A(H3N2) detections have been reported in adults 65 years of age and older.

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.

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

Surveillance Week	A(Unsubtyped)	A(H3)	A(H1)pdm09	Influenza B
35	3	2	7	0
36	4	7	4	0
37	3	2	3	1
38	6	3	2	3
39	11	5	1	3
40	16	7	29	3
41	27	6	21	3
42	40	19	55	2
43	83	23	128	4
44	169	13	214	6
45	244	18	295	15
46	346	10	404	9
47	449	17	507	8
48	679	29	632	10
49	851	35	785	16
50	1368	35	828	14
51	1890	54	953	21
52	2292	55	903	26
1	2387	58	893	31
2	2032	92	1060	43
3	1701	99	533	40

Figure 3 - Text description

Reporting provincesTable Figure 3 - Footnote 1	Week (January 13 to January 19, 2019)					Cumulative (August 26, 2018 to January 19, 2019)
	Influenza A				B	Influenza A				B	A & B Total
	A Total	A (H1N1)pdm09	A (H3N2)	Table Figure 3 - Footnote Table Figure 3 - Footnote 3	B Total	A Total	A (H1N1)pdm09	A (H3N2)	Table Figure 3 - Footnote Table Figure 3 - Footnote 3	B Total
BC	299	193	13	93	3	1958	1069	77	812	10	1968
AB	94	59	12	23	1	4915	3250	82	1583	33	4948
SK	31	21	1	9	0	2079	1307	55	717	1	2080
MB	59	10	1	48	1	830	211	3	616	3	833
ON	419	165	69	185	7	1893	977	236	680	48	1941
QC	1,051	0	0	1,051	25	7387	0	0	7387	115	7502
NB	214	25	3	186	0	1025	68	3	954	2	1027
NS	17	0	0	17	1	85	0	0	85	1	86
PEI	32	32	0	0	0	58	58	0	0	0	58
NL	52	0	0	52	0	135	1	0	134	1	136
YT	6	6	0	0	0	23	16	1	6	0	23
N.W.T	1	1	0	0	0	142	140	2	0	0	142
NU	0	0	0	0	0	9	9	0	0	0	9
Canada	2275	512	99	1664	38	20539	7106	459	12974	214	20753
Table Figure 3 - Footnote 2	98%	23%	4%	73%	2%	99%	35%	2%	63%	1%	100%
Table Figure 3 - Footnote 1 Specimens from NWT, YT, and Nvt 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.

Table 1 - Cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reporting, Canada, weeks 2018-35 to 2019-03

Age groups (years)	Cumulative (August 26, 2018 to January 19, 2019)
	Influenza A				B	Influenza A and B
	A Total	A(H1) pdm09	A(H3)	A (UnS)Footnote 1	Total	#	%
0-4	4072	1412	22	2638	32	4104	22%
5-19	2884	1198	21	1665	34	2918	15%
20-44	3975	1482	73	2420	26	4001	21%
45-64	3887	1325	85	2477	33	3920	21%
65+	3896	883	334	2679	84	3980	21%
Total	18714	6300	535	11879	209	18923	100%
Table 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

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 03, 1.4% of visits to healthcare professionals were due to influenza-like illness (ILI) (Figure 4). The percentage of visits for ILI is within expected levels.

The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2013-14 to 2017-18

Figure 4 - Text description

Report week	2018-19	Average	Min	Max
35	0.6%	0.6%	0.4%	0.9%
36	0.7%	0.8%	0.5%	1.0%
37	0.6%	0.9%	0.7%	1.1%
38	0.5%	1.0%	0.7%	1.4%
39	1.8%	1.1%	0.8%	1.5%
40	0.6%	1.6%	0.9%	3.4%
41	1.1%	1.6%	1.1%	2.1%
42	1.0%	1.4%	0.8%	1.8%
43	0.9%	1.4%	0.7%	1.8%
44	0.8%	1.4%	1.1%	1.6%
45	1.3%	1.5%	1.2%	1.8%
46	1.3%	1.7%	1.1%	2.2%
47	1.3%	1.6%	1.1%	2.2%
48	1.5%	1.8%	1.0%	2.8%
49	1.6%	1.5%	1.1%	1.8%
50	1.5%	2.1%	1.4%	2.7%
51	1.0%	2.3%	1.6%	3.2%
52	3.2%	3.6%	1.9%	5.0%
01	2.8%	3.8%	1.8%	5.6%
02	1.8%	2.6%	1.3%	3.9%
03	1.4%	2.5%	1.4%	3.6%

Participatory Syndromic Surveillance

In week 03, 2,211 participants reported to FluWatchers, of which 55 (2.5%) reported symptoms of cough and fever (Figure 5).

Among the 55 participants who reported fever and cough:

• 13% consulted a healthcare professional;
• 73% reported days missed from work or school, resulting in a combined total of 108 missed days of work or school.

Figure 5 - Text description

Surveillance week	% cough and fever
40	2.6%
41	2.5%
42	1.7%
43	1.5%
44	1.3%
45	1.7%
46	2.0%
47	1.3%
48	2.4%
49	2.0%
50	3.7%
51	3.9%
52	3.6%
01	3.4%
02	2.8%
03	2.5%

Influenza Outbreak Surveillance

In week 03, 31 new laboratory-confirmed influenza outbreaks were reported: long-term care facilities (LTCF) (19), acute care facilities (3), and other settings (9). Thirteen new ILI outbreaks in long-term care facilities (5) and  schools (8) were also reported in week 03.

To date this season, 254 laboratory-confirmed influenza outbreaks have been reported (Figure 6):

• 148 outbreaks were in LTCF, 22 were in schools, 33 in acute care facilities, and 51 were in other settings.
• Among the 239 outbreaks for which the influenza type was available 99% (236) were associated with influenza A.
• Among the 115 outbreaks for which the influenza A subtype was available:
  • 77% (89) were associated with influenza A(H1N1)pdm09;
  • 23% (26) were associated with A(H3N2),

To date this season, 58 ILI outbreaks have been reported; 38 occurred in LTCF, 17 in schools, and three in acute care facilities.

Figure 6 - Text description

Surveillance Week	Acute Care Facilities	Long Term Care Facilities	Other	Schools and Daycares	Remote and/or Isolated Communities
35	0	0	0	0	0
36	0	0	0	0	0
37	0	0	0	0	0
38	0	0	0	0	0
39	0	0	0	0	0
40	0	2	0	1	0
41	0	0	0	0	0
42	0	1	1	0	0
43	0	3	1	0	0
44	0	1	1	2	0
45	0	2	1	3	0
46	2	5	1	3	0
47	2	4	0	1	0
48	2	6	1	5	0
49	1	2	3	1	0
50	3	7	5	4	0
51	3	10	4	2	0
52	4	24	5	0	0
01	5	34	11	0	0
02	8	28	8	0	0
03	3	19	9	0	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 1,637 influenza-associated hospitalizations have been reported by participating provinces and territories^{Footnote 1}.

Hospitalizations (Table 2):

• 99.6% (1,512) were associated with influenza A
• The highest estimated rate of hospitalization is among children under 5 years of age.

Intensive Care Unit (ICU) cases and deaths:

• To date this season 262 ICU admissions and 56 deaths have been reported.
  • 43% (113) of reported ICU admissions were in adults aged 45-64 years
  • All reported deaths were associated with influenza A.

Table 2 - Cumulative number of hospitalizations by age-group and influenza type, reported by participating provinces and territories^{Footnote 1}, Canada, weeks 2018-35 to 2019-03

Age Groups (years)	Cumulative (August 26, 2018 to January 19, 2019)
	Influenza A	Influenza B	Rate per 100,000 population
0-4	274	3	58.20
5-19	156	0	11.24
20-44	228	0	8.01
45-64	444	0	20.40
65+	529	3	43.73
Total	1631	6
%	99.6%	0.4%
Table 2 - Note 1 Influenza-associated hospitalizations are reported by Alberta, Manitoba, New Brunswick, Newfoundland and Labrador, Northwest Territories, Nova Scotia, Prince Edward Island and Yukon. Only hospitalizations that require intensive medical care are reported by Saskatchewan. The cumulative rate of hospitalizations is calculated using the total population by age-group in participating provinces and territories. Return to Table 2 - Note 1

Pediatric Influenza Hospitalizations and Deaths

In week 03, 68 pediatric (≤16 years of age) hospitalizations with influenza have been reported by the Immunization Monitoring Program Active (IMPACT) network (Figure 7).

To date this season, 677 pediatric hospitalizations have been reported (Figure 8):

• 81% of cases were in children 6 months to 9 years of age.
• 99% (670) of cases have been associated with influenza A.
• Among the 256 cases for which the influenza subtype was available, 250 (98%) were associated with A(H1N1)pdm09.

To date this season, 98 ICU admissions, and 10 deaths have been reported.

• 87% (100) of ICU admissions were in children 6 months to 9 years of age.
• 99% (114) of ICU admissions have been associated with influenza A.
• 80% (8) of deaths occurred in children 2 to 4 years of age.
• All deaths have been associated with influenza A.

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

Figure 7 - Text description

Surveillance week	2018-19	Average	Min	Max
35	0	0	0	0
36	0	0	0	1
37	0	0	0	2
38	0	0	0	2
39	0	1	0	3
40	0	0	0	2
41	1	1	0	2
42	6	1	0	4
43	11	1	0	3
44	20	3	1	6
45	34	3	2	4
46	42	5	1	13
47	33	4	0	9
48	47	9	2	23
49	39	15	3	28
50	51	23	4	47
51	82	32	4	72
52	89	47	7	92
01	93	40	5	75
02	59	35	4	62
03	68	38	4	67

Figure 8 - Text description

Age Group	Total
0-5 mo	73
6-23 mo	184
2-4 yr	218
5-9 yr	149
10-16 yr	53

Adult Influenza Hospitalizations and Deaths

Surveillance of laboratory-confirmed influenza-associated adult (≥16 years of age) hospitalizations by the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) network began on November 1^st for the 2018-19 season.

To date this season, 324 hospitalizations have been reported (Figure 9):

• 299 (92%) were associated with influenza A.
• A similar proportion of hospitalizations are reported among adults <65 years of age and adults ≥65 years of age
• The most commonly reported comorbidity among hospitalized cases was endocrine disorders, which were reported in 68% of hospitalized cases.

Figure 9 - Text description

Age Group	Total
20-34 yr	33
35-49 yr	38
50-64 yr	79
65-79 yr	92
80+ yr	82

Influenza Strain Characterizations

Since September 1, 2018, the National Microbiology Laboratory (NML) has characterized 728 influenza viruses (57 A(H3N2), 654 A(H1N1) and 17 B) that were received from Canadian laboratories. 

Genetic Characterization of Influenza A(H3N2):

40 influenza A(H3N2) viruses did not grow to sufficient hemagglutination titer for antigenic characterization by hemagglutination inhibition (HI) assay. Therefore, NML has performed genetic characterization to determine the genetic group identity of these viruses.

Sequence analysis of the HA gene of the viruses showed that:

• Six viruses belonged to genetic group 3C.2a.
• 33 viruses belonged to subclade 3C.2a1.
• One isolate could not be sequenced.

A/Singapore/INFIMH-16-0019/2016-like virus belongs to genetic group 3C.2a1 and is the influenza A(H3N2) component of the 2018-19 Northern Hemisphere influenza vaccine.

Antigenic Characterization:

Influenza A (H3N2):

• 17 influenza A(H3N2) viruses were antigenically characterized as A/Singapore/INFIMH-16-0019/2016-like by HI testing using antiserum raised against egg-propagated A/Singapore/INFIMH-16-0019/2016.
• A/Singapore/INFIMH-16-0019/2016-like virus is the influenza A(H3N2) component of the 2018-19 Northern Hemisphere influenza vaccine.
• 13 influenza A (H3N2) viruses characterized belonged to genetic group 3C.2a1. Two viruses belonged to genetic group 3C.2a and two to 3C.3a.

Influenza A(H1N1):

• 641 A(H1N1) viruses characterized were antigenically similar to A/Michigan/45/2015, which is the influenza A(H1N1) component of the 2018-19 Northern Hemisphere influenza vaccine.
• 13 viruses showed reduced titer with ferret antisera raised against cell culture-propagated A/Michigan/45/2015

Influenza B:

Influenza B viruses can be divided into two antigenically distinct lineages represented by B/Yamagata/16/88 and B/Victoria/2/87 viruses. The recommended influenza B components for the 2018-19 Northern Hemisphere influenza vaccine are B/Colorado/06/2017 (Victoria lineage) and B/Phuket/3073/2013 (Yamagata lineage).

• Three influenza B viruses were characterized as B/Colorado/06/2017, which belong to the Victoria lineage and are included as an influenza B component of the 2018-19 Northern Hemisphere influenza vaccine
• 14 influenza B viruses were characterized as B/Phuket/3073/2013-like, which belongs to the Yamagata lineage and is included as an influenza B component of the 2018-19 Northern Hemisphere quadrivalent influenza vaccine.

Antiviral Resistance

Antiviral Resistance – Amantadine:

304 influenza A (42 A(H3N2) and 262 A(H1N1)) viruses were tested for resistance to amantadine and it was found that:

• All 304 influenza A viruses were resistant to amantadine.

Antiviral Resistance – Oseltamivir:

539 influenza viruses (48 A(H3N2), 475 A(H1N1) and 16 B) were tested for resistance to oseltamivir and it was found that:

• All 539 influenza viruses were sensitive to oseltamivir

Antiviral Resistance – Zanamivir:

537 influenza viruses (48 A(H3N2), 473 H1N1 and 16 B) were tested for resistance to zanamivir and it was found that:

• All 537 influenza viruses were sensitive to zanamivir.