FluWatch report: February 10 to 16, 2019 (Week 07)

Figure 1 - Text equivalent

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

Laboratory-Confirmed Influenza Detections

In week 07, the following results were reported from sentinel laboratories across Canada (Figures 2 and 3):

• The percentage of tests positive for influenza was similar to the previous week at 17.9%.
• A total 1,565 laboratory detections of influenza were reported, of which 98% were influenza A.

To date this season, 30,981 laboratory-confirmed influenza detections have been reported:

• 99% have been influenza A.
• Among the 10,778 influenza A viruses subtyped, 91% have been A(H1N1)pdm09.
• Influenza B often circulates later in the season in Canada (Feb-Apr). Fewer influenza B detections have been reported this season compared to recent seasons at this time of year.

To date this season, detailed information on age and type/subtype has been received for 24,187 laboratory-confirmed influenza cases (Table 1):

• 85% 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 equivalent

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	1985	93	1061	43
3	1613	101	585	40
4	1483	93	532	48
5	1449	112	433	43
6	1241	113	313	42
7	1205	109	220	31

Figure 3 - Text equivalent

Reporting provincesTable Figure 3 - Footnote 1	Week (February 10, 2019 to February 16, 2019)					Cumulative (August 26, 2018 to February 16, 2019)
	Influenza A				B	Influenza A				B	A & B Total
	A Total	A (H1N1)pdm09	A (H3N2)	A(UnS)Table Figure 3 - Footnote 3	B Total	A Total	A (H1N1)pdm09	A (H3N2)	A(UnS)Table Figure 3 - Footnote 3	B Total
BC	195	52	21	122	5	3481	2386	220	875	28	3509
AB	60	26	17	17	9	5309	3457	151	1701	64	5373
SK	6	3	1	2	1	2173	1349	60	764	10	2183
MB	11	4	0	7	0	982	270	6	706	6	988
ON	315	96	69	150	4	3839	1723	560	1556	77	3916
QC	734	0	0	734	10	11949	0	0	11949	225	12174
NB	110	23	0	87	0	1831	183	13	1635	2	1833
NS	58	0	0	58	1	260	0	0	260	4	264
PEI	11	11	0	0	0	183	183	0	0	0	183
NL	26	0	0	26	0	325	1	0	324	2	327
YT	5	2	0	3	0	63	47	1	15	0	63
N.W.T	0	0	0	0	0	151	149	2	0	0	151
NU	1	1	0	0	0	17	17	0	0	0	17
Canada	1532	218	108	1206	30	30563	9765	1013	19785	418	30981
PercentageTable Figure 3 - Footnote 2	98%	14%	7%	79%	2%	99%	32%	3%	65%	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 2019-07

Age groups (years)	Cumulative (August 26, 2018 to February 16, 2019)
	Influenza A				B	Influenza A and B
	A Total	A(H1) pdm09	A(H3)	A (UnS)Footnote 1	Total	#	%
0-4	5269	1552	36	3681	54	5323	22%
5-19	3575	1284	38	2253	63	3638	15%
20-44	4859	1655	110	3094	49	4908	20%
45-64	4808	1541	118	3149	48	4856	20%
65+	5327	1062	487	3778	135	5462	23%
Total	23838	7094	789	15955	349	24187	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 07, 1.1% of visits to healthcare professionals were due to influenza-like illness (ILI) (Figure 4). The percentage of visits for ILI is low compared to previous seasons.

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 equivalent

Surveillance 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%
1	2.8%	3.8%	1.8%	5.6%
2	1.8%	2.6%	1.3%	3.9%
3	1.1%	2.5%	1.4%	3.6%
4	1.3%	2.5%	1.6%	3.1%
5	1.4%	2.6%	1.9%	4.0%
6	1.0%	2.7%	2.1%	3.5%
7	1.1%	2.7%	1.9%	3.4%

Participatory Syndromic Surveillance

In week 07, 2,131 participants reported to FluWatchers, of which 57 (2.7%) reported symptoms of cough and fever (Figure 5).

Among the 57 participants who reported fever and cough:

• 19% consulted a healthcare professional;
• 68% reported days missed from work or school, resulting in a combined total of 102 missed days of work or school.
• 69% reported having been vaccinated for influenza this season.

Figure 5 - Text equivalent

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%
1	3.4%
2	2.8%
3	2.5%
4	2.9%
5	3.0%
6	2.6%
7	2.7%

Influenza Outbreak Surveillance

In week 07, 21 new laboratory-confirmed influenza outbreaks were reported: long-term care facilities (LTCF) (13), acute care facilities (4), and other settings (4). Four new ILI outbreaks in schools/daycares were also reported in week 07. The number of new outbreaks reported each week continues to decline from the peak in week 01.

To date this season, 398 laboratory-confirmed influenza outbreaks have been reported (Figure 6):

• 244 (61%) outbreaks were in LTCF, 23 were in schools, 52 in acute care facilities, and 79 were in other settings.
• Among the 369 outbreaks for which the influenza type was available 98% (363) were associated with influenza A.
• Among the 163 outbreaks for which the influenza A subtype was available, 67% (110) were associated with influenza A(H1N1)pdm09;

To date this season, 94 ILI outbreaks have been reported; 44 occurred in LTCF, 47 in schools, and three in acute care facilities.

Figure 6 - Text equivalent

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	8	5	4	0
51	3	12	4	2	0
52	4	24	5	0	0
1	5	40	11	0	0
2	8	38	7	0	0
3	3	26	10	0	0
4	6	17	10	1	0
5	4	21	8	0	0
6	5	19	6	0	0
7	4	13	4	0	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 2,004 influenza-associated hospitalizations have been reported by participating provinces and territories^{Footnote 1}.

Hospitalizations (Table 2):

• 99.7% (1,997) 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 368 ICU admissions and 87 deaths have been reported.
  • 43% (157) of reported ICU admissions were in adults aged 45-64 years.
  • All the ICU admissions, and all but one of the 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 2019-07

Age Groups (years)	Cumulative (August 26, 2018 to February 16, 2019)
	Influenza A	Influenza B	Rate per 100,000 population
0-4	307	2	64.92
5-19	177	1	12.83
20-44	274	0	9.63
45-64	558	1	25.69
65+	681	3	56.22
Total	1997	7
%	99.7%	0.3%
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 07, 44 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, 884 pediatric hospitalizations have been reported (Figure 8):

• 69% of cases were in children under 5 years of age.
• 99% (874) of cases have been associated with influenza A.
• Among the 290 cases for which the influenza subtype was available, 276 (95%) were associated with A(H1N1)pdm09.

To date this season, 147 ICU admissions, and 10 deaths have been reported.

• 63% (93) of ICU admissions were in children under 5 years of age.
• All but one of the 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 equivalent

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	5	1	0	4
43	11	1	0	3
44	15	3	1	6
45	37	3	2	4
46	41	5	1	13
47	36	4	0	9
48	46	9	2	23
49	39	15	3	28
50	51	23	4	47
51	85	32	4	72
52	89	47	7	92
1	94	40	5	75
2	59	35	4	62
3	70	38	4	67
4	61	35	7	47
5	51	40	11	59
6	48	38	15	79
7	44	40	17	120

Figure 8 - Text equivalent

Age Group	Total
0-5 mo	89
6-23 mo	231
2-4 yr	287
5-9 yr	196
10-16 yr	81

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, 538 hospitalizations, 59 ICU admissions and 18 deaths have been reported (Figure 9):

• 493 (92%) hospitalizations were associated with influenza A.
• A greater proportion of hospitalizations have been reported among adults ≥65 years of age (57.3%) compared to adults <65 years of age (42.8%).
• Hospitalizations among adults peaked in week 01 then declined to week 04, and have increased in weeks 05 to 07.
• Among hospitalized cases with available information (481), the most commonly reported comorbidity was endocrine disorders, which were reported in 78% of hospitalized cases. However, 84% of cases reported more than one type of comorbid condition.

Figure 9 - Text equivalent

Age Group	Total
20-34 yr	53
35-49 yr	57
50-64 yr	120
65-79 yr	158
80+ yr	150

Influenza Strain Characterizations

Since September 1, 2018, the National Microbiology Laboratory (NML) has characterized 1,287 influenza viruses (119 A(H3N2), 1,142 A(H1N1) and 26 B) that were received from Canadian laboratories.

Genetic Characterization of Influenza A(H3N2):

61 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:

• 10 viruses belonged to genetic group 3C.2a.
• 50 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):

• 43 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.
• 15 viruses showed reduced titer with ferret antisera 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.
• 27 influenza A(H3N2) viruses characterized belonged to genetic group 3C.2a1. Nine viruses belonged to genetic group 3C.2a and nine to 3C.3a. Sequencing is pending for the remaining isolates.

Influenza A(H1N1):

• 1,112 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.
• 30 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).

• Eight 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.
• One virus showed reduced titer with ferret antisera raised against cell culture-propagated B/Colorado/06/2017.
• 17 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:

351 influenza A (51 A(H3N2) and 300 A(H1N1)) viruses were tested for resistance to amantadine and it was found that:

• All 351 influenza A viruses were resistant to amantadine.

Antiviral Resistance – Oseltamivir:

793 influenza viruses (71 A(H3N2), 697 A(H1N1) and 25 B) were tested for resistance to oseltamivir and it was found that:

• All 71 A(H3N2) viruses were sensitive to oseltamivir.
• Of the 697 A(H1N1) viruses tested, 696 were sensitive to oseltamivir and one virus was resistant to oseltamivir with a H275Y mutation.
• All 25 B viruses were sensitive to oseltamivir.

Antiviral Resistance – Zanamivir:

794 influenza viruses (71 A(H3N2), 698 H1N1 and 25 B) were tested for resistance to zanamivir and it was found that:

• All 794 influenza viruses were sensitive to zanamivir.