FluWatch report: February 17 to 23, 2019 (Week 08)

Figure 1 - Text equivalent

Province	Influenza Surveillance Region	Activity Level
N.L.	Eastern	Localized
N.L.	Labrador-Grenfell	Localized
N.L.	Central	Localized
N.L.	Western	Sporadic
P.E.I.	Prince Edward Island	Sporadic
N.S.	Zone 1 - Western	Sporadic
N.S.	Zone 2 - Northern	Localized
N.S.	Zone 3 - Eastern	Localized
N.S.	Zone 4 - Central	Localized
N.B.	Region 1	Sporadic
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	Localized
Que.	Centre-du-Québec	Sporadic
Que.	Montréal et Laval	Localized
Que.	Ouest-du-Québec	Localized
Que.	Montérégie	Localized
Ont.	Central East	Localized
Ont.	Central West	Localized
Ont.	Eastern	Localized
Ont.	North East	Sporadic
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	Sporadic
Alta.	South Zone	Localized
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 08, the following results were reported from sentinel laboratories across Canada (Figures 2 and 3):

• The percentage of tests positive for influenza was 17.9%.
• A total 1,535 laboratory detections of influenza were reported, of which 98% were influenza A.
• Influenza  A(H1N1)pdm09 and A(H3N2) accounted for equal proportions of subtyped influenza A detections.
• Detections of influenza A(H3N2) have been steadily increasing, from 93 detections in week 4 (mid-January) to 199 this week.

To date this season, 32,429 laboratory-confirmed influenza detections have been reported:

• 99% have been influenza A.
• Among the 11,210 influenza A viruses subtyped, 89% 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 25,393 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.
• 61% 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	1234	118	315	42
7	1091	123	234	31
8	1105	199	200	39

Figure 3 - Text equivalent

Reporting provincesTable Figure 3 - Footnote 1	Week (February 17, 2019 to February 23, 2019)					Cumulative (August 26, 2018 to February 23, 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	300	83	101	116	5	3678	2473	329	876	33	3711
AB	72	28	27	17	10	5382	3485	178	1719	74	5456
SK	0	0	0	0	0	2173	1349	60	764	10	2183
MB	12	0	2	10	0	994	270	8	716	6	1000
ON	268	67	66	135	4	4119	1800	637	1682	81	4200
QC	594	0	0	594	15	12544	0	0	12544	240	12784
NB	136	14	2	120	0	1967	197	15	1755	2	1969
NS	76	0	0	76	2	336	0	0	336	6	342
PEI	2	2	0	0	0	185	185	0	0	0	185
NL	32	0	0	32	0	357	1	0	356	2	359
YT	5	3	0	2	0	68	50	1	17	0	68
N.W.T	1	1	0	0	0	153	151	2	0	0	153
NU	1	1	0	0	0	19	19	0	0	0	19
Canada	1499	199	198	1102	36	31975	9980	1230	20765	454	32429
PercentageTable Figure 3 - Footnote 2	98%	13%	13%	74%	2%	99%	31%	4%	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 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 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 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 2019-08

Age groups (years)	Cumulative (August 26, 2018 to February 23, 2019)
	Influenza A				B	Influenza A and B
	A Total	A(H1) pdm09	A(H3)	A (UnS)Footnote 1	Total	#	%
0-4	5452	1570	42	3840	62	5514	22%
5-19	3724	1300	58	2366	70	3794	15%
20-44	5064	1699	139	3226	55	5119	20%
45-64	5018	1597	139	3282	49	5067	20%
65+	5755	1110	596	4049	144	5899	23%
Total	25013	7276	974	16763	380	25393	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 08, 1.2% 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	0.9%	2.7%	2.1%	3.5%
7	0.9%	2.7%	1.9%	3.4%
8	1.2%	2.6%	2.1%	3.1%

Participatory Syndromic Surveillance

In week 08, 2,131 participants reported to FluWatchers, of which 53 (2.5%) reported symptoms of cough and fever (Figure 5).

Among the 53 participants who reported fever and cough:

• 9% consulted a healthcare professional;
• 74% reported days missed from work or school, resulting in a combined total of 102 missed days of work or school.

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%
8	2.5%

Influenza Outbreak Surveillance

In week 08, 37 new laboratory-confirmed influenza outbreaks were reported: long-term care facilities (LTCF) (20), acute care facilities (4), schools and daycares (4) and other settings (9). Two new ILI outbreaks in long-term care facilities were also reported in week 08.

To date this season, 446 laboratory-confirmed influenza outbreaks have been reported (Figure 6):

• 269 (60%) outbreaks were in LTCF, 27 were in schools, 61 in acute care facilities, and 89 were in other settings.
• Among the 408 outbreaks for which the influenza type was available, 99% (402) were associated with influenza A.
• Among the 177 outbreaks for which the influenza A subtype was available, 63% (112) were associated with influenza A(H1N1)pdm09;

To date this season, 107 ILI outbreaks have been reported; 56 occurred in LTCF, 47 in schools, and four 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	20	8	0	0
6	8	20	6	0	0
7	6	18	5	0	0
8	4	20	9	4	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 2,093 influenza-associated hospitalizations have been reported by participating provinces and territories^{Footnote 1}.

Hospitalizations (Table 2):

• 99.6% (2,085) 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 384 ICU admissions and 93 deaths have been reported.
  • 42% (163) 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 2019-08

Age Groups (years)	Cumulative (August 26, 2018 to February 23, 2019)
	Influenza A	Influenza B	Rate per 100,000 population
0-4	316	2	66.81
5-19	179	2	13.04
20-44	287	0	10.09
45-64	581	1	26.74
65+	722	3	59.59
Total	2085	8
%	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 08, 43 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, 928 pediatric hospitalizations have been reported (Figure 8):

• 69% of cases were in children under 5 years of age.
• 98% (914) of cases have been associated with influenza A.
• Among the 295 cases for which the influenza subtype was available, 280 (95%) were associated with A(H1N1)pdm09.

To date this season, 159 ICU admissions, and 10 deaths have been reported.

• 63% (101) of ICU admissions were in children under 5 years of age.
• All but two 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	47	9	2	23
49	39	15	3	28
50	51	23	4	47
51	85	32	4	72
52	89	47	7	92
1	93	40	5	75
2	60	35	4	62
3	70	38	4	67
4	60	35	7	47
5	51	40	11	59
6	48	38	15	79
7	44	40	17	120
8	43	47	25	139

Figure 8 - Text equivalent

Age Group	Total
0-5 mo	94
6-23 mo	238
2-4 yr	305
5-9 yr	204
10-16 yr	87

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, 590 hospitalizations, 65 ICU admissions and 22 deaths have been reported (Figure 9):

• 543 (92%) hospitalizations were associated with influenza A.
• A greater proportion of hospitalizations have been reported among  adults ≥65 years of age (58%) compared to adults <65 years of age (42%).
• 84% of hospitalized cases reported more than one type of comorbid condition.  
• The most commonly reported comorbidity was endocrine disorders, which were reported in 80% of hospitalized cases.

Figure 9 - Text equivalent

Age Group	Total
20-34 yr	57
35-49 yr	58
50-64 yr	134
65-79 yr	172
80+ yr	169

Influenza Strain Characterizations

Since September 1, 2018, the National Microbiology Laboratory (NML) has characterized 1,412 influenza viruses (150 A(H3N2), 1,234 A(H1N1) and 28 B) that were received from Canadian laboratories. 

Genetic Characterization of Influenza A(H3N2):

79 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:

• 15 viruses belonged to genetic group 3C.2a.
• 63 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):

• 55 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.
• 16 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.
• 33 influenza A(H3N2) viruses characterized belonged to genetic group 3C.2a1. 15 viruses belonged to genetic group 3C.2a and 11 to 3C.3a. Sequencing is pending for the remaining isolates.

Influenza A(H1N1):

• 1,201 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.
• 33 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).

• Nine 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.
• Two viruses 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:

356 influenza A (51 A(H3N2) and 305 A(H1N1)) viruses were tested for resistance to amantadine and it was found that:

• All 356 influenza A viruses were resistant to amantadine.

Antiviral Resistance – Oseltamivir:

842 influenza viruses (76 A(H3N2), 740 A(H1N1) and 26 B) were tested for resistance to oseltamivir and it was found that:

• All 76 A(H3N2) viruses were sensitive to oseltamivir.
• Of the 740 A(H1N1) viruses tested, 738 were sensitive to oseltamivir and two viruses were resistant to oseltamivir with a H275Y mutation.
• All 26 B viruses were sensitive to oseltamivir.

Antiviral Resistance – Zanamivir:

841 influenza viruses (76 A(H3N2), 739 H1N1 and 26 B) were tested for resistance to zanamivir and it was found that:

• All 841 influenza viruses were sensitive to zanamivir.