FluWatch report: November 18, 2018 to November 24, 2018 (Week 47)

Figure 1 - Text description

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

Laboratory Confirmed Influenza Detections

In week 47, the following results were reported from sentinel laboratories across Canada (Figure 2):

• The percentage of tests positive for influenza continued to increase to 15.3% of tests positive.
• The percentage of tests positive for influenza A is higher for this time of year compared to the same period during the previous eight seasons.
• In week 47, 950 laboratory detections of influenza were reported, of which 99% were influenza A.

To date this season 3,176 laboratory-confirmed influenza detections have been reported (Figure 3):

• 92% have been influenza A.
• Among the 1,760 influenza A viruses subtyped, 82% 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 3,155 laboratory-confirmed influenza cases (Table 1):

• 69% of all influenza A(H1N1)pdm09 detections have been reported in individuals younger than 45 years of age.
• 70% 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	345	10	404	9
47	445	17	480	8

Figure 3 - Text description

Reporting provincesTable Figure 3 - Footnote 1	Week (November 18, 2018 to November 24, 2018)					Cumulative (August 26, 2018 to November 24, 2018)
	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	51	30	5	16	0	162	78	41	43	3	165
AB	539	334	8	197	3	1961	1206	39	716	16	1977
SK	38	0	38	0	58	188	0	188	0	187	375
MB	25	15	0	10	0	100	79	3	18	0	100
ON	28	19	2	7	4	150	64	41	45	26	176
QC	137	0	0	137	1	332	0	0	332	11	343
NB	7	1	0	6	0	12	3	0	9	0	12
NS	1	0	0	1	0	7	0	0	7	0	7
PEI	1	1	0	0	0	4	4	0	0	0	4
NL	0	0	0	0	0	3	1	0	2	1	4
YT	0	0	0	0	0	0	0	0	0	0	0
N.W.T	5	5	0	0	0	9	9	0	0	0	9
NU	1	1	0	0	0	4	4	0	0	0	4
Canada	833	406	53	374	66	2932	1448	312	1172	244	3176
PercentageTable Figure 3 - Footnote 2	93%	49%	6%	45%	7%	92%	49%	11%	40%	8%	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 UnS 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 2018-47

Age groups (years)	Cumulative (August 26, 2018 to November 24, 2018)
	Influenza A				B	Influenza A and B
	A Total	A(H1) pdm09	A(H3)	A (UnS)Footnote 1	Total	#	%
0-4	632	377	3	252	5	637	20%
5-19	650	334	5	311	11	661	21%
20-44	797	399	15	383	9	806	26%
45-64	565	285	32	248	7	572	18
65+	465	206	131	128	14	479	15%
Total	3109	1601	186	1322	46	3155	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 47, 1.9% 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	1.1%	1.4%	0.8%	1.8%
43	1.0%	1.4%	0.7%	1.8%
44	0.8%	1.4%	1.1%	1.6%
45	1.5%	1.5%	1.2%	1.8%
46	1.5%	1.7%	1.1%	2.2%
47	1.9%	1.6%	1.1%	2.2%

Participatory Syndromic Surveillance

In week 47, 2,182 participants reported to FluWatchers, of which 29 (1.3%) reported symptoms of cough and fever (Figure 5).

Among the 29 participants who reported fever and cough:

• 28% consulted a healthcare professional;
• 83% reported days missed from work or school, resulting in a combined total of 66 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%

Influenza Outbreak Surveillance

In week 47, five new laboratory-confirmed influenza outbreaks were reported in long-term care (3) and acute care (2) facilities.

To date this season, 36 laboratory-confirmed influenza outbreaks have been reported (Figure 6):

• 19 outbreaks were in LTCF, eight were in schools, and five were in other settings.
• All of the 30 outbreaks for which the influenza type was available were associated with influenza A.
• Among the 21 outbreaks for which the influenza A subtype was available:
  • 17 were associated with influenza A(H1N1)pdm09;
  • Four were associated with A(H3N2);

One new ILI outbreak in a LTCF was reported in week 47.

To date this season, 25 ILI outbreaks have been reported; 23 occurred in LTCF, one in a school, and one in an acute care facility.

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	2	0	0	0
38	0	1	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	2	1	0	0
44	0	1	1	2	0
45	0	2	1	3	0
46	2	5	1	2	0
47	2	3	0	0	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, more than 471 influenza-associated hospitalizations have been reported by participating provinces and territories^{Footnote 1}.

Hospitalizations (Table 2):

• 99% (471) were associated with influenza A
• The highest estimated rates of hospitalization are among children under 5 years of age.

Intensive Care Unit (ICU) cases and deaths:

• To date this season 49 ICU admissions and nine deaths have been reported.

Table 2 – Cumulative number and estimated rate of hospitalizations by age-group reported by participating provinces and territories^{Footnote 1}, Canada, weeks 2018-35 to 2018-47

Age Groups	Cumulative (August 26, 2018 to November 24, 2018)
	Influenza A	Influenza B	Rate per 100,000 population
0-4	95	0	7.77
5-19	64	0	2.31
20-44	72	0	1.20
45-64	115	0	2.39
65+	125	<5	5.18
Total	471	<5
%	99%	1%

Pediatric Influenza Hospitalizations and Deaths

In week 47, 34 pediatric (≤16 years of age) hospitalizations with influenza have been reported by the Immunization Monitoring Program Active (IMPACT) network. Pediatric hospitalizations reported by IMPACT are at levels not normally seen until late December (4-6 weeks earlier than in recent seasons) (Figure 7).

To date this season, 145 pediatric hospitalizations have been reported (Figure 8):

• All but two cases have been associated with influenza A.
• Among the 109 cases for which the influenza subtype was available, 108 were associated with A(H1N1)pdm09.

To date this season, 18 ICU admissions, and no deaths have been reported.

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	19	3	1	6
45	32	3	2	4
46	42	5	1	13
47	34	4	0	9

Figure 8 - Text description

Age Group	Total
0-5 mo	14
6-23 mo	39
2-4 yr	40
5-9 yr	43
10-16 yr	9

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, 17 hospitalizations have been reported, of which 15 were associated with influenza A and 2 with influenza B.

Influenza Strain Characterizations

Since September 1, 2018, the National Microbiology Laboratory (NML) has characterized 101 influenza viruses (11 A(H3N2), 80 A(H1N1) and 10 B) that were received from Canadian laboratories.

Genetic Characterization of Influenza A (H3N2):

Ten 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:

• One virus belonged to genetic group 3C.2a.
• Nine viruses belonged to subclade 3C.2a1.

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):

• One influenza A(H3N2) virus was 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.
• The influenza A (H3N2) virus characterized belonged to genetic group 3C.2a1.

Influenza A(H1N1):

• 80 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.

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).

• Ten 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:

95 influenza A (18 A(H3N2) and 77 A(H1N1)) viruses were tested for resistance to amantadine and it was found that:

• All 95 influenza A viruses were resistant to amantadine.

Antiviral Resistance – Oseltamivir:

102 influenza viruses (16 A(H3N2), 76 A(H1N1) and 10 B) were tested for resistance to oseltamivir and it was found that:

• All influenza viruses were sensitive to oseltamivir

Antiviral Resistance – Zanamivir:

102 influenza viruses (16 A(H3N2), 76 H1N1 and 10 B) were tested for resistance to zanamivir and it was found that:

• All influenza viruses were sensitive to zanamivir.