FluWatch report: December 2, 2018 to December 8, 2018 (Week 49)

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	No Activity
N.B.	Region 1	Localized
N.B.	Region 2	No Activity
N.B.	Region 3	Sporadic
N.B.	Region 4	No Activity
N.B.	Region 5	Sporadic
N.B.	Region 6	No Activity
N.B.	Region 7	Sporadic
Que.	Nord-est	Sporadic
Que.	Québec et Chaudieres-Appalaches	Localized
Que.	Centre-du-Québec	Sporadic
Que.	Montréal et Laval	Sporadic
Que.	Ouest-du-Québec	Sporadic
Que.	Montérégie	Sporadic
Ont.	Central East	Sporadic
Ont.	Central West	Sporadic
Ont.	Eastern	Localized
Ont.	North East	Sporadic
Ont.	North West	No Activity
Ont.	South West	Sporadic
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	Localized
Sask.	South	Sporadic
Alta.	North Zone	Sporadic
Alta.	Edmonton	Sporadic
Alta.	Central Zone	Localized
Alta.	Calgary	Sporadic
Alta.	South Zone	Sporadic
B.C.	Interior	Localized
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	Sporadic
N.W.T.	South	Sporadic
Nvt.	Qikiqtaaluk	No Activity
Nvt.	Kivalliq	No Activity
Nvt.	Kitimeot	Sporadic

Laboratory Confirmed Influenza Detections

In week 49, the following results were reported from sentinel laboratories across Canada (Figure 2):

• The percentage of tests positive for influenza continued to 19.3%.
• 1,500 laboratory detections of influenza were reported, of which 99% were influenza A.

To date this season 6,158 laboratory-confirmed influenza detections have been reported (Figure 3):

• 99% have been influenza A.
• Among the 3,209 influenza A viruses subtyped, 94% have been A(H1N1)pdm09.
• Provincial and territorial differences in influenza type/subtype distribution are observed.

To date this season, detailed information on age and type/subtype has been received for 6,024 laboratory-confirmed influenza cases (Table 1):

• 70% of all influenza A(H1N1)pdm09 detections have been reported in individuals younger than 45 years of age.
• 68% 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	834	35	731	14

Figure 3 - Text description

Reporting provincesTable Figure 3 - Footnote 1	Week (December 2, 2018 to December 8, 2018)					Cumulative (August 26, 2018 to December 8, 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	153	90	15	48	2	358	217	58	83	5	363
AB	510	337	3	170	1	3136	1950	46	1140	19	3155
SK	175	109	3	63	0	866	484	14	368	0	866
MB	76	28	0	48	2	256	120	3	133	2	258
ON	94	52	11	31	1	315	150	72	93	28	343
QC	388	0	0	388	7	966	0	0	966	25	991
NB	43	7	0	36	1	68	10	0	58	1	69
NS	3	0	0	3	0	13	0	0	13	0	13
PEI	2	2	0	0	0	6	6	0	0	0	6
NL	4	0	0	4	0	14	1	0	13	1	15
YT	1	0	0	1	0	1	0	0	1	0	1
N.W.T	37	37	0	0	0	72	72	0	0	0	72
NU	0	0	0	0	0	6	6	0	0	0	6
Canada	1486	662	32	792	14	6077	3016	193	2868	81	6158
PercentageTable Figure 3 - Footnote 2	99%	45%	2%	53%	1%	99%	50%	3%	47%	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 UnS 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 2018-49

Age groups (years)	Cumulative (August 26, 2018 to December 8, 2018)
	Influenza A				B	Influenza A and B
	A Total	A(H1) pdm09	A(H3)	A (UnS)Footnote 1	Total	#	%
0-4	1277	698	4	575	10	1287	21%
5-19	1247	637	5	605	15	1262	21%
20-44	1490	724	27	739	13	1503	25%
45-64	1131	555	43	533	9	1140	19%
65+	813	331	167	315	19	832	14%
Total	5958	2945	246	2767	66	6024	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 49, 2.1% 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	1.6%	1.8%	1.0%	2.8%
49	2.1%	1.5%	1.1%	1.8%

Participatory Syndromic Surveillance

In week 49, 2,218 participants reported to FluWatchers, of which 44 (2.0%) reported symptoms of cough and fever (Figure 5).

Among the 53 participants who reported fever and cough:

• 27% consulted a healthcare professional;
• 80% reported days missed from work or school, resulting in a combined total of 118 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%

Influenza Outbreak Surveillance

In week 49, five new laboratory-confirmed influenza outbreaks were reported in long-term care (2), acute care facilities (1) and other settings (2). Four new ILI outbreaks were also reported in week 49.

To date this season, 52 laboratory-confirmed influenza outbreaks have been reported (Figure 6):

• 25 outbreaks were in LTCF, 11 were in schools, seven in acute care facilities, and eight were in other settings.
• All of the 36 outbreaks for which the influenza type was available were associated with influenza A.
• Among the 33 outbreaks for which the influenza A subtype was available:
  • 25 were associated with influenza A(H1N1)pdm09;
  • 8 were associated with A(H3N2),

To date this season, 35 ILI outbreaks have been reported; 26 occurred in LTCF, six 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	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	3	0
47	2	3	0	0	0
48	2	6	1	2	0
49	1	2	2	0	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 705 influenza-associated hospitalizations have been reported by participating provinces and territories^{Footnote 1}.

Hospitalizations (Table 2):

• 99% (702) 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 90 ICU admissions and 16 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 2018-49

Age Groups	Cumulative (August 26, 2018 to December 8, 2018)
	Influenza A	Influenza B	Rate per 100,000 population
0-4	131	0	27.5223961
5-19	88	0	6.3418807
20-44	115	0	4.0420613
45-64	182	0	8.3629752
65+	186	3	15.5342679
Total	702	3
%	100%	0%

Pediatric Influenza Hospitalizations and Deaths

In week 49, 37 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 (Figure 7).

To date this season, 228 pediatric hospitalizations have been reported (Figure 8):

• All but three cases have been associated with influenza A.
• Among the 154 cases for which the influenza subtype was available, 152 (98.7%) were associated with A(H1N1)pdm09.

To date this season, 33 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
48	46	9	2	23
49	37	15	3	28

Figure 8 - Text description

Age Group	Total
0-5 mo	20
6-23 mo	62
2-4 yr	65
5-9 yr	61
10-16 yr	20

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, 38 hospitalizations have been reported:

• 33 (87%) were associated with influenza A and 5 with influenza B.
• 20 of the 38 cases (53%) were adults 65 years of age and older.

Influenza Strain Characterizations

Since September 1, 2018, the National Microbiology Laboratory (NML) has characterized 182 influenza viruses (25 A(H3N2), 144 A(H1N1) and 13 B) that were received from Canadian laboratories. 

Genetic Characterization of Influenza A (H3N2):

23 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:

• Three viruses belonged to genetic group 3C.2a.
• 20 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):

• Two 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 two influenza A (H3N2) viruses characterized belonged to genetic group 3C.2a1.

Influenza A(H1N1):

• 144 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).

• 13 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:

132 influenza A (20 A(H3N2) and 112 A(H1N1)) viruses were tested for resistance to amantadine and it was found that:

• All 132 influenza A viruses were resistant to amantadine.

Antiviral Resistance – Oseltamivir:

185 influenza viruses (22 A(H3N2), 150 A(H1N1) and 13 B) were tested for resistance to oseltamivir and it was found that:

• All 185 influenza viruses were sensitive to oseltamivir

Antiviral Resistance – Zanamivir:

138 influenza viruses (22 A(H3N2), 150 H1N1 and 13 B) were tested for resistance to zanamivir and it was found that:

• All 138 influenza viruses were sensitive to zanamivir.