FluWatch report: December 16, 2018 to December 29, 2018 (Week 51-52)

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	Sporadic
N.S.	Zone 2 - Northern	No Activity
N.S.	Zone 3 - Eastern	Sporadic
N.S.	Zone 4 - Central	Sporadic
N.B.	Region 1	Sporadic
N.B.	Region 2	Sporadic
N.B.	Region 3	Sporadic
N.B.	Region 4	Sporadic
N.B.	Region 5	Sporadic
N.B.	Region 6	Sporadic
N.B.	Region 7	Localized
Que.	Nord-est	No Data
Que.	Québec et Chaudieres-Appalaches	No Data
Que.	Centre-du-Québec	No Data
Que.	Montréal et Laval	No Data
Que.	Ouest-du-Québec	No Data
Que.	Montérégie	No Data
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	No Data
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	Localized
B.C.	Vancouver Coastal	Sporadic
B.C.	Vancouver Island	Sporadic
B.C.	Northern	Sporadic
Y.T.	Yukon	Sporadic
N.W.T.	North	No Data
N.W.T.	South	No Data
Nvt.	Qikiqtaaluk	No Data
Nvt.	Kivalliq	No Data
Nvt.	Kitimeot	No Data

Laboratory Confirmed Influenza Detections

In weeks 51 and 52, the following results were reported from sentinel laboratories across Canada (Figure 2):

• The percentage of tests positive for influenza continued to increase from 25.1% in week 51 to  29.4% in week 52.
• A total 3,387 laboratory detections of influenza were reported, of which 99% were influenza A.

To date this season 13,796 laboratory-confirmed influenza detections have been reported (Figure 3):

• 99% have been influenza A.
• Among the 6,007 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 11,531 laboratory-confirmed influenza cases (Table 1):

• 68% of all influenza A(H1N1)pdm09 detections have been reported in individuals younger than 45 years of age.
• 63% 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	1833	34	681	21
52	1554	40	733	13

Figure 3 - Text description

Reporting provincesTable Figure 3 - Footnote 1	Week (December 16, 2018 to December 29, 2018)					Cumulative (August 26, 2018 to December 29, 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	785	486	5	294	1	1472	816	67	589	9	1481
AB	737	576	15	146	6	4519	2954	68	1497	26	4545
SK	27	0	2	25	0	1723	1060	51	612	0	1723
MB	239	43	0	196	0	622	176	3	443	2	624
ON	572	241	52	279	7	1023	459	141	423	40	1063
QC	1,919	0	0	1,919	20	3475	0	0	3475	51	3526
NB	391	25	1	365	0	547	42	1	504	2	549
NS	14	0	0	14	0	32	0	0	32	0	32
PEI	14	14	0	0	0	21	21	0	0	0	21
NL	49	0	0	49	0	80	1	0	79	1	81
YT	5	3	0	2	0	9	5	0	4	0	9
N.W.T	23	22	1	0	0	135	133	2	0	0	135
NU	1	1	0	0	0	7	7	0	0	0	7
Canada	4776	1411	76	3289	34	13665	5674	333	7658	131	13796
PercentageTable Figure 3 - Footnote 2	99%	30%	2%	69%	1%	99%	42%	2%	56%	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 2018-52

Age groups (years)	Cumulative (August 26, 2018 to December 29, 2018)
	Influenza A				B	Influenza A and B
	A Total	A(H1) pdm09	A(H3)	A (UnS)Footnote 1	Total	#	%
0-4	2512	1058	12	1442	18	2530	22%
5-19	2149	968	9	1172	23	2172	19%
20-44	2634	1118	46	1470	16	2650	23%
45-64	2302	935	60	1307	18	2320	20%
65+	1830	568	214	1048	29	1859	16%
Total	11427	4647	341	6439	104	11531	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 50, 1.6% of visits to healthcare professionals were due to influenza-like illness (ILI) (Figure 4). In weeks 51 and 52, an insufficient number of sentinels reported ILI activity. Data will be updated in the report for week 01.

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	1.8%	1.5%	1.1%	1.8%
50	1.6%	2.1%	1.4%	2.7%
51	N/A	2.3%	1.6%	3.2%
52	N/A	3.6%	1.9%	5.0%

Participatory Syndromic Surveillance

In week 52, 1,947 participants reported to FluWatchers, of which 70 (4%) reported symptoms of cough and fever (Figure 5).

Among the 70 participants who reported fever and cough:

• 27% consulted a healthcare professional;
• 63% reported days missed from work or school, resulting in a combined total of 150 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%

Influenza Outbreak Surveillance

In weeks 51 and 52, 15 new laboratory-confirmed influenza outbreaks were reported: long-term care facilities (LTCF) (4), acute care facilities (6), schools (1), and other settings (4).

To date this season, 86 laboratory-confirmed influenza outbreaks have been reported (Figure 6): 

• 37 outbreaks were in LTCF, 17 were in schools, 14 in acute care facilities, and 18 were in other settings.
• All of the 73 outbreaks for which the influenza type was available were associated with influenza A.
• Among the 50 outbreaks for which the influenza A subtype was available:
  • 82% (41) were associated with influenza A(H1N1)pdm09;
  • 18% (9) were associated with A(H3N2),

To date this season, 38 ILI outbreaks have been reported; 28 occurred in LTCF, seven 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	4	0
49	1	3	3	1	0
50	3	5	5	2	0
51	2	2	1	1	0
52	2	4	3	0	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 1046 influenza-associated hospitalizations have been reported by participating provinces and territories^{Footnote 1}.

Hospitalizations (Table 2):

• 99.6% (1042) 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 119 ICU admissions and 24 deaths have been reported.
  • 44% (52) of reported ICU admissions were in adults aged 45-64 years.
  • All reported deaths were associated with influenza A.

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 2018-52

Age Groups	Cumulative (August 26, 2018 to December 29, 2018)
	Influenza A	Influenza B	Rate per 100,000 population
0-4	179	1	37.82
5-19	124	0	8.94
20-44	164	0	5.76
45-64	272	0	12.50
65+	303	3	25.15
Total	1042	4
%	99.6	0.4

Pediatric Influenza Hospitalizations and Deaths

In weeks 51 and 52, 133 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, 414 pediatric hospitalizations have been reported (Figure 8):

• 99% (408) of cases have been associated with influenza A.
• Among the 203 cases for which the influenza subtype was available, 199 (98%) were associated with A(H1N1)pdm09.

To date this season, 71 ICU admissions, and less than five deaths have been reported.

• 85% (60) of ICU admissions were in children under the age of 10
• 99% (69) of ICU admissions have been associated with influenza A.

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	39	15	3	28
50	49	23	4	47
51	68	32	4	72
52	66	47	7	92

Figure 8 - Text description

Age Group	Total
0-5 mo	37
6-23 mo	105
2-4 yr	139
5-9 yr	98
10-16 yr	35

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 1st for the 2018-19 season.

To date this season, 115 hospitalizations have been reported (Figure 9):

• 108 (94%) were associated with influenza A.
• 58 cases (50%) were adults 65 years of age and older.
• The most commonly reported comorbidity among hospitalized cases was endocrine disorders, which were reported in 84% of hospitalized cases.

Figure 9 - Text description

Age Group	Total
20-34 yr	16
35-49 yr	17
50-64 yr	24
65-79 yr	35
80+ yr	23

Influenza Strain Characterizations

Since September 1, 2018, the National Microbiology Laboratory (NML) has characterized 395 influenza viruses (30 A(H3N2), 350 A(H1N1) and 15 B) that were received from Canadian laboratories.

Genetic Characterization of Influenza A (H3N2):

24 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.
• 21 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):

• Six 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.
• Four influenza A (H3N2) viruses characterized belonged to genetic group 3C.2a1. Sequencing is pending for the remaining three viruses.

Influenza A(H1N1):

• 345 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.
• Five 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).

• One influenza B virus was characterized as B/Colorado/06/2017, which belongs to the Victoria lineage and is 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:

274 influenza A (35 A(H3N2) and 239 A(H1N1)) viruses were tested for resistance to amantadine and it was found that:

• All 274 influenza A viruses were resistant to amantadine.

Antiviral Resistance – Oseltamivir:

263 influenza viruses (28 A(H3N2), 221 A(H1N1) and 14 B) were tested for resistance to oseltamivir and it was found that:

• All 263 influenza viruses were sensitive to oseltamivir

Antiviral Resistance – Zanamivir:

263 influenza viruses (28 A(H3N2), 221 H1N1 and 14 B) were tested for resistance to zanamivir and it was found that:

• All 263 influenza viruses were sensitive to zanamivir.