FluWatch report: February 9 to 15, 2020 (week 07)

Influenza/Influenza-like Illness (ILI) Activity (geographic spread)

During week 07, influenza activity was reported in almost all regions (44 out of 45) in reporting provinces and territories. Among these regions, 40% reported sporadic activity, 56% reported localized activity, and 2% reported widespread activity (Figure 1).

Figure 1 - Text equivalent

Province	Influenza Surveillance Region	Activity Level
N.L.	Eastern	Sporadic
N.L.	Labrador-Grenfell	Sporadic
N.L.	Central	Localized
N.L.	Western	Sporadic
P.E.I.	Prince Edward Island	Localized
N.S.	Zone 1 - Western	Localized
N.S.	Zone 2 - Northern	Localized
N.S.	Zone 3 - Eastern	No Activity
N.S.	Zone 4 - Central	Localized
N.B.	Region 1	Sporadic
N.B.	Region 2	Localized
N.B.	Region 3	Localized
N.B.	Region 4	Localized
N.B.	Region 5	Sporadic
N.B.	Region 6	Localized
N.B.	Region 7	Localized
Que.	Nord-est	Sporadic
Que.	Québec et Chaudieres-Appalaches	Localized
Que.	Centre-du-Québec	Widespread
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	No Data
Man.	Prairie Mountain	No Data
Man.	Interlake-Eastern	No Data
Man.	Winnipeg	No Data
Man.	Southern Health	No Data
Sask.	North	No Data
Sask.	Central	No Data
Sask.	South	No Data
Alta.	North Zone	Sporadic
Alta.	Edmonton	Localized
Alta.	Central Zone	Sporadic
Alta.	Calgary	Localized
Alta.	South Zone	Localized
B.C.	Interior	Sporadic
B.C.	Fraser	Localized
B.C.	Vancouver Coastal	Localized
B.C.	Vancouver Island	Localized
B.C.	Northern	Sporadic
Y.T.	Yukon	Sporadic
N.W.T.	North	Sporadic
N.W.T.	South	Sporadic
Nvt.	Qikiqtaaluk	Sporadic
Nvt.	Kivalliq	Sporadic
Nvt.	Kitimeot	Sporadic

Laboratory-Confirmed Influenza Detections

In week 07, the percentage of laboratory tests positive for influenza was similar to the previous two weeks at 29% and remains similar to the peak percentages reported since late December. Influenza A and B continue to co-circulate.

The following results were reported from sentinel laboratories across Canada (Figures 2 and 3):

• The percentage of tests positive for influenza B was 13% in week 07. This continues to be more than two times the average (5.3%) for this time of year.
• The percentage of tests positive for influenza A was 16% in week 07, which is similar to the previous six weeks, and below average for this time of year.
• Among subtyped influenza A detections, influenza A(H1N1) accounted for 83% of detections, a similar proportion to the previous two weeks.

To date this season (weeks 35 to 07), 38,671 laboratory detections of influenza were reported

• 57% (22,035) were influenza A.
• Among subtyped influenza A detections (5,279), A(H1N1) is the predominant subtype this season (64%).

Detailed information on age and type/subtype has been received for 30,142 laboratory-confirmed influenza cases (Table 1). To date this season (weeks 35 to 07):

• Among cases of influenza A(H3N2) (1,662), the largest proportion was in adults 65 years of age and older (46%).
• Cases of influenza B (13,795) were primarily in younger age groups; 57% of cases were under 19 years of age and 30% between 20 and 44 years of age.
• Among cases of influenza A(H1N1) (2,414), 30% of cases were in adults 65 years of age and older, with approximately equal proportions in adults 20-44 years and 45-64 years (~25%).

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(H3N2)	A(H1N1)pdm09	Influenza B	Percent Positive A	Percent Positive B
35	10	16	0	2	1.3	0.1
36	11	13	2	2	1.1	0.1
37	5	17	2	5	0.9	0.2
38	11	15	3	6	1.0	0.2
39	11	21	2	3	1.0	0.1
40	34	9	1	2	1.2	0.1
41	34	18	0	5	1.4	0.1
42	54	12	1	14	1.6	0.3
43	44	13	7	17	1.6	0.3
44	43	23	16	17	1.8	0.3
45	57	57	20	39	2.2	0.7
46	82	43	23	77	2.7	1.4
47	118	49	33	124	3.1	1.9
48	225	67	42	223	4.9	3.2
49	281	79	41	336	5.3	4.1
50	463	100	73	654	7.7	8.0
51	794	149	169	1094	10.6	10.4
52	1223	267	197	1439	15.0	12.7
1	1620	261	431	1533	15.8	10.3
2	1690	165	493	1463	15.8	9.4
3	1587	131	414	1418	16.2	10.3
4	1736	126	368	1952	15.2	12.7
5	1987	96	437	2269	16.0	13.7
6	1982	70	337	2265	15.6	14.1
7	1741	61	293	1791	15.7	12.8

Footnote *

Specimens from NWT, YT, and Nvt are sent to reference laboratories in other provinces.

Return to footnote * referrer

Figure 3 - Text equivalent

ProvincesTable Figure 3 - Footnote 1	Cumulative (August 25, 2019 to February 15, 2020)
	A Total	A(H1N1)	A(H3N2)	A(UnS)Table Figure 3 - Footnote 3	B Total	A & B Total
B.C.	1864	200	235	609	1415	3279
Alta.	3022	880	1131	1011	2869	5891
Sask.	1196	0	0	1196	556	1752
Man.	944	119	90	735	783	1727
Ont.	5373	2106	356	2911	1627	7000
Que.	8880	0	0	8880	8356	17236
N.B.	432	36	22	374	717	1149
N.S.	68	2	1	65	96	164
P.E.I.	62	0	0	62	48	110
N.L.	63	4	24	35	103	166
Y.T.	36	4	8	24	8	44
N.W.T	58	49	8	1	46	104
Nvt.	37	2	2	33	12	49
Canada	22035	3402	1877	15936	16636	38671
PercentageTable Figure 3 - Footnote 2	57%	15%	9%	72%	43%	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 Table Figure 3 - Footnote 3 referrer

Table 1 - Cumulative numbers of positive influenza specimens by type, subtype and age group reported through case-based laboratory reporting, Canada, weeks 2019-35 to 2020-07

Age groups (years)	Cumulative (August 25, 2019 to February 15, 2020)
	Influenza A				B	Influenza A and B
	A Total	A(H1N1)	A(H3N2)	A (Un subtyped)Table 1 Footnote 1	Total	#	%
0-4	2645	287	162	2196	3118	5763	19%
5-19	1843	168	215	1460	4804	6647	22%
20-44	3451	624	263	2564	4157	7608	25%
45-64	3164	608	252	2304	764	3928	13%
65+	5244	727	770	3747	952	6196	21%
Total	16347	2414	1662	12271	13795	30142	100%
Table 1 Footnote 1 Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available. Table 1 Return to footnote 1 referrer

Syndromic / Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 07, 1.4% of visits to healthcare professionals were due to influenza-like illness (ILI) which is below the average for this time of year (Figure 4).

Number of Sentinels Reporting in Week 07: 90

The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2014-2015 to 2018-2019

Figure 4 - Text equivalent

Surveillance Week	2019-20	Average	Min	Max
35	0.6%	0.6%	0.4%	0.9%
36	0.4%	0.6%	0.4%	0.9%
37	0.7%	0.7%	0.5%	1.0%
38	1.1%	0.7%	0.6%	1.0%
39	0.8%	0.9%	0.5%	1.2%
40	1.0%	1.2%	0.8%	1.7%
41	0.9%	1.7%	0.8%	2.8%
42	1.1%	1.6%	1.2%	2.1%
43	0.7%	1.2%	0.8%	1.7%
44	0.9%	1.2%	0.7%	1.7%
45	0.7%	1.2%	0.9%	1.5%
46	1.1%	1.4%	1.2%	1.8%
47	1.2%	1.6%	1.1%	2.2%
48	0.9%	1.5%	1.1%	2.2%
49	1.0%	1.7%	1.0%	2.8%
50	1.4%	1.5%	1.1%	1.7%
51	1.1%	1.9%	1.4%	2.7%
52	2.5%	2.0%	1.0%	3.1%
1	2.9%	3.4%	1.9%	5.4%
2	1.5%	3.4%	1.8%	5.7%
3	1.8%	2.3%	1.3%	3.7%
4	1.5%	2.0%	1.1%	2.9%
5	1.6%	2.1%	1.4%	3.1%
6	1.8%	2.4%	1.4%	4.0%
7	1.4%	2.4%	0.9%	3.5%

FluWatchers

The proportion of FluWatchers participants reporting symptoms of cough and fever decreased in week 07 compared to the previous week. In week 07, 3,044 participants reported to FluWatchers, of which 2.6% (79) reported symptoms of cough and fever (Figure 5).

Among the 79 participants who reported cough and fever:

• 22% consulted a healthcare professional;
• 66% reported days missed from work or school, resulting in a combined total of 187 missed days of work or school.

If you are interested in becoming a FluWatcher, sign up today.

Number of Participants Reporting in Week 07: 3,044

Figure 5 - Text equivalent

Surveillance Week	% cough and fever
40	2.2%
41	1.8%
42	1.7%
43	2.2%
44	1.6%
45	1.4%
46	1.2%
47	1.5%
48	1.7%
49	2.2%
50	2.1%
51	2.6%
52	4.1%
1	4.3%
2	3.1%
3	3.3%
4	3.1%
5	3.4%
6	3.0%
7	2.6%

Online Figure – Geographic distribution of FluWatchers participants reporting cough and fever, Canada, week 2020-07

Click on the map to access the link

Influenza Outbreak Surveillance

In week 07, a total of 31 outbreaks were reported: 20 in long term care facilities, 10 in facilities categorized as ‘other', which includes facilities such as private personal care homes, correctional facilities, and colleges/universities, and one in a school/daycare (Figure 6). In addition, 7 ILI outbreaks in schools/daycares were reported.

To date this season, a total of 702 laboratory-confirmed influenza outbreaks have been reported; 61% (430) in long-term care facilities, 26% (185) in facilities categorized as ‘other’, 11% (74) in acute care facilities, and 2% (13) in schools/daycares. Of the 668 outbreaks where influenza type was reported, 88% (588) were due to influenza A. Among the 264 outbreaks for which the influenza A subtype was reported, 52% (136) were associated with A(H3N2). To date this season, 119 ILI outbreaks in schools/daycares have also been reported.

Number of provinces and territories reporting in week 07: 11 out of 13

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	1	0	0	0
39	0	1	0	0	0
40	0	2	0	0	0
41	0	2	1	0	0
42	1	0	0	0	0
43	0	0	1	0	0
44	0	0	1	0	0
45	0	2	4	0	0
46	1	4	0	0	0
47	0	2	1	1	0
48	1	6	2	2	0
49	2	10	1	1	0
50	4	10	4	1	0
51	4	16	11	0	0
52	4	48	15	0	0
1	18	82	40	0	0
2	12	91	35	0	0
3	10	49	7	1	0
4	5	48	19	2	0
5	5	23	9	0	0
6	7	13	24	4	0
7	0	20	10	1	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 1,687 influenza-associated hospitalizations were reported by participating provinces and territories1.

• 65% of the cases were associated with influenza A.
• Of the 786 cases for which subtype was reported, 61% were associated with influenza A(H3N2).
• The highest cumulative hospitalization rates up to week 07 were among children under 5 years of age and adults 65 years of age and older (54/100,000 population).

189 ICU admissions and 64 deaths have been reported.

• 65% of the ICU admissions and 72% of the deaths were associated with influenza A.

Number of provinces and territories reporting in week 07: 8 out of 9

Footnote ‡

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.

Return to footnote 1 referrer

Figure 7 - Text equivalent

Surveillance Week	0-4 yrs	5-19 yrs	20-44 yrs	45-64 yrs	65+ yrs
35	0.0	0.0	0.0	0.0	0.0
36	0.0	0.0	0.0	0.0	0.2
37	0.0	0.0	0.0	0.1	0.2
38	0.0	0.0	0.0	0.1	0.4
39	0.2	0.0	0.0	0.1	0.6
40	0.2	0.0	0.0	0.1	0.8
41	0.4	0.2	0.1	0.2	1.1
42	0.8	0.2	0.1	0.2	1.3
43	1.0	0.2	0.2	0.3	1.6
44	1.5	0.2	0.2	0.5	2.1
45	1.9	0.4	0.4	0.8	2.8
46	1.9	0.4	0.6	1.1	3.3
47	3.1	0.6	0.8	1.5	4.6
48	5.0	1.1	1.0	1.6	5.7
49	7.1	1.9	1.3	2.0	7.5
50	11.1	3.0	1.8	2.3	10.2
51	14.3	3.7	2.5	3.5	13.6
52	18.7	5.8	3.7	4.5	19.3
1	27.7	6.5	4.7	6.5	28.1
2	33.8	7.6	5.9	8.4	34.3
3	38.6	8.4	6.9	10.0	40.2
4	43.2	9.6	8.1	11.7	44.9
5	48.9	10.6	9.1	13.0	49.1
6	52.3	11.5	9.7	13.7	52.2
7	53.7	12.1	10.0	14.3	53.7

Pediatric Influenza Hospitalizations and Deaths

In week 07, 69 pediatric (≤16 years of age) laboratory-confirmed influenza-associated hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network (Figure 8). The number of cases due to influenza B remains high; however, in recent weeks, a growing proportion of cases have been due to influenza A.

The elevated number of cases this season compared to previous seasons is likely due to the concurrent circulation of influenza A and B. The number of influenza A-associated pediatric hospitalizations is above the average for this time of year which is expected when A(H1N1) is the predominant circulating virus. The number of hospitalizations with influenza B remains well above average compared to previous seasons.

To date this season (weeks 35 to 07):

• 951 pediatric hospitalizations have been reported by the IMPACT network, of which 51% (483) were associated with influenza A and 49% (468) with influenza B.
• The largest proportion of hospitalizations (65%) were among children under 5 years of age (Figure 9).
• 140 ICU admissions were reported, of which 52% were associated with influenza A.
• Less than five pediatric deaths have been reported.

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2014-15 to 2018-19

Figure 8 - Text equivalent

Surveillance week	2019-2020	Average	Min	Max
35	0	0	0	1
36	2	0	0	1
37	0	1	0	2
38	0	1	0	2
39	1	1	0	3
40	0	1	0	2
41	2	1	0	3
42	2	2	0	5
43	1	5	2	12
44	2	5	1	15
45	3	10	2	37
46	6	13	1	41
47	6	13	2	36
48	26	18	2	40
49	23	22	3	47
50	39	29	4	50
51	60	41	5	84
52	99	54	14	89
1	107	55	21	94
2	101	40	12	63
3	83	44	28	64
4	90	53	34	93
5	116	47	25	70
6	113	49	15	79
7	69	59	17	120

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 2019-20 season.

To date this season, 581 hospitalizations, 53 intensive care unit admissions, and 25 deaths have been reported (Figure 10).

• The majority of hospitalizations have been due to influenza A (82%), and among those subtyped (162) 91% were influenza A(H1N1).
• Among the 476 cases with influenza A, the largest proportion of hospitalizations were in adults 65-79 years of age (35%) and adults 80 years of age and older (32%). Among the 103 cases with influenza B, 33% were between 16 and 34 years of age (Figure 11).
• 87% of hospitalized cases reported at least one type of comorbid condition.

Influenza Strain Characterizations

From September 1, 2019 to February 20, 2020, the National Microbiology Laboratory (NML) has characterized 692 influenza viruses (355 A(H1N1), 155 A(H3N2) and 182 influenza B) that were received from Canadian laboratories.

Influenza A(H3N2)

Over recent years, circulating strains of A(H3N2) have evolved, and are increasingly difficult to characterize by hemagglutination inhibition (HI) assay. Genetic characterization is established by sequencing the hemagglutinin (HA) gene of the influenza viruses to compare their genetic properties.

Antigenic Characterization:

Among the 51 influenza A(H3N2) viruses antigenically characterized to date, the majority (80%) showed reduced titer by HI assay to A Kansas/14/2017 using antiserum raised against egg-propagated A Kansas/14/2017. Ten viruses were characterized as A Kansas/14/2017-like (Figure 12 a).

Genetic Characterization:

Nearly all (98%) of the 135 A(H3N2) viruses genetically characterized this season belonged to genetic group 3C.2a1b based on sequence analysis of the HA gene. Three viruses belonged to the genetic group 3C.3a (Figure 13).

Group 3C.2a1b viruses analysed represent:

• 90% (28 out of 31) viruses that were also antigenically characterized.
• 100% (104 out of 104) viruses which did not grow to sufficient hemagglutination titer for antigenic characterization by HI assay.

A/Kansas/14/2017 belongs to genetic group 3C.3a and is the influenza A(H3N2) component of the 2019-20 Northern Hemisphere influenza vaccine.

Influenza A(H1N1)

Among the 355 A(H1N1) viruses characterized to date, 57% were antigenically similar to A/Brisbane/02/2018 by HI testing using antiserum raised against egg-propagated A/Brisbane/02/2018 (Figure 12 b).

A/Brisbane/02/2018 is the influenza A(H1N1)component of the 2019-20 Northern Hemisphere influenza vaccine.

Influenza B

Among the 182 influenza B viruses antigenically characterized this season, the vast majority (180) belonged to the B/Victoria lineage. Two viruses were antigenically characterized as similar to B/Phuket/3073/2013 (B/Yamagata lineage).

The majority (89%, 161) of B/Victoria lineage viruses showed reduced titer by HI assay to B/Colorado/06/2017 using antiserum raised against cell culture-propagated B/Colorado/06/2017 (Figure 12c).

Sequence analysis of 150 B/Victoria lineage viruses with reduced titre to B/Colorado/06/2017 showed that 100% had a three amino acid deletion (162-164) in the HA gene. Sequencing is pending for the remaining viruses.

The recommended influenza B components for the 2019-20 Northern Hemisphere influenza vaccine are B/Colorado/06/2017 (Victoria lineage) and B/Phuket/3073/2013 (Yamagata lineage). B/Phuket/3073/2013 is included in the quadrivalent influenza vaccine.

Antiviral Resistance

The National Microbiology Laboratory (NML) also tests influenza viruses received from Canadian laboratories for antiviral resistance. From September 1, 2019 to February 20, 2020, the following results were reported:

Oseltamivir:

486 influenza viruses (140 A(H3N2), 164 A(H1N1) and 182 B) were tested for resistance to oseltamivir:

• All influenza A(H3N2) and B viruses were sensitive to oseltamivir.
• Among the A(H1N1) viruses tested, 163 (99%) were sensitive to oseltamivir and one virus was resistant to oseltamivir with the H275Y mutation in the neuraminidase gene.

Zanamivir:

486 influenza viruses (140 A(H3N2), 164 A(H1N1) and 182 B) were tested for resistance to zanamivir:

• All influenza viruses tested were sensitive to zanamivir.

Amantadine:

High levels of resistance to amantadine persist among influenza A(H1N1) and influenza A(H3N2) viruses. All viruses tested this season were resistant.

Vaccine Monitoring

Vaccine monitoring refers to activities related to the monitoring of influenza vaccine coverage and effectiveness.

Vaccine Effectiveness

The Canadian Sentinel Practitioner Surveillance Network (SPSN) provides estimates of the effectiveness of the seasonal influenza vaccine in preventing medically-attended illness due to laboratory-confirmed influenza among Canadians.

Based on data collected between November 1, 2019 and February 1, 2020, vaccine effectiveness (VE) was estimated to be 58% for any influenza, 44% for A(H1N1), 62% for A(H3N2), and 69% for influenza B. Substantial protection was observed among children 1 to 19 years of age against both influenza A and B. A good level of protection was also observed among working age adults (20-64 yrs) across all influenza types (Table 2). VE among adults 65 years and older, although imprecise due to small numbers, was lower at 18% (95% CI -59 to 58). The SPSN interim estimates are published and available online.

More information on the network and past VE findings can be viewed on the SPSN website.

Updated influenza vaccine effectiveness estimates will be published at the end of the 2019/2020 influenza season. At that time, sufficient data will likely be available to estimate VE by age-group, including adults 65 years and older with greater precision, as well as for influenza A subtypes.

Table 2 – Vaccine effectiveness estimates against medically-attended influenza illness, SPSN, November 1, 2019, to February 1, 2020

	All ages		1-19 years	20-64 years
	VE(%) (CI)Table 2 - Footnote *	N	VE(%) (CI)Table 2 - Footnote *	VE(%) (CI)Table 2 - Footnote *
All Influenza	58 (47, 66)	2808	74 (59, 84)	55 (41, 66)
Influenza A	49 (34, 60)	2128	70 (44, 84)	45 (25, 59)
Influenza A(H1N1)	44 (26, 58)	1948
Influenza A(H3N2)	62 (37, 77)	1561
Influenza B	69 (57, 77)	2080	77 (59, 87)	68 (51, 79)
CI: 95% confidence interval Footnote * adjusted for age group, province, specimen collection interval and calendar time Return to first table 2 footnote * referrer

Vaccine Coverage

Influenza vaccine coverage estimates for the 2019-20 season are anticipated to be available in February or March 2020.

Notes