FluWatch report: January 26 to February 1, 2020 (week 05)

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

During week 05, influenza activity was reported in all provinces and territories and in almost all regions (51). Among these regions, 56% reported sporadic activity, 38% reported localized activity, and 4% reported widespread activity (Figure 1).

Figure 1 - Text equivalent

Province	Influenza Surveillance Region	Activity Level
N.L.	Eastern	Widespread
N.L.	Labrador-Grenfell	Sporadic
N.L.	Central	Sporadic
N.L.	Western	No Data
P.E.I.	Prince Edward Island	Sporadic
N.S.	Zone 1 - Western	Sporadic
N.S.	Zone 2 - Northern	Sporadic
N.S.	Zone 3 - Eastern	Sporadic
N.S.	Zone 4 - Central	Sporadic
N.B.	Region 1	Localized
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	Sporadic
Que.	Centre-du-Québec	Localized
Que.	Montréal et Laval	Sporadic
Que.	Ouest-du-Québec	Sporadic
Que.	Montérégie	Sporadic
Ont.	Central East	Localized
Ont.	Central West	Localized
Ont.	Eastern	Localized
Ont.	North East	Localized
Ont.	North West	Localized
Ont.	South West	Localized
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	Localized
Alta.	North Zone	Sporadic
Alta.	Edmonton	Localized
Alta.	Central Zone	Sporadic
Alta.	Calgary	Localized
Alta.	South Zone	Sporadic
B.C.	Interior	Sporadic
B.C.	Fraser	Widespread
B.C.	Vancouver Coastal	Sporadic
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	Localized
Nvt.	Kitimeot	No Activity

Laboratory-Confirmed Influenza Detections

In week 05, the percentage of laboratory tests positive for influenza continued to increase and surpassed the previous peak reported in late December. The percentage of tests positive for influenza was 30% in week 05, up from 28% in week 04. Influenza A and B continue to co-circulate; however, the recent increase in laboratory detections is mainly driven by an increase in influenza B detections.

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

• The percentage of tests positive for influenza B was 14% week 05. This continues to be three times greater than the average (4.2%) for this time of year.
• The percentage of tests positive for influenza A was 16% in week 05, which is average for this time of year.
• Among subtyped influenza A detections, influenza A(H1N1) accounted for 84% of detections, up from 75% in week 04.

To date this season (weeks 35 to 05), 29,023 laboratory detections of influenza were reported:

• 58% (16,763) were influenza A.
• Among subtyped influenza A detections (4,470), A(H1N1) is the predominant subtype this season (61%).

Detailed information on age and type/subtype has been received for 20,036 laboratory-confirmed influenza cases (Table 1). To date this season (weeks 35 to 05):

• Among cases of influenza A(H3N2) (1,524), the largest proportion were in adults 65 years of age and older (47%).
• Cases of influenza B (8,993) were primarily in younger age groups; 55% of cases were under 20 years of age and 32% between 20 and 44 years of age.
• Among cases of influenza A(H1N1) (1,934), 31% 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	1794	78	403	2147	15.9	14.1

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 1, 2020)
	A Total	A(H1N1)	A(H3N2)	A(UnS)Table Figure 3 - Footnote 3	B Total	A & B Total
B.C.	1378	174	234	380	1014	2392
Alta.	2423	635	1045	743	2536	4959
Sask.	618	0	0	618	179	797
Man.	569	78	68	423	638	1207
Ont.	4559	1778	321	2460	1200	5759
Que.	6704	0	0	6704	6123	12827
N.B.	273	27	20	226	383	656
N.S.	51	2	1	48	55	106
P.E.I.	30	0	0	30	26	56
N.L.	61	4	24	33	71	132
Y.T.	31	4	8	19	6	37
N.W.T	47	38	8	1	25	72
Nvt.	19	1	0	18	4	23
Canada	16763	2741	1729	11703	12260	29023
PercentageTable Figure 3 - Footnote 2	58%	16%	10%	70%	42%	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 2020-01 to 2020-05

Age groups (years)	Cumulative (August 25, 2019 to February 1, 2020)
	Influenza A				B	Influenza A and B
	A Total	A(H1N1)	A(H3N2)	A (Un subtyped)Table 1 Footnote 1	Total	#	%
0-4	1659	227	149	1283	1915	3574	18%
5-19	1094	126	192	776	3051	4145	21%
20-44	2254	500	237	1517	2876	5130	26%
45-64	2077	477	235	1365	506	2583	13%
65+	3959	604	711	2644	645	4604	23%
Total	11043	1934	1524	7585	8993	20036	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 05, 1.6% 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 05: 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	1.2%	1.9%	1.4%	2.7%
52	2.6%	2.0%	1.0%	3.1%
1	2.9%	3.4%	1.9%	5.4%
2	1.6%	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%

FluWatchers

The proportion of FluWatchers participants reporting symptoms of cough and fever increased in week 05 compared to the previous week. In week 05, 3,165 participants reported to FluWatchers, of which 3.4% (109) reported symptoms of cough and fever (Figure 5).

Among the 109 participants who reported cough and fever:

• 20% consulted a healthcare professional;
• 74% reported days missed from work or school, resulting in a combined total of 250 missed days of work or school.

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

Number of Participants Reporting in Week 05: 3,165

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%

Online Figure – Geographic distribution of FluWatchers participants reporting cough and fever, Canada, week 2020-05

Click on the map to access the link

Influenza Outbreak Surveillance

In week 05, a total of 28 outbreaks were reported: 14 in long term care facilities, 5 in acute care facilities, 5 in facilities categorized as ‘other’, which includes facilities such as private personal care homes, correctional facilities, and colleges/universities and 4 in schools and daycares (Figure 6). In addition, 43 ILI outbreaks in schools/daycares were reported.

To date this season, a total of 576 laboratory-confirmed influenza outbreaks have been reported; 61% (352) in long-term care facilities, 25% (144) in facilities categorized as ‘other’, 11% (64) in acute care facilities, and 3% (16) in schools/daycares. Of the 544 outbreaks where influenza type was reported, 90% (487) were due to influenza A. Among the 233 outbreaks for which the influenza A subtype was reported, 55% (127) were associated with A(H3N2). To date this season, 79 ILI outbreaks in schools/daycares have also been reported.

Number of provinces and territories reporting in Week 05: 13 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	8	1	1	0
50	3	10	4	1	0
51	4	14	11	0	0
52	4	35	15	0	0
1	16	59	38	0	0
2	11	79	35	0	0
3	9	44	5	1	0
4	5	46	18	6	0
5	5	14	5	4	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 1,358 influenza-associated hospitalizations were reported by participating provinces and territories1.

• 65% of the cases were associated with influenza A.
• Of the 661 cases for which subtype was reported, 67% were associated with influenza A(H3N2).
• The highest cumulative hospitalization rates up to week 05 were among children under 5 years of age and adults 65 years of age and older (44/100,000 population).

129 ICU admissions and 38 deaths have been reported.

• 58% of the ICU admissions and 76% of the deaths were associated with influenza A.

Number of provinces and territories reporting in Week 05: 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	1.9	7.5
50	11.1	3.0	1.8	2.2	10.0
51	14.3	3.7	2.5	3.4	13.3
52	18.5	5.6	3.7	4.5	18.9
1	27.3	6.2	4.5	6.3	27.0
2	31.3	7.3	5.2	7.6	31.5
3	38.0	8.2	6.8	9.4	38.7
4	41.6	8.9	7.5	10.4	42.0
5	44.4	9.6	8.2	10.8	43.5

Pediatric Influenza Hospitalizations and Deaths

In week 05, 117 pediatric (≤16 years of age) laboratory-confirmed influenza-associated hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network (Figure 8). The weekly number of cases increased compared to the previous week. 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 this season. The number of influenza A-associated pediatric hospitalizations is above the average for this time of year. The number of hospitalizations with influenza B is well above average compared to previous seasons, and occurring earlier in the season.
To date this season (weeks 35 to 05):

• 774 pediatric hospitalizations have been reported by the IMPACT network, of which 50% (389) were associated with influenza B and 50% (385) with influenza A.
• The largest proportion of hospitalizations (65%) were among children under 5 years of age (Figure 9).
• Among cases in children under 5 years of age (503), 56% were associated with influenza A, compared to cases in children 5 to 16 years of age (271), among whom 60% of cases were associated with influenza B.
• 114 ICU admissions were reported, of which 50% (46) 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	97	54	14	89
1	110	55	21	94
2	99	40	12	63
3	83	44	28	64
4	91	53	34	93
5	117	47	25	70

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 2019-20 season. In week 05, the number of cases increased slightly, interrupting a recent declining trend.

To date this season, 474 hospitalizations, 33 intensive care unit admissions, and 14 deaths have been reported (Figure 10).

• The majority of hospitalizations have been due to influenza A (85%), and among those subtyped (112) 92% were influenza A(H1N1).
• Among cases with influenza A, the largest proportion of hospitalizations were in adults 65-79 years of age (32%) and adults 80 years of age and older (30%). Among the 72 cases with influenza B, 38% were between 16 and 34 years of age and 39% were 65 years of age and older (Figure 11).
• 73% of hospitalized cases reported at least one type of comorbid condition.

Influenza Strain Characterizations

From September 1, 2019 to February 6, 2020, the National Microbiology Laboratory (NML) has characterized 555 influenza viruses (235 A(H1N1), 145 A(H3N2) and 175 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 41 influenza A(H3N2) viruses antigenically characterized to date, the majority (85%) showed reduced titer by HI assay to A Kansas/14/2017 using antiserum raised against egg-propagated A Kansas/14/2017. Six 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 235 A(H1N1) viruses characterized to date, 62% 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 175 influenza B viruses antigenically characterized this season, the vast majority (173) belonged to the B/Victoria lineage. Two viruses were antigenically characterized as similar to B/Phuket/3073/2013 (B/Yamagata lineage).

The majority (91%, 157) 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 12 c).

Sequence analysis of 105 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 6, 2020, the following results were reported:

Oseltamivir:

371 influenza viruses (132 A(H3N2), 117 A(H1N1) and 122 B) were tested for resistance to oseltamivir:

• All influenza A(H3N2) and B viruses were sensitive to oseltamivir.
• Among the A(H1N1) viruses tested, 116 (99%) were sensitive to oseltamivir and one virus was resistant to oseltamivir with the H275Y mutation in the neuraminidase gene.

Zanamivir:

371 influenza viruses (132 A(H3N2), 117 A(H1N1) and 122 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 Coverage

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

Vaccine Effectiveness

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