FluWatch report: October 20 to 26, 2019 (week 43)

Influenza/Influenza-like Illness Activity (geographic spread)

During week 43, the number of regions reporting influenza activity increased compared to the previous week. The following influenza activity levels were reported (Figure 1):

• 26 regions (49%) reported sporadic activity, within 9 provinces and territories.

Figure 1 - Text equivalent

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

Laboratory-Confirmed Influenza Detections

In week 43, the number of detections of influenza was similar to the previous week. The following results were reported from sentinel laboratories across Canada (Figures 2 and 3):

• The percentage of tests positive for influenza remains at interseasonal levels, at 1.9%.
• A total of 96 laboratory detections of influenza were reported, of which 82% (79) were influenza A. The proportion of detections of influenza B increased in week 43.
• Among subtyped influenza A detections 12 out of 18 were influenza A(H3N2).

To date this season (weeks 35 to 43), 455 laboratory detections of influenza were reported:

• 88% (399) were influenza A.
• Among subtyped influenza A detections (150), 89% were influenza A(H3N2).

To date this season (weeks 35 to 43):

• 86% (292) were cases of influenza A.
• Among the 129 cases of influenza A for which the subtype was known, 88% of cases were A(H3N2).
• The majority of influenza A cases reported to date were in adults 65 years of age and older (49%). The majority of cases of influenza B were in younger age-groups; 80% of cases (37 of more than 43) were under 45 years of age.

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.

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	45	12	6	17	1.6	0.3

Figure 3 - Text equivalent

ProvincesTable Figure 3 - Footnote 1	Cumulative (August 25, 2019 to October 26, 2019)
	A Total	A(H1N1)	A(H3N2)	A(UnS)Table Figure 3 - Footnote 3	B Total	Total
B.C.	137	6	55	42	3	140
Alta.	79	8	49	22	17	96
Sask.	21	0	0	16	2	23
Man.	4	0	1	3	10	14
Ont.	35	2	18	15	12	47
Que.	105	0	0	105	10	115
N.B.	5	1	1	3	1	6
N.S.	1	0	0	1	1	2
P.E.I.	0	0	0	0	0	0
N.L.	1	0	1	0	0	1
Y.T.	10	0	8	2	0	10
N.W.T	1	0	0	1	0	1
Nvt.	0	0	0	0	0	0
Canada	399	17	133	210	56	455
PercentageTable Figure 3 - Footnote 2	88%	4%	33%	53%	12%	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 number of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reporting, Canada, weeks 2019-35 to 2019-43

Age groups (years)	Cumulative (August 25, 2019 to October 26, 2019)
	Influenza A				B	Influenza A and B
	A Total	A(H1N1)	A(H3N2)	A (Un subtyped)Table 1 Footnote 1	Total	#	%
0-4	>22	<5	8	14	11	37	11%
5-19	18	0	9	9	9	27	8%
20-44	>42	<5	14	28	17	60	18%
45-64	63	8	25	30	<5	>63	20%
65+	>140	<5	58	82	6	148	44%
Total	292	15	114	163	>43	>335	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 43, 0.9%, of visits to healthcare professionals were due to influenza-like illness (ILI) which is slightly below the average for this time of year (Figure 4).

Number of Sentinels Reporting in Week 43: 80

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	1.2%	0.7%	0.6%	1.0%
39	0.9%	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	0.9%	1.2%	0.8%	1.7%

FluWatchers

In week 43, 2,875 participants reported to FluWatchers, of which 2.2% (64) reported symptoms of cough and fever (Figure 5).

Among the 64 participants who reported cough and fever:

• 16% consulted a healthcare professional;
• 77% reported days missed from work or school, resulting in a combined total of 121 missed days of work or school.

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

Number of Participants Reporting in Week 43: 2,875

Figure 5 - Text equivalent

Surveillance Week	% cough and fever
40	2.2%
41	1.8%
42	1.7%
43	2.2%

Online Figure – Geographic distribution of FluWatchers participants reporting cough and fever, Canada, week 2019-43

Click on the map to access the link

Influenza Outbreak Surveillance

In week 43, one new outbreak was reported in a facility type categorized as ‘other’ (Figure 6).

To date this season, a total of 9 laboratory-confirmed influenza outbreaks have been reported; six in long-term care facilities, one in an acute care facility and two in a facility type categorized as ‘other’. All  but one of the reported outbreaks were due to influenza A. One ILI outbreak in a school /daycare has also been reported.

Number of provinces and territories reporting in week 43: 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

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 43, less than 5 influenza-associated hospitalizations were reported by participating provinces and territories^{Footnote 1}.

To date this season. 32 influenza-associated hospitalizations were reported by participating provinces and territories^{Footnote 1}.

• 78% of the cases were influenza A.
• Of the cases for which subtype was reported (25), 84% were associated with influenza A(H3N2).
• The majority of cases (53%) were ≥ 65 years of age.

Less than five ICU admissions and no deaths have been reported.

Number of provinces and territories reporting in week 43: 9 out of 9

Pediatric Influenza Hospitalizations and Deaths

In week 43, less than five pediatric (≤16 years of age) laboratory-confirmed influenza-associated hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network (Figure 7).

To date this season, 10 pediatric hospitalizations have been reported by the IMPACT network; four cases associated with influenza A and six with influenza B.

Figure 7 - 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	3	5	2	12

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 has not yet begun for the 2019-20 season.

Influenza Strain Characterizations

From September 1 to October 31, 2019, the National Microbiology Laboratory (NML) has characterized 19 influenza viruses (10 A(H3N2), 4 A(H1N1) and 5 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:

• Four influenza A(H3N2) viruses were antigenically characterized as A/Kansas/14/2017-like by HI assay using antiserum raised against cell culture-propagated A Kansas/14/2017.

Genetic Characterization:

All 10 A(H3N2) viruses this season have been genetically characterized, based on sequence analysis of the HA gene.

• Among the four A(H3N2) viruses antigenically characterized as A/Kansas/14/2017-like by HI testing.
  • All viruses belonged to genetic group 3C.2a1b.
• Among the six A(H3N2) viruses which did not grow to sufficient hemagglutination titer for antigenic characterization by HI assay:
  • All viruses belonged to genetic subclade 3C.2a1b.

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)

• Four A(H1N1) viruses characterized were antigenically similar to A/Brisbane/02/2018 by HI testing using antiserum raised against egg-propagated A/Brisbane/02/2018.

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

Influenza B

• One influenza B virus characterized was antigenically similar to B/Colorado/06/2017 by HI assay using antiserum raised against cell culture-propagated B/Colorado/06/2017.
• Four influenza B viruses showed reduced titer by HI assay. Sequence analysis showed that :
  • All of these viruses had a three amino acid deletion (162-164) in the HA gene.

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.

Oseltamivir:

Fourteen influenza viruses (9 H3N2, 2 H1N1 and 3 B) were tested for resistance to oseltamivir :

• All influenza viruses tested were sensitive to oseltamivir.

Zanamivir:

Fourteen influenza viruses (9 H3N2, 2 H1N1 and 3 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.

Provincial and International Surveillance Links

• British Columbia – Influenza Surveillance; Vaccine Effectiveness Monitoring
• Alberta – Influenza surveillance
• Saskatchewan – Influenza Reports
• Manitoba – Seasonal Influenza Reports
• Ontario – Ontario Respiratory Pathogen Bulletin
• Québec – Système de surveillance de la grippe (available in French only)
• New Brunswick – Influenza Surveillance Reports
• Prince Edward Island – Influenza Summary
• Nova Scotia – Respiratory Watch Report
• Newfoundland and Labrador – Surveillance and Disease Reports
• Yukon – Information on Pandemic, Influenza, Seasonal Flu, Avian Flu and H1N1
• Northwest Territories – Influenza/ Flu Information
• Nunavut – Influenza Information
• World Health Organization – FluNet (Global Influenza Surveillance Network)
• Pan American Health Organization – Influenza situation report
• U.S. Centers for Disease Prevention & Control (CDC) - Weekly Influenza Summary Update
• ECDC – Surveillance reports and disease data on seasonal influenza
• United Kingdom – Weekly Influenza Activity Reports
• Hong Kong Centre for Health Protection - Flu Express
• Australia – Influenza Surveillance Report and Activity Updates
• New Zealand – Influenza Weekly Update

Notes

The data in the FluWatch report represent surveillance data available at the time of writing. All data are preliminary and may change as more reports are received.

To learn more about the FluWatch program, see the Overview of influenza monitoring in Canada page.

For more information on the flu, see our Flu (influenza) web page.

We would like to thank all the Fluwatch surveillance partners participating in this year's influenza surveillance program.

This report is available on the Government of Canada Influenza webpage.

Ce rapport est disponible dans les deux langues officielles.