FluWatch report: October 27 to November 2, 2019 (week 44)

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Organization: Public Health Agency of Canada

Date published: 2019-11-08

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Overall Summary

  • Influenza activity remains at interseasonal levels at the national level.
  • The number of regions in Canada reporting influenza activity in week 44 was similar to the previous week.
  • Influenza A(H3N2) is the most common influenza virus circulating in Canada.
  • Weekly reporting of laboratory detections of respiratory viruses continues via our Respiratory Virus Detections Surveillance System.

Influenza/Influenza-like Illness Activity (geographic spread)

During week 44, 50% of regions (24) across 10 provinces and territories reported influenza activity, which is similar to the previous week. Among regions with influenza activity, all reported a sporadic level of activity (Figure 1).

Figure 1 – Map of influenza/ILI activity by province and territory, Canada, week 2019-44

Number of Regions Reporting in Week 44: 49 out of 53

Figure 1. Text equivalent follows.

Figure 1 - Text equivalent
Province Influenza Surveillance Region Activity Level
N.L. Eastern Sporadic
N.L. Labrador-Grenfell No Activity
N.L. Central Sporadic
N.L. Western Sporadic
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 Data
N.B. Region 2 No Activity
N.B. Region 3 Sporadic
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 Sporadic
Que. Montréal et Laval Sporadic
Que. Ouest-du-Québec Sporadic
Que. Montérégie No Activity
Ont. Central East Sporadic
Ont. Central West Sporadic
Ont. Eastern No Activity
Ont. North East No Activity
Ont. North West No Data
Ont. South West No Activity
Ont. Toronto Sporadic
Man. Northern Regional Sporadic
Man. Prairie Mountain Sporadic
Man. Interlake-Eastern No Activity
Man. Winnipeg Sporadic
Man. Southern Health No Activity
Sask. North Sporadic
Sask. Central Sporadic
Sask. South No Activity
Alta. North Zone No Activity
Alta. Edmonton Sporadic
Alta. Central Zone No Activity
Alta. Calgary Sporadic
Alta. South Zone Sporadic
B.C. Interior Sporadic
B.C. Fraser Sporadic
B.C. Vancouver Coastal Sporadic
B.C. Vancouver Island No Activity
B.C. Northern No Activity
Y.T. Yukon Sporadic
N.W.T. North No Activity
N.W.T. South Sporadic
Nvt. Qikiqtaaluk No Data
Nvt. Kivalliq No Data
Nvt. Kitimeot No Data

Laboratory-Confirmed Influenza Detections

In week 44, the number of detections of influenza continued to increase slowly. The following results were reported from sentinel laboratories across Canada (Figures 2 and 3):

To date this season (weeks 35 to 44), 563 laboratory detections of influenza were reported:

Detailed information on age and type/subtype has been received for more than 425 laboratory-confirmed influenza cases (Table 1). (The total number of cases is suppressed due to small values in Table 1).

To date this season (weeks 35 to 44):

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 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, week 2019-44

Number of Laboratories Reporting in Week 44: 32 out of 34

Figure 2. Text equivalent follows.

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 42 23 16 17 1.9 0.4

Figure 3 – Distribution of positive influenza specimens by type/subtype and province/territory1, Canada, weeks 2019-35 to 2019-44

Figure 3. Text equivalent follows.

Figure 3 - Text equivalent
ProvincesTable Figure 3 - Footnote 1 Cumulative (August 25, 2019 to November 2, 2019)
A Total A(H1N1) A(H3N2) A(UnS)Table Figure 3 - Footnote 3 B Total Total
B.C. 155 6 56 50 3 158
Alta. 108 18 64 26 24 132
Sask. 26 0 0 16 2 28
Man. 17 2 3 12 11 28
Ont. 40 4 22 14 16 56
Que. 119 0 0 119 15 134
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. 4 0 3 1 0 4
Y.T. 11 0 8 3 0 11
N.W.T 4 3 0 1 0 4
Nvt. 0 0 0 0 0 0
Canada 490 34 157 246 73 563
PercentageTable Figure 3 - Footnote 2 87% 7% 32% 50% 13% 100%
Table Figure 3 - Footnote 1

Specimens from NWT, YT, and Nvt are sent to reference laboratories in other provinces. However, data on laboratory-confirmed detections of influenza from Nunavut are not currently available.

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 2019-44
Age groups (years) Cumulative (August 25, 2019 to November 2, 2019)
Influenza A B Influenza A and B
A Total A(H1N1) A(H3N2) A (Un subtyped)Table 1 Footnote 1 Total # %
0-4 39 7 12 20 15 54 13%
5-19 >23 <5 10 13 14 38 9%
20-44 60 5 19 36 22 82 19%
45-64 74 14 27 33 <5 >74 18%
65+ >162 <5 70 92 7 173 41%
Total 363 31 138 194 >58 >425 100%
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 44, 1.0%, of visits to healthcare professionals were due to influenza-like illness (ILI) which is slightly below the average for this time of year (1.3%) (Figure 4).

Figure 4 – Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2019-35 to 2019-44

Number of Sentinels Reporting in Week 44: 78

Figure 4

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 0.8% 1.2% 0.8% 1.7%
44 1.0% 1.2% 0.7% 1.7%

FluWatchers

In week 44, 3,069 participants reported to FluWatchers, of which 1.6% (51) reported symptoms of cough and fever (Figure 5).

Among the 51 participants who reported cough and fever:

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

Figure 5 – Percentage of FluWatchers participants reporting cough and fever, Canada, week 2019-44

Number of Participants Reporting in Week 44: 3,069

Figure 5. Text equivalent follows.

Figure 5 - Text equivalent
Surveillance Week % cough and fever
40 2.2%
41 1.8%
42 1.7%
43 2.2%
44 1.7%

Online Figure – Geographic distribution of FluWatchers participants reporting cough and fever, Canada, week 2019-44

Click on the map to access the link

map

Influenza Outbreak Surveillance

In week 44, one new outbreak was reported in a facility type categorized as ‘other’, which includes facilities such as private personal care homes, correctional facilities, colleges/universities etc. (Figure 6).

To date this season, a total of 10 laboratory-confirmed influenza outbreaks have been reported; six in long-term care facilities, one in an acute care facility and three in a facility type categorized as ‘other’. Of the outbreaks where influenza type was reported, nine out of ten were due to influenza A. One ILI outbreak in a school/daycare has also been reported

Figure 6 – Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2019-35 to 2019-44

Number of provinces and territories reporting in week 44: 12 out of 13

Figure 6

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

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season. 45 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote 1.

Five ICU admissions and no deaths have been reported.

Number of provinces and territories reporting in week 44: 9 out of 9
Footnote 1

Influenza-associated hospitalizations are reported by N.L., P.E.I. N.S., N.B., Man., Alb., Y.T. and N.W.T. Only hospitalizations that require intensive medical care are reported by Sask. The cumulative rate of hospitalizations is calculated using the population by age-group in participating provinces and territories.

Footnote 1 referrer

Pediatric Influenza Hospitalizations and Deaths

In week 44, 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, 11 pediatric hospitalizations have been reported by the IMPACT network; seven cases associated with influenza A and four with influenza B.

Figure 7 – Number of pediatric (≤16 years of age) hospitalizations reported by the IMPACT network, by week, Canada, weeks 2018-35 to 2019-44

Figure 7

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

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
44 1 5 1 15

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. Data will be included in the next FluWatch report (week 45).

Influenza Strain Characterizations

From September 1 to November 7, 2019, the National Microbiology Laboratory (NML) has characterized 28 influenza viruses (16 A(H3N2), 5 A(H1N1) and 7 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:

Genetic Characterization:

All 16 A(H3N2) viruses this season have been genetically characterized, based on sequence analysis of the HA gene.

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)

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

Influenza B

Of the seven influenza B viruses antigenically characterized this season:

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:

24 influenza viruses (13 A(H3N2), 5 A(H1N1) and 6 B) were tested for resistance to oseltamivir:

Zanamivir:

24 influenza viruses (13 A(H3N2), 5 A(H1N1) and 6 B) were tested for resistance 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

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.

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