FluWatch report: October 6 to October 12, 2019 (Week 41)

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Organization: Public Health Agency of Canada

Date published: 2019-10-18

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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 increased in week 41.
  • 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 41, the number of regions reporting influenza activity increased. The following influenza activity levels were reported (Figure 1):

Figure 1 – Map of influenza/ILI activity by province and territory, Canada, week 2019-41

Number of Regions Reporting in Week 41: 53 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 No Activity
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 Sporadic
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 Sporadic
Que. Québec et Chaudieres-Appalaches No Activity
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 No Activity
Ont. Eastern No Activity
Ont. North East No Activity
Ont. North West No Activity
Ont. South West Sporadic
Ont. Toronto No Activity
Man. Northern Regional Sporadic
Man. Prairie Mountain No Activity
Man. Interlake-Eastern Sporadic
Man. Winnipeg No Activity
Man. Southern Health No Activity
Sask. North Sporadic
Sask. Central No Activity
Sask. South No Activity
Alta. North Zone No Activity
Alta. Edmonton Sporadic
Alta. Central Zone Sporadic
Alta. Calgary Localized
Alta. South Zone No Activity
B.C. Interior No Activity
B.C. Fraser Sporadic
B.C. Vancouver Coastal Sporadic
B.C. Vancouver Island Localized
B.C. Northern No Activity
Y.T. Yukon Sporadic
N.W.T. North No Activity
N.W.T. South No Activity
Nvt. Qikiqtaaluk No Activity
Nvt. Kivalliq Sporadic
Nvt. Kitimeot No Activity

Laboratory-Confirmed Influenza Detections

In week 41, the following results were reported from sentinel laboratories across Canada (Figures 2 and 3):

To date this season (weeks 35 to 41), detailed information on age and type/subtype has been received for 181 laboratory-confirmed influenza cases: 161 (89%) influenza A and 20 (11%) influenza B. Among the 86 subtyped influenza A detections, 92% of cases were A(H3N2). The majority of cases reported to date were in adults; 37% of cases were 20-64 years of age, and 46% were over 65 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 – Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, weeks 2019-35 to 2019-41

Number of Laboratories Reporting in Week 41: 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 35 9 0 2 1.2 0.1
41 39 13 0 3 1.6 0.1

Figure 3 – Distribution of positive influenza specimens by type/subtype and province/territory*, Canada, weeks 2019-35 to 2019-41

Figure 3. Text equivalent follows.

Figure 3 - Text equivalent
ProvincesTable Figure 3 - Footnote 1 Cumulative (August 25. 2019 to October 12, 2019)
A Total A(H1N1)pdm09 A(H3N2) A(UnS)3 B Total A & B Total
BC 100 4 45 29 0 100
AB 51 3 34 14 6 57
SK 14 0 0 8 0 14
MB 2 0 0 2 2 4
ON 27 1 15 11 7 34
QC 47 0 0 47 6 53
NB 4 1 1 2 1 5
NS 0 0 0 0 1 1
PEI 0 0 0 0 0 0
NL 0 0 0 0 0 0
YT 8 0 9 3 0 8
N.W.T 0 0 0 0 0 0
NU 0 0 0 0 0 0
Canada 253 9 104 116 23 276
PercentageTable Figure 3 - Footnote 2 92% 4% 41% 46% 8% 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

Syndromic / Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 41, 1.1%, 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).

Figure 4 – Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2019-35 to 2019-41

Number of Sentinels Reporting in Week 41: 82

Figure 4. Text equivalent follows.

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 1.1% 1.7% 0.8% 2.8%

FluWatchers

FluWatchers reporting for the 2019-20 season began on October 7th, 2019.

In week 41, 2,762 participants reported to FluWatchers, of which 46 (1.7%) reported symptoms of cough and fever (Figure 5).

Among the 46 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, weeks 2019-40 to 2019-41

Number of Participants Reporting in Week 41: 2,762

Figure 5. Text equivalent follows.
Figure 5 - Text equivalent
Surveillance Week % cough and fever
40 2.1%
41 1.7%

Online Figure – Geographic distribution of FluWatchers participants reporting cough and fever, Canada, week 2019-41

Click on the map to access the link

map

Influenza Outbreak Surveillance

In week 41, two laboratory-confirmed influenza A outbreak were reported; one in a long-term care facility and one in another type of facility. No ILI outbreaks were reported.

To date this season, a total of 6 laboratory-confirmed influenza outbreaks have been reported; five in long-term care facilities and one in another type of facility. Two ILI outbreaks in schools and daycares have also been reported.

Number of provinces and territories reporting in week 41: 13 out of 13

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 41, less than five influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote 1.

To date this season. 17 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote 1.

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

Number of provinces and territories reporting in week 41: 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 week41, two pediatric (≤16 years of age) laboratory-confirmed influenza-associated hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network.

To date this season, five pediatric hospitalizations have been reported by the IMPACT network; three cases associated with influenza A and two with influenza B.

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 17, 2019, the National Microbiology Laboratory (NML) has characterized 8 influenza viruses (5 A(H3N2), 1 A(H1N1) and 2 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 five 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

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 :

Zanamivir:

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

Amantadine:

High levels of resistance to amantadine persist among influenza A(H1N1) and influenza A(H3N2) viruses. therefore amantadine resistance results are not presented.

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.

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