FluWatch report: October 7, 2018 to October 13, 2018 (Week 41)

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Organization: Public Health Agency of Canada

Date published: 2018-10-19

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Overall Summary

  • Influenza activity remains at interseasonal levels across the country.
  • The majority of regions in Canada report no influenza activity.
  • All indicators of influenza activity are at low levels, as expected for this time of year.
  • Influenza A is the most common influenza virus circulating in Canada.
  • Influenza and other respiratory viruses are monitored weekly and results reported every Thursday in the Respiratory Virus Detections in Canada Report

Influenza/Influenza-like Illness Activity (geographic spread)

During week 41, the following influenza activity levels were reported (Figure 1):

  • No regions reported localized activity.
  • Sporadic activity was reported by 12 regions, in Alta.(2), Sask. (2), Man. (1), Ont.(2), Que.(3), N.B. (1), and N.L. (1).
  • No activity was reported by the majority of regions (39).
  • No data were reported by two regions.

Figure 1 – Map of overall influenza/ILI activity by province and territory, Canada, week 2018-41

Figure 1
Figure 1 - Text Description
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 No Activity
N.S. Zone 4 - Central No Activity
N.B. Region 1 No Activity
N.B. Region 2 Sporadic
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 Sporadic
Que. Montréal et Laval Sporadic
Que. Ouest-du-Québec No Activity
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 Activity
Ont. South West No Activity
Ont. Toronto No Activity
Man. Northern Regional No Activity
Man. Prairie Mountain No Activity
Man. Interlake-Eastern No Activity
Man. Winnipeg Sporadic
Man. Southern Health No Activity
Sask. North No Activity
Sask. Central Sporadic
Sask. South Sporadic
Alta. North Zone No Activity
Alta. Edmonton Sporadic
Alta. Central Zone No Activity
Alta. Calgary Sporadic
Alta. South Zone No Activity
B.C. Interior No Activity
B.C. Fraser No Activity
B.C. Vancouver Coastal No Activity
B.C. Vancouver Island No Activity
B.C. Northern No Activity
Y.T. Yukon No Activity
N.W.T. North No Data
N.W.T. South No Data
Nvt. Qikiqtaaluk No Activity
Nvt. Kivalliq No Activity
Nvt. Kitimeot No Activity

Laboratory Confirmed Influenza Detections

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

  • Overall, laboratory detections of influenza are at interseasonal levels.
  • A total of 57 laboratory detections of influenza were reported. Fifty-four of these detections were influenza A.
  • The percentage of tests positive for influenza was 1.65% in week 41.

To date this season 182 laboratory-confirmed influenza detections have been reported (Figure 3):

  • 93% have been influenza A

To date this season, detailed information on age and type/subtype has been received for 124 laboratory-confirmed influenza cases (Table 1):

  • Adults 20-64 years of age represent the largest proportion of cases overall (57%)

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, 2018-35 to 2018-41

Figure 2

The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the start and end of seasonal influenza activity.

Figure 2 - Text Description
Surveillance Week A(Unsubtyped) A(H3) A(H1)pdm09 Influenza B
35 3 2 7 0
36 4 7 4 0
37 3 2 3 1
38 6 3 2 3
39 11 5 1 3
40 16 7 29 3
41 28 5 21 3

Figure 3 – Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, weeks 2018-35 to 2018-41

Figure 3
Figure 3 - Text Description
Reporting
provincesTable Figure 3 - Footnote 1
Week (October 7, 2018 to October 13, 2018) Cumulative (August 26, 2018 to October 13, 2018)
Influenza A B Influenza A B A & B
Total
A
Total
A
(H1N1)pdm09
A
(H3N2)
A(UnS)Table Figure 3 - Footnote 3 B
Total
A
Total
A
(H1N1)pdm09
A
(H3N2)
A(UnS)Table Figure 3 - Footnote 3 B
Total
BC 4 0 2 2 0 30 6 10 14 1 31
AB 25 17 1 7 1 65 35 12 18 7 72
SK 0 0 0 0 0 7 0 2 5 0 7
MB 3 3 0 0 0 5 5 0 0 0 5
ON 6 0 1 5 0 23 9 6 8 3 26
QC 7 0 0 7 2 13 0 0 13 2 15
NB 1 0 0 1 0 2 0 0 2 0 2
NS 0 0 0 0 0 0 0 0 0 0 0
PE 0 0 0 0 0 0 0 0 0 0 0
NL 1 0 0 1 0 1 0 0 1 0 1
YT 0 0 0 0 0 0 0 0 0 0 0
N.W.T 0 0 0 0 0 0 0 0 0 0 0
NU 0 0 0 0 0 0 0 0 0 0 0
Canada 47 20 4 23 3 146 55 30 61 13 159
PercentageTable Figure 3 - Footnote 2 94% 43% 9% 49% 6% 92% 38% 21% 42% 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

Table Figure 3 - Footnote UnS

Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available.

Return to first Table Figure 3 - Footnote 3 referrer

Discrepancies in values in Figures 2 and 3 may be attributable to differing data sources.

Cumulative data includes updates to previous weeks.

Table 1 - Cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reporting, Canada, weeks 2018-35 to 2018-41
Age groups (years) Cumulative (August 26, 2018 to October 13, 2018)
Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) A (UnS)Footnote 1 Total # %
0-4 >17 7 <5 10 0 - -
5-19 12 7 0 5 <5 - -
20-44 >30 18 <5 12 <5 - -
45-64 31 12 7 12 <5 - -
65+ >13 <5 8 <5 <5 - -
Total 112 49 >15 >39 12 - -
Tableau 1 - Note 1

UnS: unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available;

Return to Table 1 - Note 1

Syndromic/Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 41, 1.5% of visits to healthcare professionals were due to influenza-like illness (ILI) (Figure 4). The percentage of visits for ILI is at interseasonal levels.

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2018-35 to 2018-41

Number of Sentinels Reporting in Week 41: 90

The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2013-14 to 2017-18

Figure 4
Figure 4 - Text Description
Report week 2018-19 Average Min Max
35 0.6% 0.6% 0.4% 0.9%
36 0.7% 0.8% 0.5% 1.0%
37 0.6% 0.9% 0.7% 1.1%
38 0.5% 1.0% 0.7% 1.4%
39 1.8% 1.1% 0.8% 1.5%
40 0.8% 1.6% 0.9% 3.4%
41 1.5% 1.6% 1.1% 2.1%

Participatory Syndromic Surveillance

In week 41, 1,959 participants reported to FluWatchers, of which 48 (2.5%) reported symptoms of cough and fever (Figure 5).

Among the 48 participants who reported fever and cough:

  • 25% consulted a healthcare professional
  • 77% reported days missed from work or school, resulting in a combined total of 90 missed days of work or school.

Figure 5 – Percentage of participants reporting cough and fever, Canada, week 2018-41

Number of Participants Reporting in Week 41: 1,959

Figure 5
Figure 5 - Text Description
Report week % cough and Fever
40 2.6%
41 2.5%

Influenza Outbreak Surveillance

In week 41, one new laboratory-confirmed influenza outbreak was reported in a long-term care facility. To date this season, 3 influenza outbreaks have been reported. All reported outbreaks were influenza A.

No new ILI outbreaks were reported in week 41. To date this season, 17 ILI outbreaks have been reported. All outbreaks occurred in LTC facilities.

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 16 influenza-associated hospitalizations were reported by participating provinces and territoriesFootnote 1.

  • 88% were associated with influenza A
  • 63% were in adults 20-64 years of age

To date this season <5 ICU admissions and <5 deaths have been reported.

Pediatric Influenza Hospitalizations and Deaths

To date this season, <5 pediatric hospitalizations have been reported by the Immunization Monitoring Program Active (IMPACT) network.

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 2018-19 season.

Influenza Strain Characterizations

Since September 1, 2018, the National Microbiology Laboratory (NML) has characterized 5 influenza viruses (2 A(H3N2) and 3 A(H1N1)) that were received from Canadian laboratories.

Genetic Characterization of Influenza A (H3N2):

One influenza A(H3N2) virus did not grow to sufficient hemagglutination titer for antigenic characterization by hemagglutination inhibition (HI) assay. Therefore, NML has performed genetic characterization to determine the genetic group identity of this virus.

Sequence analysis of the HA gene of this virus showed that:

  • The A(H3N2) virus belonged to genetic group 3C.2a1
  • A/Singapore/INFIMH-16-0019/2016-like virus belongs to genetic group 3C.2a1 and is the influenza A(H3N2) component of the 2018-19 Northern Hemisphere influenza vaccine

Antigenic Characterization:

Influenza A(H3N2):

  • One influenza A(H3N2) virus was antigenically characterized as A/Singapore/INFIMH-16-0019/2016-like by HI testing using antiserum raised against egg-propagated A/Singapore/INFIMH-16-0019/2016.
  • A/Singapore/INFIMH-16-0019/2016 is the influenza A(H3N2) component of the 2018-19 Northern Hemisphere influenza vaccine.

Influenza A(H1N1):

  • Three A(H1N1) viruses characterized were antigenically similar to A/Michigan/45/2015, which is the influenza A(H1N1) component of the 2018-19 Northern Hemisphere influenza vaccine.

Antiviral Resistance

Antiviral Resistance – Amantadine:

Four influenza A (2 A(H3N2) and 2 A(H1N1)) viruses were tested for resistance to amantadine and it was found that:

  • The two A(H3N2) viruses tested were resistant to amantadine.
  • The two A(H1N1) virus tested were resistant to amantadine.

Antiviral Resistance – Oseltamivir:

Five influenza viruses (2 A(H3N2) and 3 A(H1N1)) were tested for resistance to oseltamivir and it was found that:

  • The two A(H3N2) viruses tested were sensitive to oseltamivir
  • The three A(H1N1) viruses tested were sensitive to oseltamivir

Antiviral Resistance – Zanamivir:

Five influenza viruses (2 A(H3N2) and 3 A(H1N1)) were tested for resistance to zanamivir and it was found that:

  • The two A(H3N2) viruses were sensitive to zanamivir.
  • The three A(H1N1) viruses were sensitive to zanamivir.

Notes: To learn more about definitions, descriptions and the FluWatch program in general, see the Overview of influenza monitoring in Canada page. For more information on the flu, see our Flu(influenza) web page.

This report is available on the Government of Canada Influenza webpage.
Ce rapport est disponible dans les deux langues officielles.

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

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