FluWatch report: November 4, 2018 to November 10, 2018 (Week 45)

thumbnail

Download the alternative format
(PDF format, 815 KB, 7 pages)

Organization: Public Health Agency of Canada

Date published: 2018-11-16

Related Topics

Overall Summary

  • Influenza activity continued to increase in week 45. The influenza season has started earlier  than in recent years.The  number of regions in Canada reporting sporadic or localized influenza activity in week 45 increased slightly compared to the previous week.
  • Influenza A is the most common influenza virus circulating in Canada, and the majority of these viruses are A(H1N1)pdm09.
  • The number of influenza-associated hospitalizations continued to increase in week 45. In particular, the number of pediatric hospitalizations is significantly higher than in recent years.
  • The number of influenza outbreaks remains within expected levels. However, the settings in which outbreaks have been reported this season suggests that younger age-groups are being affected more than in previous seasons.

Influenza/Influenza-like Illness Activity (geographic spread)

During week 45, the following influenza activity levels increased slightly compared to the previous week (Figure 1):

  • Two regions in Alta. and Ont. reported localized activity.
  • Sporadic activity was reported by 28 regions, in B.C.(4), Alta.(4), Sask.(3), Man.(3), Ont.(4), Que.(5), N.S.(1), N.B.(1), P.E.I.(1), N.W.T(1) and Nvt.(1).
  • No activity was reported by 23 regions.

Figure 1 – Map of overall influenza/ILI activity by province and territory, Canada, week 2018-45

Figure 1
Figure 1 - Text description
Province Influenza Surveillance Region Activity Level
N.L. Eastern No Activity
N.L. Labrador-Grenfell No Activity
N.L. Central No Activity
N.L. Western No Activity
P.E.I. Prince Edward Island Sporadic
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 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 Sporadic
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 No Activity
Ont. South West Sporadic
Ont. Toronto Localized
Man. Northern Regional No Activity
Man. Prairie Mountain Sporadic
Man. Interlake-Eastern Sporadic
Man. Winnipeg Sporadic
Man. Southern Health No Activity
Sask. North Sporadic
Sask. Central Sporadic
Sask. South Sporadic
Alta. North Zone Sporadic
Alta. Edmonton Sporadic
Alta. Central Zone Sporadic
Alta. Calgary Localized
Alta. South Zone Sporadic
B.C. Interior Sporadic
B.C. Fraser Sporadic
B.C. Vancouver Coastal Sporadic
B.C. Vancouver Island Sporadic
B.C. Northern No Activity
Y.T. Yukon No Activity
N.W.T. North No Activity
N.W.T. South Sporadic
Nvt. Qikiqtaaluk No Activity
Nvt. Kivalliq No Activity
Nvt. Kitimeot Sporadic

Laboratory Confirmed Influenza Detections

In week 45, the following results were reported from sentinel laboratories across Canada (Figure 2):

  • The percentage of tests positive for influenza continued to increase to 9.6% of tests positive.
  • The percentage of tests positive for influenza A is higher for this time of year compared to the same period during the previous eight seasons. Laboratory detections of influenza have entered seasonal levels three weeks earlier than the median over the previous eight seasons.
  • In week 45, 509 laboratory detections of influenza were reported, of which 97% were influenza A.

To date this season 1,523 laboratory-confirmed influenza detections have been reported (Figure 3):

  • 97% have been influenza A
  • Among the 922 influenza A viruses subtyped, 80% have been A(H1N1)pdm09

To date this season, detailed information on age and type/subtype has been received for 1,457 laboratory-confirmed influenza cases (Table 1):

  • Adults 20-44 years of age represent the largest proportion of cases (25%), followed by adults >65 years of age (20%).

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 2018-45

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 27 6 21 3
42 40 19 55 2
43 83 23 128 4
44 170 13 213 6
45 201 17 276 15

Figure 3 – Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, weeks 2018-35 to 2018-45

Figure 3
Figure 3 - Text description
Reporting
provincesTable Figure 3 - Footnote 1
Week (October 28, 2018 to November 10, 2018) Cumulative (August 26, 2018 to November 10, 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 9 7 2 0 0 92 34 36 22 2 94
AB 371 235 4 132 1 877 547 28 302 11 888
SK 32 11 0 21 0 140 78 3 59 0 140
MB 16 4 0 12 0 57 41 2 14 0 57
ON 27 10 11 6 12 183 31 117 35 19 202
QC 47 0 0 47 1 120 0 0 120 7 127
NB 0 0 0 0 0 4 1 0 3 0 4
NS 2 0 0 2 0 5 0 0 5 0 5
PEI 1 1 0 0 0 2 2 0 0 0 2
NL 0 0 0 0 1 2 1 0 1 1 3
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 1 1 0 0 0 1 1 0 0 0 1
Canada 506 269 17 220 15 1483 736 186 561 40 1523
PercentageTable Figure 3 - Footnote 2 97% 53% 3% 43% 3% 97% 50% 13% 38% 3% 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 2018-45
Age groups (years) Cumulative (August 26, 2018 to November 10, 2018)
Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) A (UnS)Footnote 1 Total # %
0-4 >241 150 <5 91 <5 248 -
5-19 >266 159 <5 107 5 >271 -
20-44 365 193 12 160 8 373 -
45-64 263 137 25 101 6 269 -
65+ 282 106 116 60 10 292 -
Total >1264 745 >153 519 >29 >1293 -
Table 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 45, 2.0% of visits to healthcare professionals were due to influenza-like illness (ILI) (Figure 4). The percentage of visits for ILI is within expected levels.

Figure 4 - Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2018-35 to 2018-45

Number of Sentinels Reporting in Week 45: 90

Figure 4

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 - 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 0.6% 1.6% 0.9% 3.4%
41 1.1% 1.6% 1.1% 2.1%
42 1.2% 1.4% 0.8% 1.8%
43 1,0% 1,4% 0,7% 1,8%
44 0,9% 1,4% 1,1% 1,6%
45 2,0% 1,5% 1,2% 1,8%

Participatory Syndromic Surveillance

In week 45, 2,069 participants reported to FluWatchers, of which 35 (1.7%) reported symptoms of cough and fever (Figure 5).

Among the 35 participants who reported fever and cough:

  • 20% consulted a healthcare professional
  • 63% reported days missed from work or school, resulting in a combined total of 55 missed days of work or school.

Figure 5 – Percentage of participants reporting cough and fever, Canada, weeks 2018-40 to 2018-45

Number of Participants Reporting in Week 45: 2,069

Figure 5
Figure 5 - Text description
Surveillance week % cough and fever
40 2.6%
41 2.5%
42 1.7%
43 1.5%
44 1.3%
45 1.7%

Influenza Outbreak Surveillance

In week 45, five new laboratory-confirmed influenza outbreaks were reported in a long-term care facility (LTCF) (1), schools (3), and another type of facility (1).

To date this season, 18 influenza outbreaks have been reported (Figure 6): 

  • Eight outbreaks were in LTCF, six were in schools, and four were in other settings.
  • 15 of the 18 outbreaks were associated with influenza A.
  • Among the outbreaks for which the influenza A subtype was available:
    • Six were associated with influenza A(H1N1)pdm09, reported from schools and other settings;
    • Four were associated with A(H3N2), reported from LTCF and other settings;
    • Two were associated with both A(H1N1)pdm09 and A(H3N2), reported from LTCF.
  • Compared to previous seasons, a greater proportion of outbreaks have been reported in settings other than LTCF, suggesting an increased burden of disease in younger age-groups.

One new ILI outbreak in a LTCF was reported in week 45.

To date this season, 22 ILI outbreaks have been reported; 20 occurred in LTCF, one in a school, and one in a hospital.

Figure 6 – Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2018-35 to 2018-45

Figure 6
Figure 6 - Text description
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 0 0 0 0
40 0 2 0 1 0
41 0 0 0 0 0
42 0 1 1 0 0
43 0 1 1 0 0
44 0 0 1 2 0
45 0 1 1 3 0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 45, 65 influenza-associated hospitalizations were reported, which is an increase compared to the previous week.

To date this season, 218 influenza-assocaited hospitalizations have been reported by participating provinces and territoriesFootnote 1.

Hospitalizations (Table 2):

  • 99% (216) were associated with influenza A
  • Adults 65 years of age and older represent the largest proportion of hospitalizations (29%),  followed by adults 45-64 years of age (24%).

Intensive Care Unit (ICU) cases and deaths:

  • To date this season 28 ICU admissions and <5 deaths have been reported.
Table 2 – Cumulative number of hospitalizations by age-group reported by participating provinces and territoriesFootnote 1, Canada, weeks 2018-35 to 2018-45
Age Groups Cumulative (August 26, 2018 to November 10, 2018)
(years) Total %
0-4 37 17%
5-19 32 15%
20-44 34 16%
45-64 52 24%
65+ 63 29%
Total 218 100%

Pediatric Influenza Hospitalizations and Deaths

TIn week 45, 31 pediatric (≤16 years of age) hospitalizations with influenza have been reported by the Immunization Monitoring Program Active (IMPACT) network. Pediatric hospitalizations reported by IMPACT are at levels not normally seen until late December (4-6 weeks earlier than in recent seasons).

To date this season, 68 pediatric hospitalizations have been reported:

  • All 68 cases have been associated with influenza A.
  • Among the 51 for which the influenza subtype was available, 50 were associated with A(H1N1)pdm09.
  • 56 of the 68 cases (82%) were between 6 months and 9 years of age.

To date this season, 7 ICU admissions, and no deaths have been reported.

Figure 7 – Number of pediatric (≤16 years of age) hospitalizations reported by the IMPACT network, by week, Canada, weeks 2018-35 to 2018-45

Figure 7
Figure 7 - Text description
Surveillance week 2018-19 Average  Min Max
35 0 0 0 1
36 0 0 0 1
37 0 0 0 2
38 0 1 0 2
39 0 1 0 3
40 1 0 0 2
41 1 1 0 3
42 6 1 0 4
43 11 1 0 3
44 19 3 1 6
45 31 3 2 4

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 2018-19 season.

To date this season, six hospitalizations have been reported, of which five were associated with influenza A and one with influenza B.

Influenza Strain Characterizations

Since September 1, 2018, the National Microbiology Laboratory (NML) has characterized 43 influenza viruses (4 A(H3N2), 38 A(H1N1) and one B) that were received from Canadian laboratories.

Genetic Characterization of Influenza A (H3N2):

Three influenza A(H3N2) viruses 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 these viruses.

Sequence analysis of the HA gene of the viruses showed that:

  • One virus belonged to genetic group 3C.2a.
  • Two viruses belonged to subclade 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-like virus is the influenza A(H3N2) component of the 2018-19 Northern Hemisphere influenza vaccine.
  • The influenza A (H3N2) virus characterized belonged to genetic group 3C.2a1.

Influenza A(H1N1):

  • 38 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.

Influenza B:

Influenza B viruses can be divided into two antigenically distinct lineages represented by B/Yamagata/16/88 and B/Victoria/2/87 viruses. The recommended influenza B components  for the 2018-19 Northern Hemisphere influenza vaccine are  B/Colorado/06/2017 (Victoria lineage) and B/Phuket/3073/2013 (Yamagata lineage).

  • One influenza B viruses was characterized as B/Phuket/3073/2013-like, which belongs to the Yamagata lineage and is included as an influenza B component of the 2018-19 Northern Hemisphere quadrivalent influenza vaccine.

Antiviral Resistance

Antiviral Resistance – Amantadine:

23 influenza A (4 A(H3N2) and 19 A(H1N1)) viruses were tested for resistance to amantadine and it was found that:

  • The four A(H3N2) viruses tested were resistant to amantadine.
  • The 19 A(H1N1) viruses tested were resistant to amantadine.

Antiviral Resistance – Oseltamivir:

49 influenza viruses (9 A(H3N2), 39 A(H1N1) and 1 B) were tested for resistance to oseltamivir and it was found that:

  • The 9 A(H3N2) viruses tested were sensitive to oseltamivir
  • The 39 A(H1N1) viruses tested were sensitive to oseltamivir
  • The B virus was sensitive to oseltamivir

Antiviral Resistance – Zanamivir:

48 influenza viruses (9 A(H3N2), 38 H1N1 and 1 B) were tested for resistance to zanamivir and it was found that:

  • The 9 A(H3N2) viruses were sensitive to zanamivir.
  • The 38 A(H1N1) viruses were sensitive to zanamivir.
  • The B virus was 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.

Report a problem or mistake on this page
Please select all that apply:

Thank you for your help!

You will not receive a reply. For enquiries, contact us.

Date modified: