FluWatch report: December 9, 2018 to December 15, 2018 (Week 50)
- Overall, influenza activity in Canada continued to increase in week 50.
- All indicators have increased or remained similar 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 majority of lab confirmations and hospitalizations have been among individuals under the age of 65.
- This is the last FluWatch report for the 2018 calendar year. The next report will be published on Friday, January 4, 2019 and will contain data for weeks 51 and 52.
On this page
- Influenza/ILI Activity (geographic spread)
- Laboratory Confirmed Influenza Detections
- Syndromic/Influenza-like Illness Surveillance
- Participatory Syndromic Surveillance
- Influenza Outbreak Surveillance
- Severe Outcomes Influenza Surveillance
- Antiviral Resistance
- Provincial and International Influenza Reports
Influenza/Influenza-like Illness Activity (geographic spread)
During week 50, influenza activity levels continued to increase (Figure 1):
- 13 regions reported localized activity: in Alta.(2), Sask.(2), Ont.(3), Que.(2), N.B.(2), N.S.(1), and N.W.T(1)
- Sporadic activity was reported by 34 regions: in B.C.(5), Alta.(4), Sask.(1), Man.(5), Ont.(4), Que.(4), N.B.(5), N.L.(2), P.E.I.(1), N.W.T(1), Nvt.(1) and Yt.(1).
- No activity was reported by 6 regions.
Laboratory Confirmed Influenza Detections
In week 50, the following results were reported from sentinel laboratories across Canada (Figure 2):
- The percentage of tests positive for influenza continued to increase to 22.8%.
- 1,869 laboratory detections of influenza were reported, of which 99% were influenza A.
To date this season 8,245 laboratory-confirmed influenza detections have been reported (Figure 3):
- 99% have been influenza A.
- Among the 4,024 influenza A viruses subtyped, 94% have been A(H1N1)pdm09.
- Provincial and territorial differences in influenza type/subtype distribution are observed.
To date this season, detailed information on age and type/subtype has been received for 7,914 laboratory-confirmed influenza cases (Table 1):
- 70% of all influenza A(H1N1)pdm09 detections have been reported in individuals younger than 45 years of age.
- 66% of all influenza A(H3N2) detections have been reported in adults 65 years of age and older.
Figure 2 – Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, weeks 2018-35 to 2018-50
The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the period of seasonal influenza activity.
Figure 3 – Cumulative numbers of positive influenza specimens by type/subtype and province/territory, Canada, weeks 2018-35 to 2018-50
|Age groups (years)||Cumulative (August 26, 2018 to December 15, 2018)|
|Influenza A||B||Influenza A and B|
|A Total||A(H1) pdm09||A(H3)||A (UnS)Footnote 1||Total||#||%|
Syndromic/Influenza-like Illness Surveillance
Healthcare Professionals Sentinel Syndromic Surveillance
In week 50, 1.5% 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 2018-50
Number of Sentinels Reporting in Week 50: 103
The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2013-14 to 2017-18
Participatory Syndromic Surveillance
In week 50, 2,210 participants reported to FluWatchers, of which 82 (3.7%) reported symptoms of cough and fever (Figure 5).
Among the 82 participants who reported fever and cough:
- 15% consulted a healthcare professional;
- 74% reported days missed from work or school, resulting in a combined total of 180 missed days of work or school.
Figure 5 – Percentage of participants reporting cough and fever, Canada, weeks 2018-40 to 2018-50
Number of Participants Reporting in Week 50: 2,210
Influenza Outbreak Surveillance
In week 50, 13 new laboratory-confirmed influenza outbreaks were reported: long-term care facilities (LTCF) (4), acute care facilities (3), schools (1), and other settings (5). One new ILI outbreak was also reported in week 50.
To date this season, 67 laboratory-confirmed influenza outbreaks have been reported (Figure 6):
- 30 outbreaks were in LTCF, 13 were in schools, 10 in acute care facilities, and 14 were in other settings.
- All of the 55 outbreaks for which the influenza type was available were associated with influenza A.
- Among the 41 outbreaks for which the influenza A subtype was available:
- 80% (33) were associated with influenza A(H1N1)pdm09;
- 20% (8) were associated with A(H3N2),
To date this season, 36 ILI outbreaks have been reported; 26 occurred in LTCF, seven in schools, and three in acute care facilities.
Figure 6 – Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2018-35 to 2018-50
Severe Outcomes Influenza Surveillance
Provincial/Territorial Influenza Hospitalizations and Deaths
To date this season, 864 influenza-associated hospitalizations have been reported by participating provinces and territoriesFootnote 1.
Hospitalizations (Table 2):
- 99% (861) were associated with influenza A
- The highest estimated rate of hospitalization is among children under 5 years of age.
Intensive Care Unit (ICU) cases and deaths:
- To date this season 118 ICU admissions and 22 deaths have been reported.
- 41% (48) of reported ICU admissions were in adults aged 45-64 years.
- All reported deaths were associated with influenza A(H1N1)pdm09.
|Age Groups||Cumulative (August 26, 2018 to December 15, 2018)|
|Influenza A||Influenza B||Rate per 100,000 population|
Pediatric Influenza Hospitalizations and Deaths
In week 50, 45 pediatric (≤16 years of age) hospitalizations with influenza have been reported by the Immunization Monitoring Program Active (IMPACT) network (Figure 7).
To date this season, 281 pediatric hospitalizations have been (Figure 8):
- 99% (278) of cases have been associated with influenza A.
- Among the 174 cases for which the influenza subtype was available, 172 (98.9%) were associated with A(H1N1)pdm09.
To date this season, 47 ICU admissions, and less than five deaths have been reported.
- 90% (41) of ICU admissions were in children under the age of 10
- 98% (46) of ICU admissions have been associated with influenza A.
Figure 7 – Number of pediatric (≤16 years of age) hospitalizations reported by the IMPACT network, by week, Canada, weeks 2018-35 to 2018-50
Figure 8 - Cumulative numbers of pediatric hospitalizations (≤16 years of age) with influenza by age-group reported by the IMPACT network, Canada, weeks 2018-35 to 2018-50
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, 55 hospitalizations have been reported:
- 49 (89%) were associated with influenza A.
- 29 cases (53%) were adults 65 years of age and older.
- The most commonly reported comorbidity among hospitalized cases was endocrine disorders, which were reported in 67.2% of hospitalized cases.
Figure 9 - Cumulative numbers of adult hospitalizations (>20 years of age) with influenza by age-group reported by CIRN, Canada, 2018-19, weeks 2018-44 to 2018-50
Influenza Strain Characterizations
Since September 1, 2018, the National Microbiology Laboratory (NML) has characterized 264 influenza viruses (29 A(H3N2), 221 A(H1N1) and 14 B) that were received from Canadian laboratories.
Genetic Characterization of Influenza A (H3N2):
24 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:
- Three viruses belonged to genetic group 3C.2a.
- 21 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.
- Five 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.
- Two influenza A (H3N2) viruses characterized belonged to genetic group 3C.2a1. Sequencing is pending for the remaining three viruses.
- 221 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 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).
- 14 influenza B viruses were 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 – Amantadine:
221 influenza A (20 A(H3N2) and 195 A(H1N1)) viruses were tested for resistance to amantadine and it was found that:
- All 221 influenza A viruses were resistant to amantadine.
Antiviral Resistance – Oseltamivir:
262 influenza viruses (28 A(H3N2), 220 A(H1N1) and 14 B) were tested for resistance to oseltamivir and it was found that:
- All 262 influenza viruses were sensitive to oseltamivir
Antiviral Resistance – Zanamivir:
191 influenza viruses (28 A(H3N2), 150 H1N1 and 13 B) were tested for resistance to zanamivir and it was found that:
- All 191 influenza viruses were sensitive to zanamivir.
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