FluWatch report: September 27 to October 10, 2015 (weeks 39 & 40)

Overall Summary

  • Overall, there is low influenza activity in Canada; however, influenza activity and detections are increasing, especially in BC and ON.
  • In weeks 39 and 40, five influenza outbreaks were reported, the majority were reported in long-term care facilities. To date this season, seven outbreaks have been reported, which is lower compared to the same period in the previous season.
  • To date, 19 hospitalizations have been reported from participating regions, which is similar to the number reported last year at this time.
  • For more information on the flu, see our Influenza (flu) web page.

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Organization: Public Health Agency of Canada

Date published: 2015-10-16

Are you a primary health care practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel for the 2015-16 influenza season? Contact us at FluWatch@phac-aspc.gc.ca

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Influenza/Influenza-like Illness Activity (geographic spread)

In week 40, sporadic and localized influenza activity were reported in the Western provinces, Ontario and in one region of Nova Scotia.

Figure 1. Map of overall influenza/ILI activity level by province and territory, Canada, Week 40

Figure 1
Figure 1 Legend

Note: Influenza/ILI activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates and reported outbreaks. Please refer to detailed definitions at the end of the report. Maps from previous weeks, including any retrospective updates, are available on the Flu Activity website.

Figure 1 - Text Description

In week 40, sporadic and localized influenza activity were reported in the Western provinces, Ontario and in one region of Nova Scotia.

Laboratory Confirmed Influenza Detections

The number of positive influenza tests increased over the two week period. In week 40, the percent positive for influenza detections remained low at 2.1%; however, this is the highest recorded value compared the previous five seasons during the same period (Figure 2).

Figure 2. Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2015-16

Figure 2
Figure 2 - Text Description

The number of positive influenza tests increased over the two week period. In week 40, the percent positive for influenza detections remained low at 2.1%.

Most jurisdictions have reported only sporadic numbers of influenza detections in recent weeks. The majority of detections in Canada have been reported from BC and ON, accounting for 88% of influenza detections in Canada in week 40. To date, 92% of influenza detections have been influenza A and the majority of those subtyped have been A(H3).

Figure 3. Cumulative numbers of positive influenza specimens by type/subtype and province, Canada, 2015-16

Figure 3

Note: Specimens from NT, YT, and NU are sent to reference laboratories in other provinces. Cumulative data includes updates to previous weeks.

Figure 3 - Text Description
Reporting provincesTable Figure 3 - Footnote 1 Weekly (October 4 to October 10, 2015) Cumulative (August 30, 2015 to October 10, 2015)
Influenza A B Influenza A B A & B Total
A Total A(H1)pdm09 A(H3) A Table Figure 3 - Footnote UnS B Total A Total A(H1)pdm09 A(H3) ATable Figure 3 - Footnote UnS B Total
BC 16 0 13 3 2 78 0 55 23 3 81
AB 3 1 0 2 1 24 4 17 3 4 28
SK 0 0 0 0 0 0 0 0 0 0 0
MB 1 0 0 1 1 1 0 0 1 1 2
ON 26 5 8 13 1 50 10 21 19 6 56
QC 1 0 0 1 0 9 0 0 9 1 10
NB 0 0 0 0 0 0 0 0 0 0 0
NS 1 0 1 0 0 1 0 1 0 0 1
PE 0 0 0 0 0 0 0 0 0 0 0
NL 0 0 0 0 0 2 0 2 0 0 2
YT 0 0 0 0 0 0 0 0 0 0 0
NT 0 0 0 0 0 0 0 0 0 0 0
NU 0 0 0 0 0 0 0 0 0 0 0
Canada 48 6 22 20 5 165 14 96 55 15 180
Percentage Table Figure 3 - Footnote 2 90.6% 12.5% 45.8% 41.7% 9.4% 91.7% 8.5% 58.2% 33.3% 8.3% 100.0%

Among cases with reported age, the largest proportion was in those ≥65 years of age (44%) (Table 1). Compared to the previous year during the same period, a greater proportion of cases in the 45-64 age group have been reported to date.

Table 1. Weekly and cumulative numbers of positive influenza specimens by type, subtype and age-group reported through case-based laboratory reportingTable 1 - Footnote 1, Canada, 2015-16
Age groups (years) Weekly (October 4 to October 10, 2015) Cumulative (August 30, 2015 to October 10, 2015)
Influenza A B Influenza A B Influenza A and B
A Total A(H1) pdm09 A(H3) A Table 1 - Footnote UnS Total A Total A(H1) pdm09 A(H3) A Table 1 - Footnote UnS Total # %
<5 0 0 0 0 0 6 1 5 0 1 7 4.5%
5-19 2 0 2 0 2 7 0 5 2 4 11 7.1%
20-44 2 1 0 1 1 18 4 8 6 3 21 13.6%
45-64 5 2 2 1 0 43 7 26 10 3 46 29.9%
65+ 15 0 8 9 0 66 0 46 20 2 68 44.2%
Unknown 1 0 1 0 0 1 0 1 0 0 1 0.6%
Total 25 3 13 9 3 141 12 91 38 13 154 100.0%
PercentageTable 1 - Footnote 2 89.3% 12.0% 52.0% 36.0% 10.7% 91.6% 8.5% 64.5% 27.0% 8.4%    

For additional data on other respiratory virus detections see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada website.

Influenza-like Illness Consultation Rate

The national influenza-like-illness (ILI) consultation rate decreased from 19.1 consultations per 1,000 patient visits in week 39 to 17.1 per 1,000 visits in week 40. In week 40, the highest ILI consultation rate was found in the 5-19 age group and the lowest was found in the ≥65 age group (Figure 4).

Figure 4. Influenza-like-illness (ILI) consultation rates by age group and week, Canada, 2015-16

Figure 4

Delays in the reporting of data may cause data to change retrospectively. In BC, AB, and SK, data is compiled by a provincial sentinel surveillance program for reporting to FluWatch. Not all sentinel physicians report every week.

Figure 4 - Text Description

Influenza-like illness consultation rate by age-group in week 40 for the 2015-16 season: Age 0-4: 6.87; Age 5-19: 51.31; Age 20-64: 11.02; Age 65+: 0.05

Influenza Outbreak Surveillance

In weeks 39 and 40, five new outbreaks of influenza were reported. Four outbreaks were reported in long-term care facilities, three of which were associated with influenza A(H3). The other outbreak was reported in an institutional or community setting and was also associated with influenza A(H3) (Figure 5). To date this season, seven outbreaks have been reported, which is lower compared to the same period in the previous season.

Figure 5. Overall number of new laboratory-confirmed influenza outbreaksFigure 5 - Footnote 1 by report week, Canada, 2015-2016

Figure 5
Figure 5 - Text Description
Report week Hospitals Long Term Care Facilities Other
35 0 0 0
36 0 0 0
37 1 1 0
38 0 0 0
39 0 2 0
40 0 2 1

Sentinel Pediatric Hospital Influenza Surveillance

Paediatric Influenza Hospitalizations and Deaths (IMPACT)

To date, less than five laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations have been reported by the Immunization Monitoring Program Active (IMPACT) network. The hospitalized cases were due to influenza A.

Figure 6. Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada, 2015-16, Paediatric hospitalizations (≤16 years of age, IMPACT)

Figure 6
Figure 6 - Text Description
Age-group (years) Hospitalizations (n=3) ICU Admissions (n=0)
0-5m 0.0% 0.0%
6-23m 0.0% 0.0%
2-4y 0.0% 0.0%
5-9y 0.0% 0.0%
10-16y 0.0% 0.0%

Figure 7. Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2015-16 Paediatric hospitalizations (≤16 years of age, IMPACT)

Figure 7

Note: The number of hospitalizations reported through IMPACT represents a subset of all influenza-associated paediatric hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.

Figure 7 - Text Description
Report week Influenza A Influenza B
35 0 0
36 0 0
37 0 0
38 0 0
39 0 0
40 0 0

Provincial/Territorial Influenza Hospitalizations and Deaths

Since the start of the 2015-16 season, 19 laboratory-confirmed influenza-associated hospitalizations were reported from participating provinces and territoriesFootnote *. All were due to influenza A and the majority were patients ≥65 years of age. Two ICU admissions have also been reported.

Figure 8. Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada 2015-16

Figure 8
Figure 8 - Text Description
Age-group (years) Hospitalizations (n=19) ICU admissions (n=2) Deaths (n=0)
0-4 5.3% 0.0% 0.0%
5-19 0.0% 0.0% 0.0%
20-44 21.1% 50.0% 0.0%
45-64 21.1% 50.0% 0.0%
65+ 52.6% 0.0% 0.0%

See additional data on Reported Influenza Hospitalizations and Deaths in Canada: 2011-12 to 2015-16 on the Public Health Agency of Canada website.

Influenza Strain Characterizations

During the 2015-16 influenza season, the National Microbiology Laboratory (NML) has characterized five influenza viruses [5 A(H3N2)]. Sequence analysis of the HA gene of these viruses showed that the five H3N2 viruses were almost identical to the A/Switzerland/9715293/2013, the influenza A(H3N2) component of the 2015-16 influenza vaccine.

Figure 9. Influenza strain characterizations, Canada, 2015-16

The National Microbiology Laboratory (NML) has not yet conducted antigenic characterization of influenza viruses collected during the 2015-16 season.

The recommended components for the 2015-2016 northern hemisphere trivalent influenza vaccine include: an A/California/7/2009(H1N1)pdm09-like virus, an /Switzerland/9715293/2013(H3N2)-like virus, and a B/Phuket/3073/2013 -like virus (Yamagata lineage). For quadrivalent vaccines, the addition of a B/Brisbane/60/2008-like virus is recommended.

The NML receives a proportion of the number of influenza positive specimens from provincial laboratories for strain characterization and antiviral resistance testing. Characterization data reflect the results of haemagglutination inhibition (HAI) testing compared to the reference influenza strains recommended by WHO.

Antiviral Resistance

During the 2015-16 season, the National Microbiology Laboratory (NML) as tested five influenza viruses for resistance to oseltamivir and zanamivir. All viruses were sensitive to zanamivir and oseltamivir. All influenza A viruses tested were resistant to amantadine (Table 2).

Table 2. Antiviral resistance by influenza virus type and subtype, Canada, 2015-16
Virus type and subtype Oseltamivir Zanamivir Amantadine
# tested # resistant (%) # tested # resistant (%) # tested # resistant (%)
A (H3N2) 5 0 5 0 5 5 (100%)
A (H1N1) 0 0 0 0 0 0
B 0 0 0 0 NA Table 2 - Footnote * NA Table 2 - Footnote *
TOTAL 5 0 5 0 5 5

International Influenza Reports


FluWatch definitions for the 2015-2016 season

Abbreviations: Newfoundland/Labrador (NL), Prince Edward Island (PE), New Brunswick (NB), Nova Scotia (NS), Quebec (QC), Ontario (ON), Manitoba (MB), Saskatchewan (SK), Alberta (AB), British Columbia (BC), Yukon (YT), Northwest Territories (NT), Nunavut (NU).

Influenza-like-illness (ILI): Acute onset of respiratory illness with fever and cough and with one or more of the following - sore throat, arthralgia, myalgia, or prostration which is likely due to influenza. In children under 5, gastrointestinal symptoms may also be present. In patients under 5 or 65 and older, fever may not be prominent.

ILI/Influenza outbreaks

Schools:
Greater than 10% absenteeism (or absenteeism that is higher (e.g. >5-10%) than expected level as determined by school or public health authority) which is likely due to ILI.
Note: it is recommended that ILI school outbreaks be laboratory confirmed at the beginning of influenza season as it may be the first indication of community transmission in an area.
Hospitals and residential institutions:
two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case. Institutional outbreaks should be reported within 24 hours of identification. Residential institutions include but not limited to long-term care facilities (LTCF) and prisons.
Workplace:
Greater than 10% absenteeism on any day which is most likely due to ILI.
Other settings:
two or more cases of ILI within a seven-day period, including at least one laboratory confirmed case; i.e. closed communities.

Note that reporting of outbreaks of influenza/ILI from different types of facilities differs between jurisdictions.

Influenza/ILI activity level

1 = No activity: no laboratory-confirmed influenza detections in the reporting week, however, sporadically occurring ILI may be reported

2 = Sporadic: sporadically occurring ILI and lab confirmed influenza detection(s) with no outbreaks detected within the influenza surveillance region Footnote

3 = Localized:

  1. evidence of increased ILIFootnote * and
  2. lab confirmed influenza detection(s) together with
  3. outbreaks in schools, hospitals, residential institutions and/or other types of facilities occurring in less than 50% of the influenza surveillance regionFootnote

4 = Widespread:

  1. evidence of increased ILIFootnote * and
  2. lab confirmed influenza detection(s) together with
  3. outbreaks in schools, hospitals, residential institutions and/or other types of facilities occurring in greater than or equal to 50% of the influenza surveillance regionFootnote

Note: ILI data may be reported through sentinel physicians, emergency room visits or health line telephone calls.

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