FluWatch report: January 25 to January 31, 2015 (Week 4)
- In week 4, all influenza indicators continue to decline indicating that peak of the influenza season in Canada has passed.
- A(H3N2) continues to be the most common type of influenza affecting Canadians. In both laboratory detections, hospitalizations and deaths and the majority of cases have been among seniors ≥65 years of age.
- Detections of respiratory syncytial virus (RSV) continue to be the second most frequently detected virus after influenza. Since week 38, detections of RSV have been higher than in the previous season.
- On February 5, 2015, a Canadian interim vaccine effectiveness (VE) study by the PCIRN-SOS Network was published in Eurosurveillance. This study which examined VE for those seriously ill and in hospital found the overall VE for those under 65 years of age to be 11% and minus 25% for those over 65 years of age. Almost all (99%) cases were laboratory confirmed with H3N2. These poor VE estimates are not unexpected given the high degree of drift of the circulating virus from the vaccine strain observed in Canada this season.
- Evidence from the National Microbiology Laboratory does indicate that the other vaccine components will continue to provide protection against the circulating A(H1N1) and B strains.
Are you a primary health care practitioner (General Practitioner, Nurse Practitioner or Registered Nurse) interested in becoming a FluWatch sentinel for the 2014-15 influenza season? Contact us at FluWatch@phac-aspc.gc.ca
On this page
- Influenza/ILI Activity (geographic spread)
- Influenza and Other Respiratory Virus Detections
- Antiviral Resistance
- Influenza Strain Characterizations
- Influenza-like Illness (ILI) Consultation Rate
- Influenza Outbreak Surveillance
- Pharmacy surveillance
- Sentinel Hospital Influenza Surveillance
- Provincial/Territorial Influenza Hospitalizations and Deaths
- Emerging Respiratory Pathogens
- International Influenza Reports
Influenza/ILI Activity (geographic spread)
In week 04, 6 regions reported widespread activity: in ON(3), QC(2), NF. Twenty-seven regions reported localized activity: in BC(4), SK, MB, ON(4), QC(3), NB(6), NS(6), NL and PEI and fifteen regions reported sporadic activity: in NWT, YK, BC, SK(2), MB(4), QC, NB, NS(2) and NF(2). NU and AB did not report data for week 04.
Influenza and Other Respiratory Virus Detections
The number of positive tests decreased from 2,959 in week 03 to 2,388 in week 04. The percentage of positive influenza tests also decreased from 28.3% to 25.0% (Figure 2). To date, 97% of influenza detections have been influenza A, and 99.8% of those subtyped have been A(H3N2). (Table 1). To date this season, detailed information on age and type/subtype has been received for 25,918 cases. A significantly greater proportion of laboratory detections of influenza have been reported in adults ≥65 years of age (62%) this season (Table 2) compared to the 2013-14 season when only 15.5% of cases were in adults ≥65 years of age.
In week 04, the number of positive respiratory syncytial virus (RSV) tests decreased to 936 RSV detections and remains the second most frequently detected virus after influenza. Detections of RSV since week 38 have been higher than in the previous season. During the past few weeks detections of other respiratory viruses have been relatively stable. Detections of other respiratory viruses have generally been lower this season compared to the previous season (figure 3).
For more details, see the weekly Respiratory Virus Detections in Canada Report.
|Reporting provincesFootnote 1||Weekly (January 25 to January 31, 2015)||Cumulative (August 24, 2014 to January 31, 2015)|
|Influenza A||B||Influenza A||B|
|A Total||A(H1)pdm09||A(H3)||A Footnote (Uns)||B Total||A Total||A(H1)pdm09||A(H3)||A(UnS)||B Total|
|Percentage Footnote 2||93.6%||0.2%||40.6%||59.3%||6.4%||96.6%||0.1%||36.9%||63.0%||3.4%|
|Age groups (years)||Weekly January 25 to January 31, 2015||Cumulative (August 24, 2014 to January 31, 2015)|
|Influenza A||B||Influenza A||B||Influenza A and B|
|A Total||A(H1) pdm09||A(H3)||A Footnote (Uns)||Total||A Total||A(H1) pdm09||A(H3)||A (UnS)||Total||#||%|
During the 2014-2015 influenza season, the NML has tested 425 influenza viruses for resistance to oseltamivir and 424 influenza viruses for resistance to zanamivir and all were sensitive to both agents. A total of 692 (99.8%) influenza viruses were resistant to amantadine (Table 3).
|Virus type and subtype||Oseltamivir||Zanamivir||Amantadine|
|# tested||# resistant (%)||# tested||# resistant (%)||# tested||# resistant (%)|
|A (H3N2)||352||0||351||0||691||690 (99.9%)|
|A (H1N1)||2||0||2||0||2||2 (100%)|
|B||71||0||71||0||NATable 3 - Footnote *||NA Table 3 - Footnote *|
Influenza Strain Characterizations
During the 2014-2015 influenza season, the National Microbiology Laboratory (NML) has characterized 151 influenza viruses [75 A(H3N2), 2 A(H1N1) and 74 influenza B].
Influenza A (H3N2): When tested by hemagglutination inhibition (HI) assay (n=75), one virus was antigenically similar to A/Texas/50/2012, five showed reduced titers to A/Texas/50/2012 and 69 were antigenically similar to A/Switzerland/9715293/2013, which is the influenza A(H3N2) component recommended for the 2015 Southern Hemisphere influenza vaccine. Additionally, 538 A(H3N2) viruses were unable to be tested by HI assay; however, sequence analysis showed that 536 belonged to a genetic group that typically shows reduced titers to A/Texas/50/2012.
Influenza A(H1N1): Two A(H1N1) viruses characterized were antigenically similar to A/California/7/2009.
Influenza B: Of the 74 influenza B viruses characterized, 67 viruses were antigenically similar to B/Massachusetts/2/2012, three viruses showed reduced titers against B/Massachusetts/2/2012, and four were B/Brisbane/60/2008-like (Figure 4).
Figure 4. Influenza strain characterizations, Canada, 2014-2015, N = 151
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.
The recommended components for the 2014-2015 northern hemisphere trivalent influenza vaccine include: an A/California/7/2009(H1N1)pdm09-like virus, an A/Texas/50/2012 (H3N2)-like virus, and a B/Massachusetts/2/2012 -like virus (Yamagata lineage). For quadrivalent vaccines, the addition of a B/Brisbane/60/2008-like virus is recommended.
Figure 4 - Text Description
|Strain||Number of specimens||Percentage|
|reduced titres to A/Texas/50/2012||5||3%|
|reduced titres to B/Massachusetts/2/2012||3||2%|
Influenza-like Illness (ILI) Consultation Rate
The national influenza-like-illness (ILI) consultation remained relatively the same as the previous week at 66.8 consultations per 1,000, which is above expected levels (Figure 5).
Influenza Outbreak Surveillance
In week 04, 93 new outbreaks of influenza were reported, up from the number of outbreaks reported in the previous week. Sixty-four outbreaks were reported in long-term care facilities (LTCF), 13 in hospitals and 16 in institutional or community settings (Figure 6). An additional 17 outbreaks of ILI were reported in schools. Among the outbreaks in which the influenza subtype was known, eight LTCF outbreaks and one institutional or community setting outbreak were associated with A(H3N2). To date this season, 859 outbreaks in LTCFs have been reported and the majority of those with known subtypes were attributable to A(H3N2). There has been a higher number of reported influenza outbreaks to date this season compared to the same period in previous seasons.
Figure 6: Overall number of new laboratory-confirmed influenza outbreaks by report week, Canada, 2014-2015
1 All provinces and territories except NU report outbreaks in long-term care facilities. All provinces and territories with the exception of NU and QC report outbreaks in hospitals. Outbreaks of influenza or influenza-like-illness in other facilities are reported to FluWatch but reporting varies between jurisdictions. Outbreak definitions are included at the end of the report.
Figure 6 - Text Description
|Report week||Hospitals||Long Term Care Facilities||Other|
During week 04, the proportion of prescriptions for antivirals decreased to 395.7 antiviral prescriptions per 100,000 total prescriptions (down from 512.3 per 100,000). The rate for antivirals since week 48 has been higher than the previous three seasons (Figure 7). The rate in all age groups decreased in week 04. The antiviral prescription rate remains the highest amongst seniors at 650.0 per 100,000 total prescriptions.
Sentinel Hospital Influenza Surveillance
Paediatric Influenza Hospitalizations and Deaths (IMPACT)
In week 04, 23 laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network: 22 cases of influenza A and one case of influenza B (Figure 8a). Among the reported cases, 5 (22%) were <2 years of age, 13 (56%) were 2 to 9 years of age and five (22%) were 10-16 years of age. Two cases were admitted to the ICU. To date this season, 467 hospitalizations have been reported by the IMPACT network, 441 (94%) of which were cases of influenza A. Among cases for which the influenza A subtype was reported, 99% (139/141) were A(H3N2) (Table 4). To date, 53 cases were admitted to the ICU, of which 33 (60%) were 2 to 9 years of age (Figure 9a). Three deaths have been reported.
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.
Adult Influenza Hospitalizations and Deaths (PCIRN)
In week 04, 78 laboratory-confirmed influenza-associated adult (≥16 years of age) hospitalizations were reported by the PHAC/CIHR Influenza Research Network (PCIRN) Serious Outcomes Surveillance (SOS) network. Among the cases in week 04, 63 cases (81%) were in adults over the age of 65 and 74 cases (95%) had influenza A (Figure 8b). To date this season, 1,411 cases have been reported; 1,392 (99%) with influenza A. The majority of cases (83%) were among adults ≥65 years of age (Table 5). One hundred ICU admissions have been reported and 76 cases were adults ≥65 years of age. A total of 79 ICU cases reported to have at least one underlying condition or comorbidity. Of the 74 ICU cases with known immunization status, 24 (32%) reported not having been vaccinated this season. Sixty-four deaths have been reported, 57 (89%) of the deaths were adults >65 years of age (Figure 9B).
Note: The number of hospitalizations reported through PCIRN represents a subset of all influenza-associated adult hospitalizations in Canada. Delays in the reporting of data may cause data to change retrospectively.
|Age groups||Cumulative (Aug. 24, 2014 to January 31, 2015)|
|Influenza A||B||Influenza A and B|
|A Total||A(H1) pdm09||A(H3)||AFootnote (Uns)||Total||# (%)|
|% Footnote 1||94.4%||0.5%||31.5%||68.0%||5.6%||100.0%|
|Age groups||Cumulative (November 15, 2014 to January 31, 2015)|
|Influenza A||B||Influenza A and B|
|A Total||A(H1) pdm09||A(H3)||AFootnote (Uns)||Total||# (%)|
|% Footnote 1||99%||0%||34%||66%||1%||100%|
Figure 8 - Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2014-15
8A) Paediatric hospitalizations (≤16 years of age, IMPACT)
Figure 8A - Text Description
|Report week||Influenza A||Influenza B|
8B) Adult hospitalizations (≥16 year of age, PCIRN-SOS)
Note: Data for week 46 is based on data collected for 1 day only and do not represent the number of hospitalizations for the entire week.
Figure 8B - Text Description
|Report week||Influenza A||Influenza B||Untyped|
Figure 9 - Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada, 2014-15
9A) Paediatric hospitalizations (≤16 years of age, IMPACT)
Figure 9A - Text Description
|Age-group (years)||Hospitalizations(n=467)||ICU admissions(n=53)|
9B) Adult hospitalizations (≥16 year of age, PCIRN-SOS)
Figure 9B - Text Description
|Age-group (years)||Hospitalizations (n=1409)||ICU admissions(n=100)||Deaths (n=64)|
Provincial/Territorial Influenza Hospitalizations and Deaths
In week 04, 345 laboratory-confirmed influenza-associated hospitalizations were reported from participating provinces and territoriesFootnote *; all but six with influenza A, and 75% were patients ≥65 years of age. Since the start of the 2014-15 season, 4,079 hospitalizations have been reported; 4,001 (98%) with influenza A. Among cases for which the subtype of influenza A was reported, 99.7% (1930/1935) were A(H3N2). The majority of cases (71%) were ≥65 years of age (Table 6). A total of 120 ICU admissions have been reported in adults ≥65 years of age with influenza A and 63 ICU admissions have been reported in adults 20-64 years. A total of 275 deaths have been reported since the start of the season: three children <5 years of age, two children 5-19 years, 19 adults 20-64 years, and 251 adults ≥65 years of age. Adults 65 years of age or older represent 91% of all deaths reported this season. Detailed clinical information (e.g. underlying medical conditions) is not known for these cases.
|Age groups||Cumulative (24 August 2014 to 31 January 2015)|
|Influenza A||B||Influenza A and B|
|A Total||A(H1) pdm09||A(H3)||AFootnote (Uns)||Total||# (%)|
|0-4 years||285||2||110||173||4||289 (7%)|
|5-19 years||190||0||98||92||5||195 (5%)|
|20-44 years||200||1||109||90||7||207 (5%)|
|45-64 years||419||2||209||208||13||432 (11%)|
|65+ years||2855||0||1354||1521||45||2900 (71%)|
|Percentage Footnote 1||98.1%||0.1%||48.2%||51.6%||1.9%||100.0%|
See additional data on Reported Influenza Hospitalizations and Deaths in Canada: 2009-10 to 2014-15 on the Public Health Agency of Canada website.
Emerging Respiratory Pathogens
Human Avian Influenza
Influenza A(H7N9): On January 26, 2015, the first imported human case of avian influenza A (H7N9) from China was confirmed in Canada. A second case was confirmed on January 29, 2015. They traveled together to China and recently returned to Canada. All evidence regarding the Canadian cases indicates they were likely infected following exposure in China. They were not symptomatic during travel and only became ill after arrival in Canada. These are the first documented cases of H7N9 infection in humans in North America. The risk to Canadians of getting sick with H7N9 remains very low as evidence suggests that it does not transmit easily from person-to-person.
Since the last FluWatch report, one new laboratory-confirmed case of human infection with avian influenza A(H7N9) virus was reported by the World Health Organization. Globally to February, 3 2015, the WHO reported a total of 486 laboratory-confirmed human cases with avian influenza A(H7N9) virus, including 185 deaths.
Documents related to the public health risk of influenza A(H7N9), as well as guidance for health professionals and advice for the public is updated regularly on the following websites:
Influenza A(H5N6): Since the last FluWatch report, no new cases of human infection with avian influenza A (H5N6) virus from China has been reported by the World Health Organization. Globally to February 3, 2015, the WHO has been informed of a total of two cases of avian influenza A (H5N6) virus, including one death.
Middle East Respiratory Syndrome Coronavirus (MERS-CoV)
Since the last FluWatch report, 9 new laboratory-confirmed cases of MERS-CoV have been reported by the World Health Organization. Globally, from September 2012 to February 3, 2015, the WHO has been informed of a total of 965 laboratory-confirmed cases of infection with MERS-CoV, including 357 deaths. All cases have either occurred in the Middle East or have had direct links to a primary case infected in the Middle East. The public health risk posed by MERS-CoV in Canada remains low (see the PHAC Assessment of Public Health Risk).
Documents related to the public health risk of MERS-CoV, as well as guidance for health professionals and advice for the public is updated regularly on the following websites:
Avian Influenza A(H5)
The Canadian Food Inspection Agency (CFIA) is continuing its investigation into an outbreak of highly pathogenic avian influenza H5N2 virus in British Columbia's Fraser Valley. No new sites have been identified since December 19, 2014. Further information on the outbreak is provided on the following CFIA website.
Enterovirus D68 (EV-D68)
Information related to enterovirus D68, as well as guidance for health professionals and advice for the public is updated regularly:
International Influenza Reports
- World Health Organization influenza update
- World Health Organization FluNet
- WHO Influenza at the human-animal interface
- Centers for Disease Control and Prevention seasonal influenza report
- European Centre for Disease Prevention and Control - epidemiological data
- South Africa Influenza surveillance report
- New Zealand Public Health Surveillance
- Australia Influenza Report
- Pan-American Health Organization Influenza Situation Report
FluWatch definitions for the 2014-2015 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.
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.
- 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:
4 = Widespread:
Note: ILI data may be reported through sentinel physicians, emergency room visits or health line telephone calls.
We would like to thank all the Fluwatch surveillance partners who are participating in this year's influenza surveillance program.
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