FluWatch report: December 14 to December 20, 2014 (Week 51)

Influenza/ILI Activity (geographic spread)

In week 51, eight regions reported widespread activity [in BC, AB(4), ON, QC(2)], 17 regions reported localized activity [in BC, AB, SK(2), MB(4) ON(5), QC(3), NS], and 12 regions [in NT, YK, BC(3), SK, MB, ON, QC, NB(2), PE] reported sporadic activity (Figure 1).

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 Map of overall influenza/ILI activity level by province and territory, Canada, Week 30 - Text Description

In week 51, eight regions reported widespread activity [in BC, AB(4), ON, QC(2)], 17 regions reported localized activity [in BC, AB, SK(2), MB(4) ON(5), QC(3), NS], and 12 regions [in NT, YK, BC(3), SK, MB, ON, QC, NB(2), PE] reported sporadic activity. No data was reported from NL.

Influenza and Other Respiratory Virus Detections

In week 51, the number of positive influenza tests increased sharply to 2,833 influenza detections (29.1% of tests), predominantly due to influenza A (Figure 2). To date, 97% of influenza detections have been influenza A, and 99.8% of those subtyped have been A(H3) (Table 1). The timing of the season and predominant A(H3N2) subtype is similar to the pattern observed during the 2012-13 influenza season when percent positive for influenza peaked in week 52 (35%). To date, among the cases of influenza with reported age, the largest proportion was in adults ≥65 years of age (56%) (Table 2).

Figure 2 Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, 2014-15 - Text Description

In week 51, the number of positive influenza tests increased sharply to 2,833 influenza detections (29.1% of tests), predominantly due to influenza A.

In week 51, the number of positive RSV tests increased to 655 RSV detections and was the second most frequently detected virus, after influenza. Detections of parainfluenza and adenovirus also continue to follow their seasonal patterns of broad winter circulation (figure 3).

For more details, see the weekly Respiratory Virus Detections in Canada Report.

RSV: Respiratory syncytial virus; hMPV: Human metapneumovirus

Figure 3 Number of positive laboratory tests for other respiratory viruses by report week, Canada, 2014-15 - Text Description

In week 51, the number of positive RSV tests increased to 655 RSV detections and was the second most frequently detected virus, after influenza. Detections of parainfluenza and adenovirus also continue to follow their seasonal patterns of broad winter circulation.

Antiviral Resistance

During the 2014-2015 influenza season, NML has tested 123 influenza viruses for resistance to oseltamivir and zanamivir and all were sensitive to both agents. A total of 154 (99%) of influenza A viruses tested for amantadine resistance were resistant (Table 3).

Influenza Strain Characterizations

During the 2014-2015 influenza season, the National Microbiology Laboratory (NML) has characterized 59 influenza viruses [37 A(H3N2), 2 A(H1N1) and 20 influenza B]. Influenza A (H3N2): When tested by hemagglutination inhibition (HI) assay, 31 of the 37 A(H3N2) viruses characterized were antigenically similar to A/Switzerland/9715293/2013, which is the influenza A(H3N2) component recommended for the 2015 Southern Hemisphere influenza vaccine. One was antigenically similar to A/Texas/50/2012, which is the influenza A(H3N2) component recommended for the 2014-15 influenza vaccine. The remaining five A(H3N2)viruses showed reduced titer to A/Texas/50/2012. Additionally, 112 A(H3N2)viruses were unable to be tested by HI assay; however, sequence analysis showed that 111 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, which is the influenza A(H1N1) component recommended for the 2014-15 influenza vaccine. Influenza B: Of the 20 influenza B viruses characterized, 17 viruses were antigenically similar to the vaccine strain B/Massachusetts/2/2012. Three viruses showed reduced titers with antiserum produced against strains recommended for the seasonal influenza vaccine (Figure 4).

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 Influenza strain characterizations, Canada, 2014-2015, N = 23 - Text Description

Figure 4: Influenza strain characterizations, Canada, 2014-15, N = 59

Strain	Number of specimens	Percentage
A/Texas/50/2012-like	1	2%
reduced titres to A/Texas/50/2012	5	8%
A/California/07/2009-like	2	3%
A/Switzerland/97 15293/2013-like	31	53%
B/Massachusetts/2/2012-like	17	29%
reduced titres to B/Massachusetts/2/2012	3	5%
B/Brisbane/60/2008-like	0	0%

Influenza-like Illness (ILI) Consultation Rate

The national influenza-like-illness (ILI) consultation decreased in week 51 to 14.97 consultations per 1,000, which is below expected levels for week 51 (Figure 5).

No data available for mean rate for weeks 19 to 39 for the 1996-1997 through 2002-2003 seasons. Delays in the reporting of data may cause data to change retrospectively. The calculation of the average ILI consultation rate over 17 seasons was aligned with influenza activity in each season. 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 5 Influenza-like-illness (ILI) consultation rates by report week, compared to the 1996-97 through to 2012-13 seasons (with pandemic data suppressed), Canada, 2015-16 - Text Description

The national influenza-like-illness (ILI) consultation decreased in week 51 to 14.97 consultations per 1,000, which is below expected levels for week 51.

Influenza Outbreak Surveillance

In week 51, 125 new outbreaks of influenza were reported: 94 in long-term care facilities (LTCF), nine in hospitals and 22 in institutional or community settings (Figure 6). An additional five outbreaks of ILI were reported in schools. Among the outbreaks in which the influenza subtype was known, two LTCF outbreaks, two institutional or community setting outbreaks, and one hospital outbreak were associated with A(H3N2). To date this season, 235 outbreaks in LTCF have been reported. The number of outbreaks reported is similar to the number reported in week 51 during the 2012-13 influenza season when influenza A(H3N2) also predominated.

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 Overall number of new laboratory-confirmed influenza outbreaks by report week, Canada, 2015-2016 - Text Description

Figure 6: Overall number of new laboratory-confirmed influenza outbreaks by report week, Canada, 2014-2015

Report week	Hospitals	Long Term Care Facilities	Other
35	0	0	0
36	0	0	0
37	0	0	0
38	0	1	0
39	0	5	1
40	0	0	0
41	0	2	0
42	0	3	0
43	0	2	0
44	0	1	0
45	0	2	0
46	0	3	0
47	0	16	1
48	3	17	1
49	2	32	3
50	2	57	13
51	9	94	22

Pharmacy surveillance

During week 51, the proportion of prescriptions for antivirals increased to 328.5 antiviral prescriptions per 100,000 total prescriptions (up from 150.3 antiviral prescriptions per 100,000 total prescriptions from the previous week). The rate for antivirals is higher than the previous three seasons (Figure 7). The rates in all age groups increased from the previous week; however, the rate doubled among seniors (205.7 to 509.03 per 100,000 total prescriptions).

Note: Pharmacy sales data are provided to the Public Health Agency of Canada by Rx Canada Inc. and sourced from major retail drug chains representing over 2,500 stores nationwide (excluding Nunavut) in 85% of Health Regions. Data provided include the number of new antiviral prescriptions (for Tamiflu and Relenza) and the total number of new prescriptions dispensed by Province/Territory and age group. Age-groups: Infant: 0-2y, Child: 2-18y; Adult: 19-64y, Senior: ≥65y

Figure 7 Proportion of prescription sales for influenza antivirals by age-group and week, Canada, 2015-16 - Text Description

Proportion of antiviral prescriptions per 100,000 total prescriptions in week 51 for the current season compared to previous seasons:
2014-15: 328.5; 2013-14: 54.7; 2012-13: 142.1; 2011-12: 29.4
Proportion of antiviral prescriptions by age-group in week 51 for the 2014-15 season:
Infant: 194.2; child: 309.2; adult: 195.8; senior: 509.0

Sentinel Hospital Influenza Surveillance

Paediatric Influenza Hospitalizations and Deaths (IMPACT)

In week 51, 56 laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network: 55 cases of influenza A and one case of influenza B (Figure 8a).In week 51, 56 laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network: 55 cases of influenza A and one case of influenza B (Table 4). To date, 16 cases were admitted to the ICU, of which 10 (63%) were 2 to 9 years of age (Figure 9a). Among cases admitted to the ICU with available data, 79% (11/14) were reported to have underlying conditions or comorbidities.

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 51, 73 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. Sixty cases (82%) were in adults over the age of 65. Seventy-one cases (97%) were influenza A (Figure 8b). To date this season, 230 cases have been reported; 227 (99%) with influenza A. The majority of cases (85%) were among adults ≥65 years of age (Table 5). Eighteen ICU admissions have been reported and the majority of cases (77.8%) were adults ≥65 years of age with underlying conditions or comorbidities. Eight deaths have been reported, all adults >65 years of age (Figure 9b).

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

Figure 8A Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2015-16 - Text Description

Figure 8 A) Paediatric hospitalizations (≤16 years of age, IMPACT)

Report week	Influenza A	Influenza B
35	0	0
36	0	0
37	2	0
38	1	0
39	1	0
40	1	0
41	2	0
42	1	0
43	3	2
44	4	0
45	4	0
46	11	3
47	8	1
48	19	5
49	30	2
50	44	2
51	55	1

Figure 8B Number of cases of influenza reported by sentinel hospital networks, by week, Canada, 2015-16 - Text Description

Figure 8 B) Hospitalisations d'adultes (≥16 ans, PCIRN-SOS)

Semaine de déclaration	Influenza A	Influenza B	Influenza de type inconnu
35	n/a	n/a	n/a
36	n/a	n/a	n/a
37	n/a	n/a	n/a
38	n/a	n/a	n/a
39	n/a	n/a	n/a
40	n/a	n/a	n/a
41	n/a	n/a	n/a
42	n/a	n/a	n/a
43	n/a	n/a	n/a
44	n/a	n/a	n/a
45	n/a	n/a	n/a
46	3	0	0
47	8	0	0
48	32	0	0
49	39	0	0
50	77	3	0
51	71	0	2

Figure 9A Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada, 2014-15 A) Paediatric hospitalizations (≤16 years of age, IMPACT) - Text Description

Figure 9 A) Paediatric hospitalizations (≤16 years of age, IMPACT)

Age-group (years)	Hospitalizations (n=139)	ICU admissions (n=12)
0-5m	10.8%	0.0%
6-23m	20.2%	12.5%
2-4y	25.1%	25.0%
5-9y	28.1%	37.5%
10-16y	15.8%	25.0%

Figure 9B Percentage of hospitalizations, ICU admissions and deaths with influenza reported by age-group, Canada, 2014-15 B) Adult hospitalizations (≥16 year of age, PCIRN-SOS) - Text Description

Figure 9 B) Adult hospitalizations (≥16 year of age, PCIRN-SOS)

Age-group (years)	Hospitalizations (n=235)	ICU admissions(n=18)	Deaths (n=8)
16-20	0.9%	0.0%	0.0%
20-44	5.5%	11.1%	0.0%
45-64	8.5%	11.1%	0.0%
65+	85.1%	77.8%	100%

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 51, 187 laboratory-confirmed influenza-associated hospitalizations were reported from participating provinces and territories^{Footnote *}; all but three with influenza A, and 63% were patients ≥65 years of age. Since the start of the 2014-15 season, 782 hospitalizations have been reported; 762 (97%) with influenza A. Among cases for which the subtype of influenza A was reported, 99% (536/538) were A(H3N2). The majority of cases (60%) were ≥65 years of age (Table 6). Seventeen ICU admissions have been reported in adults ≥65 years of age with influenza A. Forty deaths with influenza A have been reported: one child <5 years of age, one adult 45-64 years and 38 adults ≥65 years of age. Detailed clinical information (e.g. underlying medical conditions) is not known for these cases.

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): Since the last FluWatch report, one new laboratory-confirmed case of human infection with avian influenza A(H7N9) virus have been reported by the World Health Organization. Globally to December 31, 2014, the WHO has been informed of a total of 470 laboratory-confirmed human cases with avian influenza A(H7N9) virus, including 182 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:

PHAC - Avian influenza A(H7N9)
WHO - Avian Influenza A(H7N9)

Influenza A(H5N6): One new laboratory-confirmed case of human infection with avian influenza A (H5N6) virus from China has been reported by the World Health Organization. The case was an adult under 65 years of age with history of exposure to live poultry trade market. No sustained human to human transmission was reported. Globally to December 31, 2014, Avian influenza A (H5N6) was only found in poultry, except once when this sub-type of virus was detected in one case from China that died of severe pneumonia in April 2014.

Middle East Respiratory Syndrome Coronavirus (MERS-CoV)

Since the last FluWatch report, three laboratory-confirmed cases and one death of MERS-CoV have been reported by the World Health Organization. Globally, from September 2012 to December 31, 2014, the WHO has been informed of a total of 941 laboratory-confirmed cases of infection with MERS-CoV, including 347 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:

• PHAC - Middle East respiratory syndrome coronavirus (MERS-CoV)
• WHO - Coronavirus infections

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. To date, there have been 11 commercial infected premises and one non-commercial infected premise. As part of regular investigation activities, CFIA is fully tracing movements in and out of these sites. This may lead to further premises being identified and depopulated, which would not be unexpected. While there are no reports of H5N2 related illness in humans, as a precautionary measure public health officials are monitoring workers who are exposed to affected poultry. Avian influenza viruses do not pose risks to food safety when poultry and poultry products are properly handled and cooked. Avian influenza rarely affects humans that do not have consistent contact with infected birds. Further information on the outbreak is provided on the following CFIA website.

• CFIA - Notifiable Avian Influenza

Enterovirus D68 (EV-D68)

Information related to enterovirus D68, as well as guidance for health professionals and advice for the public is updated regularly:

• Non-polio enterovirus infections

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

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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.

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 ILI^{Footnote *} 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 region^{Footnote †}

4 = Widespread:

1. evidence of increased ILI^{Footnote *} 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 region^{Footnote †}

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.