FluWatch report: November 16 to November 22, 2014 (Week 47)

Influenza and Other Respiratory Virus Detections

The number of positive influenza tests increased sharply to 295 influenza detections (8.6% of tests) in week 47, predominantly due to influenza A (Figure 2). To date, 97% of influenza detections have been influenza A, and the vast majority 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. To date, among the cases of influenza A with reported age, the largest proportion was in adults ≥65 years of age (47%) (Table 2).

In week 47, detections of RSV and adenovirus continued to follow an upward trend, in keeping with their usual pattern of seasonal circulation. Detections of rhinovirus peaked in week 39 and continue to follow a downward trend (figure 3).

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

Influenza Strain Characterizations

During the 2014-2015 influenza season, the National Microbiology Laboratory (NML) has characterized 22 influenza viruses [10 A(H3N2) and 12 influenza B]. Two influenza A viruses were antigenically similar to A/Texas/50/2012, and nine influenza B viruses were antigenically similar to the B/Massachusetts/2/2012 (Yamagata lineage) recommended by the WHO for the 2014-15 seasonal influenza vaccine. Eight influenza A(H3N2) viruses and three influenza B viruses showed reduced titers to antisera produced against strains recommended for the seasonal influenza vaccine (Figure 4).

Antiviral Resistance

During the 2014-2015 influenza season, NML has tested 37 influenza viruses for resistance to oseltamivir and zanamivir and all were sensitive to both agents. The 46 influenza A(H3N2) viruses tested for amantadine resistance were all resistant (Table 3).

Influenza-like Illness (ILI) Consultation Rate

The national influenza-like-illness (ILI) consultation rate decreased in week 47 to 26.8 consultations per 1,000 (Figure 5). To date this season, the rates have been highest among those <20 years of age.

Influenza Outbreak Surveillance

In week 47, 16 new outbreaks of influenza A were reported in long-term care facilities (LTCF) (Figure 6). Two additional outbreaks of influenza A were reported, one in a school and one in another setting. To date, 35 outbreaks in LTCF have been reported.

Pharmacy surveillance

During week 47, the proportion of prescriptions for antivirals increased to 23.7 antiviral prescriptions per 100,000 total prescriptions, which is in keeping with previous seasons and consistent with other indicators of influenza circulation (Figure 7).

Sentinel Hospital Influenza Surveillance

Paediatric Influenza Hospitalizations and Deaths (IMPACT)

In week 47, nine new laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network: 8 cases of influenza A and one case of influenza B (Figure 8a).To date this season, 38 hospitalizations have been reported by the IMPACT network, 34 (90%) of which were cases of influenza A, of these 71% were A(H3N2). The majority of cases (55%) were in children <5 years of age (Table 4). To date, five cases were admitted to the ICU (Figure 9a).

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)

Surveillance of laboratory-confirmed influenza-associated adult (≥16 years of age) hospitalizations by the PHAC/CIHR Influenza Research Network (PCIRN) Serious Outcomes Surveillance (SOS) network for the 2014-15 season began on November 15th, 2014. To date, nine cases have been reported, all adults ≥65 years of age with influenza A (Table 5). Two cases were admitted to the ICU (Figure 8b).

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.

Provincial/Territorial Influenza Hospitalizations and Deaths

In week 47, 22 laboratory-confirmed influenza-associated hospitalizations were reported from participating provinces and territories^{Footnote *}. Since the start of the 2014-15 season, 145 hospitalizations have been reported; 137 (95%) with influenza A, of which 83% were A(H3N2); 51% were patients ≥65 years of age (Table 6). Three ICU admissions have been reported in adults ≥45 years of age with influenza A. Eleven deaths with influenza A have been reported: one child <5 years of age, one adult 45-64 years and nine 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, no new laboratory-confirmed cases of human infection with avian influenza A(H7N9) virus have been reported by the World Health Organization. Globally to November 27, 2014, the WHO has been informed of a total of 458 laboratory-confirmed human cases with avian influenza A(H7N9) virus, including 177 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)

Middle East Respiratory Syndrome Coronavirus (MERS-CoV)

Globally, from September 2012 to November 27, 2014, the WHO has been informed of a total of 909 laboratory-confirmed cases of infection with MERS-CoV, including 331 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

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

FluWatch definitions for the 2014-2015 season

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.