FluWatch report: November 2 to November 8, 2014 (Week 45)

Influenza and Other Respiratory Virus Detections

The number of positive influenza tests increased sharply to 106 influenza detections (3.5% of tests) in week 45 (Figure 2). To date, 85% of influenza detections have been influenza A, and the vast majority of those subtyped have been A(H3) (Table 1). Cases of influenza B have been reported among younger age-groups, with 28% being children <5 years of age (Table 2).

In week 45, detections of RSV, parainfluenza 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. More detections of rhinovirus were reported this year compared to previous seasons (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 12 influenza viruses [four A(H3N2) and eight influenza B]. One influenza A was antigenically similar to A/Texas/50/2012, and four 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. Three influenza A(H3N2) viruses and one influenza B virus 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 16 influenza viruses for resistance to oseltamivir and zanamivir and all were sensitive to both agents. The 17 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 45 to 23.1 consultations per 1,000 (Figure 5). The rates were highest among those <20 years of age in week 45. The rates since mid-June have been above the expected range for this time of year.

Influenza Outbreak Surveillance

In week 45, two new outbreaks of influenza A(H3N2) were reported in long-term care facilities (Figure 6).

Pharmacy surveillance

During week 45, the proportion of prescriptions for antivirals was stable at 17.8 antiviral prescriptions per 100,000 total prescriptions, which is in keeping with previous seasons (Figure 7).

Sentinel Hospital Influenza Surveillance

Paediatric Influenza Hospitalizations and Deaths (IMPACT)

In week 45, four new laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network (Figure 8a). To date this season, 19 hospitalizations have been reported by the IMPACT network, 18 of which were cases of influenza A, and 13 of these were A(H3N2). The majority of the cases (58%) were in children <5 years of age (Table 4). To date, two 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 has not yet begun for the 2014-15 season (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.

Table 5 - Cumulative numbers of adult hospitalizations with influenza reported by the PCIRN-SOS network, Canada, 2014-15

Provincial/Territorial Influenza Hospitalizations and Deaths

Since the start of the 2014-15 season, 73 laboratory-confirmed influenza-associated hospitalizations have been reported from participating provinces and territories^{Footnote *}; 69 were cases of influenza A, of which the majority were A(H3N2); 55% were patients ≥65 years of age (Table 6). No ICU admissions were reported. Eight deaths with influenza A have been reported: one child <5 years of age and seven adults ≥45 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): Globally to November 13, 2014, the WHO has been informed of a total of 455 laboratory-confirmed human cases with avian influenza A(H7N9) virus, including 176 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 13, 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

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.