FluWatch report: October 19 to 25, 2014 (Week 43)

Influenza and Other Respiratory Virus Detections

The number of positive influenza tests continued to increase in week 43 to 66 influenza detections (2.1% of tests) (Figure 2). To date, 84% of influenza detections have been influenza A, and the vast majority of those subtyped have been A(H3) (Table 1). Among cases with reported age, the largest proportion was in those ≥65 years of age (46%). Children <5 years accounted for 16% of all cases (Table 2).

In week 43, detections of RSV, parainfluenza and adenovirus increased, in keeping with their usual pattern of seasonal circulation. Detections of rhinovirus peaked in week 39 and decreased over the following three weeks but increased in week 43. 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 antigenically characterized 2 influenza viruses [one A(H3N2) and one influenza B]. Both viruses were similar to the strains recommended by the WHO for the 2014-15 seasonal influenza vaccine (Figure 4).

Antiviral Resistance

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

Influenza-like Illness (ILI) Consultation Rate

The national influenza-like-illness (ILI) consultation rate increased in week 43 to 35.7 consultations per 1,000  (Figure 5). The rates were highest among those <20 years of age in week 43. The rates since mid-June have been above the expected range for this time of year.

Influenza Outbreak Surveillance

In week 43, two new outbreaks of influenza A were reported in long-term care facilities (Figure 6).

Pharmacy surveillance

During week 43, the proportion of prescriptions for antivirals increased to 16.9 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 43, three 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, 11 hospitalizations have been reported by the IMPACT network, 10 of which were cases of influenza A, and 7 of these 10 were A(H3N2). The majority of the cases (63%) 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, 43 laboratory-confirmed influenza-associated hospitalizations have been reported from participating provinces and territories^{Footnote *},  41 were cases of influenza A, of which the majority were A(H3N2); 53% were patients ≥65 years of age (Table 6). No ICU admissions were reported. Three deaths with influenza A(H3N2) have been reported in adults ≥45 years of age. There is a reporting delay from some regions that have not yet begun submission of weekly reports.

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 October 30, 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 October 30, 2014, the WHO has been informed of a total of 885 laboratory-confirmed cases of infection with MERS-CoV, including 319 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)

The Chief Public Health Officer of Canada released a message on EV-D68 on October 17, 2014 and can be viewed through the following link: Message from the Chief Public Health Officer of Canada - Enterovirus-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.