FluWatch report: October 5 to 11, 2014 (Week 41)

Influenza/ILI Activity (geographic spread)

In week 41, the majority of regions in Canada reported no activity; however, three regions (BC(1), ON(2)) reported localized activity and 13 regions (BC(2), AB(4), MB(1), ON(2) and QC(4)) reported sporadic activity (Figure 1).

Influenza and Other Respiratory Virus Detections

The number of positive influenza tests continued to increase in week 41 to 50 influenza detections (1.7% of tests) (Figure 2). To date, 86% of influenza detections have been influenza A, and the 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 (56%) (Table 2).

In week 41, detections of some respiratory viruses were at inter-seasonal levels (human metapneumovirus) or in keeping with their usual pattern of seasonal circulation (RSV, parainfluenza, and coronavirus). Detections of adenovirus were higher than in previous seasons. Detections of rhinovirus seem to have peaked in week 39 at a level higher than observed in previous seasons, but decreased over the past two weeks (figure 3).

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

Influenza Strain Characterizations

The National Microbiology Laboratory (NML) has not yet reported any influenza strain characterizations for the 2014-15 season (Figure 4).

Antiviral Resistance

During the 2014-2015 influenza season, NML has tested 2 influenza viruses for resistance to oseltamivir and zanamivir and both were sensitive to both agents. The one influenza A virus tested for amantadine resistance was resistant (Table 3).

Influenza-like Illness (ILI) Consultation Rate

The national influenza-like-illness (ILI) consultation rate continued to increase, and was 31.6 per 1,000 consultations in week 41 (Figure 5). The rates since mid-June have been above the expected range for this time of year.

Influenza Outbreak Surveillance

In week 41, one new outbreak of influenza B was reported in a long-term care facility (Figure 6).

Pharmacy surveillance

During week 41, the proportion of prescriptions for antivirals was approximately 11 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 41, two 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, seven hospitalizations have been reported by the IMPACT network, all cases of influenza A, and four of the seven were A(H3N2) (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, 25 laboratory-confirmed influenza-associated hospitalizations have been reported from participating provinces and territories^{Footnote *}, 24 were cases of influenza A, of which the majority were A(H3N2); 56% were patients ≥65 years of age. No ICU admissions were reported. Two 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 surveillance and/or 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): No new cases of human infection with influenza A(H7N9) have been reported by the World Health Organization since the last FluWatch report. Globally to October 16, 2014, the WHO has been informed of a total of 453 laboratory-confirmed human cases with avian influenza A(H7N9) virus, including 175 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 16, 2014, the WHO has been informed of a total of 877 laboratory-confirmed cases of infection with MERS-CoV, including 317 deaths. Since the last FluWatch report, 19 new cases have been identified during a retrospective review of hospital records. 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.