FluWatch report: September 13 to September 26, 2015 (weeks 37 and 38)

Laboratory Confirmed Influenza Detections

Although the number of positive influenza tests increased over the two week period, the percent positive for influenza detections remains low (1.5%) (Figure 2).

Most jurisdictions have reported only sporadic numbers of influenza detections in recent weeks. The majority of detections in Canada have been reported from BC, accounting for 77% of influenza detections in Canada in week 38. To date, 94% of influenza detections have been influenza A and the majority of those subtyped have been A(H3).

Among cases with reported age, the largest proportion was in those ≥65 years of age (52%) (Table 1).

For additional data on other respiratory virus detections see the Respiratory Virus Detections in Canada Report on the Public Health Agency of Canada website.

Influenza-like Illness Consultation Rate

The national influenza-like-illness (ILI) consultation rate increased from 13.2 consultations per 1,000 patient visits in week 37 to 14.8 per 1,000 visits in week 38. In week 38, the highest ILI consultation rate was found in the 5-19 age group and the lowest was found in the ≥65 age group (Figure 4).

Influenza Outbreak Surveillance

In week 37, two new outbreaks of influenza were reported. One influenza A(H3) outbreak was reported in a long-term care facility (LTCF) and the other of unknown type was reported in an institutional or community setting (Figure 5). No outbreaks were reported in week 38.

Sentinel Pediatric Hospital Influenza Surveillance

Paediatric Influenza Hospitalizations and Deaths (IMPACT)

To date, less than five laboratory-confirmed influenza-associated paediatric (≤16 years of age) hospitalizations have been reported by the Immunization Monitoring Program Active (IMPACT) network. The hospitalized cases were due to influenza A.

Provincial/Territorial Influenza Hospitalizations and Deaths

Since the start of the 2015-16 season, nine laboratory-confirmed influenza-associated hospitalizations were reported from participating provinces and territories^{Footnote *}. All were due to influenza A and the majority were patients ≥65 years of age. Two ICU admissions have also been reported.

See additional data on Reported Influenza Hospitalizations and Deaths in Canada: 2011-12 to 2015-16 on the Public Health Agency of Canada website.

Influenza Strain Characterizations

The National Microbiology Laboratory (NML) has not yet reported any influenza strain characterizations for the 2015-16 season (Figure 9).

Antiviral Resistance

The NML has not yet reported antivirual resistance results for influenza viruses collected during the 2015-16 season (Table 2).

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 2015-2016 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.