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Influenza activity increasing in the West; low levels of influenza activity in the rest of Canada

During week 47, localized influenza activity was reported in regions of British Columbia, Alberta and Ontario. Sporadic influenza activity was reported in regions of Alberta, Saskatchewan and Ontario while the rest of the country reported no activity (see map). In week 47, 29 (1.8%) of the 1,655 specimens tested for influenza virus were positive and all were influenza A (see table). The majority of influenza detections to date this season were influenza A viruses. The ILI consultation rate declined from the previous week to a rate of 12 per 1,000 patient visits in week 47, which is below the expected range for this week (see ILI graph) with a sentinel response rate of 66%. Note that fluctuations in the ILI consultation rate is affected by the rate of response by sentinels each week. During week 47, 5 new outbreaks if ILI were reported in schools in Alberta and British Columbia.

Respiratory Syncytial Virus (RSV), which is the most common cause of lower respiratory tract illness in young children, is one of the respiratory viruses causing ILI in the community. Note that over the last several weeks, the percent positive for RSV detections has increased significantly from 4.8% in week 44 to 17.4% in week 47.

Antigenic Characterization:
The National Microbiology Laboratory (NML) has characterized 10 influenza viruses for the 2006-2007 influenza season: 2 A/Wisconsin/67/2005(H3N2)-like viruses (from Ontario and Alberta) and 8 A/New Caledonia/20/99(H1N1)-like viruses (all from Alberta) (see pie chart). Both strains are included in the composition of the 2006-2007 Canadian influenza vaccine.

Antiviral Resistance:
The NML has tested 9 influenza A isolates for amantadine resistance this season and found that 2 influenza A/H3N2 isolates tested were resistant to amantadine. The other 7 isolates were influenza A/H1N1 which remain sensitive to amantadine. (see recommendation below)

Influenza-associated Pediatric Hospitalizations:
During week 47, one new laboratory-confirmed influenza-associated paediatric hospitalization from Alberta was reported through the Immunization Monitoring Program Active (IMPACT) network. This is the second case that has been reported to IMPACT since the start of this influenza season.

International:
CDC: During week 46, a low level of influenza activity was reported in the United States. The proportion of patient visits to sentinel providers for ILI and the proportion of deaths attributed to pneumonia and influenza were below baseline levels. Of the 2,135 specimens tested for influenza virus in week 46, 68 (3.2%) were positive. Since 1 October 2006, CDC has antigenically characterized 22 influenza viruses: 6 influenza A/New Caledonia/20/1999(H1N1)-like and 16 influenza B viruses (5 belonging to the B/Victoria lineage and 11 belonging to the B/Yamagata lineage). It is too early in the influenza season to determine which viruses will predominate or how well the vaccine and circulating strains will match.

• CDC

Recommendation for the Use of Amantadine for Treatment and Prevention of Influenza
The Public Health Agency of Canada does not recommend the use of amantadine for treatment or prevention of influenza for the 2006-2007 season. This recommendation will be revisited if new information becomes available.

Total number of influenza tests performed and number of positive tests by province/territory of testing laboratory, Canada, 2006-2007

Specimens from NT, YT, and NU are sent to reference laboratories in other provinces.

Note: Cumulative data includes updates to previous weeks; due to reporting delays, the sum of weekly report totals do not add up to cumulative totals.

Abbreviations: Newfoundland/Labrador (NL), Prince Edward Island (PE), New Brunswick (NB), Nova Scotia (NS), Quebec (QC), Ontario (ON), Manitoba (MB), Saskatchewan (SK), Alberta (AB), British Columbia (BC), Yukon (YT), Northwest Territories (NT), Nunavut (NU)

Respiratory virus laboratory detections in Canada, by geographic regions, are available weekly on the following website:
<http://www.phac-aspc.gc.ca/bid-bmi/dsd-dsm/rvdi-divr/index.html>

Number of influenza surveillance regions† reporting widespread or localized influenza activity, Canada, by report week, 2006-2007 (N=76)

† sub-regions within the province or territory as defined by the provincial/territorial epidemiologist. Graph may change as late returns come in.

Influenza Activity Level by Provincial and Territorial Influenza Surveillance Regions, Canada, November 19, 2006 to November 25, 2006 (Week 47)
	No Data No Activity Sporadic Activity Localized Activity Widespread Activity
Note: Influenza activity levels, as represented on this map, are assigned and reported by Provincial and Territorial Ministries of Health, based on laboratory confirmations, sentinel ILI rates (see graphs and tables) and outbreaks. Please refer to detailed definitions. For areas where no data is reported, late reports from these provinces and territories will appear on the FluWatch website. Select single maps by report week to get this updated information. <http://dsol-smed.phac-aspc.gc.ca/dsol-smed/fluwatch/fluwatch.phtml?lang=e> Click on the map to view provinces/territories and maps for other weeks.

Influenza tests reported and percentage of tests positive, Canada, by report week, 2006-2007

Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2006-2007

Influenza strain characterization, Canada, cumulative, 2006-2007 influenza season by the Respiratory Viruses Section at the National Microbiology Laboratory
[N=10]

{Strain characterization, number identified, per cent of total number}

NACI recommends that the trivalent vaccine for the 2006-2007 season in Canada contain A/New Caledonia/20/1999 (H1N1)-like, A/Wisconsin/67/2005 (H3N2)-like, and B/Malaysia/2506/2004-like virus antigens.

Influenza-like illness (ILI) consultation rates, Canada, by report week, 2006-2007 compared to 1996/97 through to 2005/06 seasons

Note: No data available for mean rate in previous years for weeks 19 to 39 (1996-1997 through 2002-2003 seasons).

Number of New Outbreaks in Long Term Care Facilities, Canada, by Report Week, 2006-2007

Please note that the above graphs may change as late returns come in.

Definitions for the 2006-2007 season

[FluWatch]