Low influenza activity levels overall in Canada; elevated influenza activity continues in Alberta and Ontario

During week 52, influenza activity in Canada overall appears to have declined slightly from previous weeks based on a number of indicators. The number of regions reporting localized or widespread activity has declined to 2 from 4 in the previous week. The number of reports of sporadic influenza activity increased in week 52 (see map), however 6 of the 13 P/Ts have reported "no activity" in all of their regions to date this season. Note that no data for Saskatchewan and the Northwest Territories were received this week. In week 52, 5% (136/2765) of the specimens tested for influenza virus were positive (see table), a slight decline from 6% in week 51 and 7% in week 50. Of the influenza virus detections to date this season, 99% (667/676) were influenza A viruses. The ILI consultation rate declined from 25 per 1,000 patient visits in week 51 to 22 per 1,000 this week, which is below the expected range for this week (see ILI graph). Note that the sentinel response rate was low over the holidays (37%). During week 52, 2 new outbreaks were reported in Ontario (1 in a LTCF).
Week 51 update: Influenza activity in Alberta and British Columbia
The first report of widespread influenza activity this season in Canada was reported in week 51 in Southern Alberta. Localized activity was reported in the Central region and sporadic in the Northern region of the province. Four of the 5 regions in British Columbia reported sporadic influenza activity. In week 51, 11 new outbreaks of ILI were reported in schools in Alberta.
Respiratory Syncytial Virus (RSV): Over the last several months, the percent positive for RSV detections increased significantly from 7.8% in week 44 (early November) to 30% in week 52. The majority of the RSV detections were from Quebec, Ontario and the Prairies.

Antigenic Characterization:
The National Microbiology Laboratory (NML) has characterized 84 influenza viruses for the 2006-2007 influenza season: 30 were A/Wisconsin/67/05(H3N2)-like, 51 were A/New Caledonia/20/1999(H1N1)-like, 2 B/Malaysia/2506/2004-like, and 1 B/Shanghai/361/2002-like (see pie chart). All but the B/Shanghai/361/2002-like strain are included in the composition of the 2006-2007 Canadian influenza vaccine. Of the influenza A viruses characterized, 96% (49/51) of the A(H1N1) viruses were from the West and 97% (29/30) of the A(H3N2) viruses were from Ontario.

Antiviral Resistance:
Since the start of the season, the NML has tested 64 influenza A isolates (36 H1N1, 28 H3N2) for amantadine resistance. None of the H1N1 isolates tested were resistant to amantadine; however, 17% (4/24) of the H3N2 isolates were resistant (see recommendation below). Of the 72 influenza A isolates tested for oseltamivir resistance, none were found to be resistant.

Influenza-associated Pediatric Hospitalizations:
This week, there were two new laboratory-confirmed influenza-associated paediatric hospitalizations in Alberta reported through the Immunization Monitoring Program Active (IMPACT) network, all due to influenza A. Of the 15 hospitalizations reported so far this season, 93% (14/15) have been due to influenza A.

International:
EISS: Increased influenza activity was reported in some northern parts of Europe between Christmas and New Year. In the rest of Europe, clinical influenza activity remains below baseline levels; however, rates should be interpreted cautiously as ILI and ARI consultation rates reported in all countries are affected by seasonal holidays. In contrast to Canada and the United States where the predominant sub-type is influenza A(H1N1), the predominant sub-type in Europe has been A(H3N2) [A/Wisconsin/67/2005(H3N2)-like viruses] so far this season.

• EISS

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

Province of reporting laboratories Report Period: December 24, 2006 to December 30, 2006 Season to Date: August 27, 2006 - December 30, 2006 Total # Influenza Tests # of Positive Tests Total # Influenza Tests # of Positive Tests Influenza A Influenza B Total Influenza A Influenza B Total NL 17 0 0 0 138 0 0 0 PE 1 0 0 0 21 0 0 0 NS 0 0 0 0 297 0 0 0 NB 26 0 0 0 326 0 0 0 QC 575 9 1 10 5639 17 3 20 ON 615 32 0 32 9617 140 4 144 MB 43 0 0 0 798 0 0 0 SK 165 5 0 5 2213 16 0 16 AB 1214 81 0 81 9360 461 1 462 BC 109 8 0 8 1258 33 1 34 Canada 2765 135 1 136 29667 667 9 676

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-eng.php>

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, December 24, 2006 to December 30, 2006 (Week 52)
	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=84]

{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.

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Definitions for the 2006-2007 season