Influenza activity remains low in Canada, similar to previous weeks
During week 46, influenza activity levels remained low in Canada where most regions across the country reported no activity. The number of regions reporting sporadic influenza activity declined from 11 regions in week 45 to 9 regions in week 46. However, localized activity was reported in 2 new regions (in central Alberta and Toronto) (see map). In week 46, 3 (0.2%) of the 1,617 specimens tested were positive for influenza virus: 1 influenza A (from Ontario) and 2 influenza B (from Alberta). Of the influenza detections to date, 81% (22/27) were influenza A and 19% (5/27) were influenza B (see table). The ILI consultation rate remains low at 10 ILI consultations per 1,000 patient visits (see ILI graph) with a low sentinel response rate of 56% in week 46 (sentinel response rates are expected to increase as the season progresses). In week 46, one new influenza outbreak was reported in a LTCF in Alberta. Since the start of the season, 4 LTCF outbreaks have been reported (2 in Ontario and 2 in Alberta). In the current season to date, no new laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network.

Antigenic Characterization:
The National Microbiology Laboratory (NML) has characterized 7 influenza viruses for the 2007-2008 influenza season: 1 A(H1N1), 4 A(H3N2) and 2 B viruses. The influenza A/H1N1 virus was antigenically similar to A/Solomon Islands/3/2006 (which is the influenza A(H1N1) component recommended for the 2007-2008 influenza vaccine). Of the 4 influenza A(H3N2) viruses characterized, 3 were antigenically similar to A/Wisconsin/67/2005 (which is the influenza A(H3N2) component recommended for the 2007-2008 influenza vaccine) and 1 was antigenically similar to A/Brisbane/10/2007. One of the 3 A/Wisconsin-like viruses had reduced titer to A/Wisconsin/67/2005 reference antiserum. The 2 influenza B isolates characterized were antigenically similar to B/Florida/4/2006, belonging to the B/Yamagata lineage, and is the B component recommended for the 2008 influenza vaccine in the Southern Hemisphere (see pie chart).

Note: The results of the strain identifications indicate that there may be some degree of antigenic drift this season, however, the current Canadian vaccine is still expected to provide a level of protection against this new variant.

* The WHO recommends that the vaccines to be used in the 2007-2008 season (northern hemisphere) contain the following: an A/Solomon Islands/3/2006 (H1N1)-like virus; an A/Wisconsin/67/2005 (H3N2)-like virus; and a B/Malaysia/2506/2004-like (B/Victoria/2/1987 lineage) virus.

Antiviral Resistance:
Since the start of the season, the NML has tested 6 influenza A isolates (all H3N2) for amantadine resistance (from Ontario, Alberta and British Columbia). Four (67% or 4/6) of the isolates tested were resistant to amantadine (3 of which originated from Ontario and one from Alberta) (see recommendation from the 2006-2007 influenza season below). Of the 5 isolates tested for oseltamivir resistance (3 influenza A, 2 influenza B), none were found to be resistant.

WHO: During weeks 44-45, the level of overall influenza activity in the world remained low with sporadic activity observed in some countries.

• WHO

CDC: A low level of influenza activity was reported in the United States during week 45. The majority of influenza detections to date were for influenza A viruses (94%). Since September 30, 2007, CDC antigenically characterized 1 influenza isolate: an influenza B virus characterized as B/Florida/04/2006 belonging to the B/Yamagata/16/1988 lineage. Two influenza-associated pediatric deaths were reported during week 45; however, the deaths occurred during the 2006-2007 season. No deaths have been reported for the 2007-2008 season.

• CDC

EISS: Influenza activity in Europe remains low. There have been only sporadic laboratory confirmed cases of influenza since week 40/2007. Based on the antigenic and/or genetic characterisation of 14 influenza viruses, eight were A/Solomon Island/3/2006 (H1N1)-like and six were B/Florida/4/2006-like (B/Yamagata/16/88 lineage), however, it is too early to say which virus type or subtype will become dominant in Europe this season. Compared to previous seasons it is noteworthy that about 73% of all subtyped influenza A viruses are of the H1 subtype.

• 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, 2007-2008

Province of reporting laboratories	Report Period: November 11, 2007 to November 17, 2007				Season to Date: August 26, 2007 to November 17, 2007
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	10	0	0	0	47	0	0	0
PE	3	0	0	0	23	0	0	0
NS	8	0	0	0	118	0	1	1
NB	27	0	0	0	114	0	0	0
QC	277	0	0	0	2204	5	0	5
ON	426	1	0	1	3625	6	1	7
MB	88	0	0	0	474	0	0	0
SK	75	0	0	0	923	0	0	0
AB	658	0	2	2	5602	10	3	13
BC	45	0	0	0	372	1	0	1
Canada	1617	1	2	3	13502	22	5	27

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, 2007-2008 (N=54)

† 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, 11 November to 17 November, 2007 (Week 46)
	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, 2007-2008

Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2007-2008

Influenza strain characterization, Canada, cumulative, 2007-2008 influenza season by the Respiratory Viruses Section at the National Microbiology Laboratory
[N=7]

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

NACI recommends that the trivalent vaccine for the 2007-2008 season in Canada contain A/Solomon Islands/3/2006 (H1N1)-like virus; an A/Wisconsin/67/2005 (H3N2)-like virus; and a B/Malaysia/2506/2004-like virus.

Influenza-like illness (ILI) consultation rates, Canada, by report week, 2007-2008 compared to 1996/97 through to 2006/07 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, 2007-2008

 

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

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Definitions for the 2007-2008 season