Influenza activity remains low in Canada
During week 44, influenza activity levels remained low in Canada where most regions across the country reported no activity. Sporadic influenza activity was reported in a few regions (in Nova Scotia, Quebec, Ontario and Alberta ) and localized activity was reported in the central east Ontario region (see map). In week 44, 2 (0.15%) of the 1,296 specimens tested were positive for influenza virus. Of the influenza detections to date, 89% (17/19) were influenza A and 11% (2/19) were influenza B (see table). The ILI consultation rate was similar to the previous week (7 ILI consultations per 1,000 patient visits) and is below the expected range (see ILI graph). Sentinel response rates over recent weeks have been low (56% in week 44) but are expected to increase as the season progresses. In week 44, no new influenza outbreaks were reported. Since the start of the season, 3 LTCF outbreaks have been reported (2 from Ontario and 1 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 6 influenza viruses for the 2007-2008 influenza season: 4 A(H3N2) and 2 B viruses. Of the 4 influenza A(H3N2) viruses characterized, 2 were antigenically similar to A/Wisconsin/67/2005 (which is the influenza A(H3N2) component recommended for the 2007-2008 influenza vaccine), 1 had reduced titer to the A/Wisconsin/67/2005, and 1 was antigenically similar to A/Brisbane/10/2007. 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 40-43, the level of overall influenza activity in the world remained low with sporadic activity observed in some countries. In countries reporting sporadic influenza activity, both influenza A (H1 and H3) and B were detected.

• WHO

CDC: A low level of influenza activity was reported in the United States during week 43 with only 2 states reporting localized activity. Of the 1,252 specimens tested for influenza virus, 33 (2.6%) were positive. Of the positive influenza detections to date, 93% (112/120) were influenza A and 7% (8/120) were influenza B. The proportion of deaths attributed to pneumonia and influenza was below the epidemic threshold, and the proportion of outpatient visits for ILI (1.3%) was below national and region-specific baseline levels. From May 20 - September 29, 2007, CDC antigenically characterized 14 influenza isolates: 2 influenza A (H1) (both A/Solomon Islands/3/2006(H1N1)-like); 10 influenza A (H3) (6 A/Wisconsin/67/2005(H3N2)-like, 2 A/Brisbane/10/2007(H3N2)-like and 2 showed reduced titers to A/Wisconsin/67/2005 and A/Brisbane/10/2007); and 2 B/Yamagata lineage viruses.

• CDC

EISS: In week 44, low levels of influenza activity in Europe were reported which is typical for this time of year. There have only been sporadic laboratory confirmed cases of influenza since week 40 (N=47) of which 64% were influenza A and 36% influenza B. So far this season, the consultation rates for ILI and/or ARI for Europe as a whole have been at levels usually seen outside the winter period. Based on antigenic and/or genetic characterization of 7 influenza viruses, 6 were A/Solomon Islands/3/2006(H1N1)-like and 1 was 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.

• EISS

Human Avian Influenza: Since 3 November 2007, the WHO reported one new case of human infection with the H5N1 avian influenza virus from Indonesia. The case was a 30-year-old female who developed symptoms on 23 October, was hospitalized on 31 October, and died in an avian influenza referral hospital on 3 November.

• WHO

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: October 28, 2007 to November 3, 2007				Season to Date: August 26, 2007 to November 3, 2007
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	0	0	0	0	25	0	0	0
PE	0	0	0	0	20	0	0	0
NS	10	0	0	0	95	0	1	1
NB	14	0	0	0	76	0	0	0
QC	198	1	0	1	1719	2	0	2
ON	354	0	0	0	2722	5	1	6
MB	39	0	0	0	357	0	0	0
SK	71	0	0	0	733	0	0	0
AB	577	1	0	1	4332	9	0	9
BC	33	0	0	0	262	1	0	1
Canada	1296	2	0	2	10341	17	2	19

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, 28 October to 3 November, 2007 (Week 44)
	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=6]

{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