Influenza activity increasing in certain regions; however, overall influenza activity in Canada remains low
During week 49, influenza activity levels remained low in Canada overall with the majority of influenza surveillance regions across the country still reporting no activity (n=48). Seventeen regions reported sporadic influenza activity and only 2 regions (in central Alberta and the Interior region of British Columbia) reported localized activity (see map). Note: No data was received from the Toronto region in Ontario this week. The proportion of positive influenza tests increased from 0.6% (10/1,789) in the previous week to 2.2% (48/2,135) in week 49. This week, the majority of influenza detections were for influenza A viruses (91.7% or 44/48) and the highest number of detections coming from Ontario (n=34 or 71%). Of the influenza detections to date, 85% (83/98) were influenza A and 15% (15/98) were influenza B (see table). The ILI consultation rate increased slightly from the previous week to 18 ILI consultations per 1,000 patient visits (see ILI graph) and is still within the expected rate for this week. The sentinel response rate was 64%. Two new outbreaks of ILI were reported in schools in Alberta and British Columbia this week. Since the start of the season, 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 33 influenza viruses for the 2007-2008 influenza season: 18 A(H1N1), 6 A(H3N2) and 9 B viruses. All influenza A(H1N1) viruses were antigenically similar to A/Solomon Islands/3/2006. Of the 6 influenza A(H3N2) viruses characterized, 5 were antigenically similar to A/Wisconsin/67/2005 and 1 was antigenically similar to A/Brisbane/10/2007. One of the five A/Wisconsin-like viruses had reduced titer to A/Wisconsin/67/2005 reference antiserum. Of the 9 influenza B isolates characterized, 2 were antigenically similar to B/Malaysia/2506/2004 and 7 were antigenically similar to B/Florida/4/2006 (belonging to the B/Yamagata lineage) (see pie chart).

* 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 15 influenza A isolates (7 H1N1 and 8 H3N2) for amantadine resistance (from Ontario, Alberta and British Columbia). Six (40% or 6/15) of the isolates tested were resistant to amantadine (originating from Ontario and Alberta), all of which were H3N2 viruses (see recommendation from the 2006-2007 influenza season below). Of the 30 isolates tested for oseltamivir resistance (22 influenza A, 8 influenza B), none were found to be resistant.

International:

CDC: A low level of influenza activity was reported in the United States during week 48 with only 4 states reporting local influenza activity and the majority reporting sporadic (n=33) and no influenza activity (n=13). Of the specimens tested for influenza virus, 3.4% were positive. The majority of influenza detections to date were for influenza A viruses (92%). Since September 30, 2007, CDC antigenically characterized 27 influenza viruses: 19 influenza A(H1) (all A/Solomon Islands/3/2006), 5 influenza A(H3) (2 A/Wisconsin/67/2005-like and 3 A/Brisbane/10/2007-like), and 3 influenza B viruses (all belonging to the B/Yamagata/16/1988 lineage). One influenza-associated pediatric death was reported from Texas in week 48 and is the first influenza-associated pediatric death reported during the current season.

• CDC

EISS: Influenza activity in Europe remained low, including the number of influenza virus detections. Of the influenza virus detections since week 40, 76% were influenza A of which about 90% were of the H1 subtype. Based on the antigenic and/or genetic characterisation of 68 influenza viruses, 59 were A/Solomon Island/3/2006 (H1N1)-like, 1 was A/Brisbane/10/2007-like, 6 were B/Florida/4/2006-like (B/Yamagata/16/88 lineage) and 2 were B/Malaysia/2506/2004-like (B/Victoria/2/1987 lineage).

• EISS

Human Avian Influenza: Since 8 December 2007, the WHO reported 4 new cases of human infection with the H5N1 avian influenza virus. The first case was a 52-year-old male, currently in hospital, from China who was the father of the 24-year-old man who died on 2 December. Two other cases (1 fatal) were from Indonesia. The 4th case was a 7-year-old female from Myanmar who developed symptoms on 21 November and was hospitalized on 27 November. This was the first reported human case of H5N1 infection in Myanmar. As expected based on previous years, avian influenza H5N1 outbreaks and therefore human avian influenza cases have been seen to increase during the winter months. Additional cases may be expected in the coming months.

• 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: December 2, 2007 to December 8, 2007				Season to Date: August 26, 2007 to December 8, 2007
	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	82	0	0	0
PE	NA	NA	NA	0	25	0	0	0
NS	8	0	0	0	148	0	1	1
NB	19	0	0	0	158	0	0	0
QC	379	2	0	2	3253	8	3	11
ON	517	34	0	34	5098	50	2	52
MB	40	0	0	0	553	0	0	0
SK	122	0	0	0	1207	0	0	0
AB	974	4	4	8	8132	17	8	25
BC	59	4	0	4	529	8	1	9
Canada	2135	44	4	48	19185	83	15	98

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, 2 November to 8 December, 2007 (Week 49)
	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=33]

{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