Overall influenza activity in Canada remains low
During week 52, influenza activity levels in Canada remained fairly low; however, several provinces (PEI and AB) and a few regions (in ON) did not report activity levels this week. Only two influenza surveillance regions (in ON and SK) reported localized influenza activity, while the rest reported either no activity (n=31) or sporadic activity (n=17) (see map). In week 52, 7.1% (90/1,257) of the specimens tested were positive for influenza. (Note: no laboratory data were obtained from QC this week). The majority of influenza detections this week were for influenza A viruses (78%). Of the influenza detections to date, 78% were influenza A and 22% were influenza B (see table).This week, the ILI consultation rate rose to 30 ILI consultations per 1,000 patient visits (see ILI graph), which is within the expected range for this week. Note, however, that the sentinel response rate was very low at 34%. One new LTCF outbreak was reported in week 52 (from ON). In week 52, two new laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network (from Toronto). In addition, 10 paediatric hospitalizations were retrospectively reported, all from Toronto: four in week 51, five in week 50 and one in week 49. Since the start of the season, 12 paediatric hospitalizations have been reported through the IMPACT network.

Antigenic Characterization:
The National Microbiology Laboratory (NML) has characterized 48 influenza viruses for the 2007-2008 influenza season: 31 A(H1N1), 6 A(H3N2) and 11 B viruses. All influenza A(H1N1) viruses were antigenically similar to A/Solomon Islands/3/2006. Of the six influenza A(H3N2) viruses characterized, five were antigenically similar to A/Wisconsin/67/2005 and one 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 11 influenza B isolates characterized, two were antigenically similar to B/Malaysia/2506/2004 and nine 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 40 influenza A isolates (31 H1N1 and 9 H3N2) for amantadine resistance and found that seven (78%) of the nine H3N2 isolates were resistant to amantadine (originating from ON and AB) and one (3%) of 31 H1N1 isolates was resistant (originating from BC) (see recommendation from the 2006-2007 influenza season below). Of the 33 isolates tested for oseltamivir resistance (24 influenza A, 9 influenza B), none were found to be resistant.

International:

CDC: During week 51, influenza activity continued to increase in the United States. Three states reported regional influenza activity, six states reported local influenza activity and the majority reported sporadic (n=32) and no influenza activity (n=8). The proportion of specimens that tested positive for influenza virus was 3.7% this week. The majority of influenza detections to date were for influenza A viruses (89%). Since September 30, 2007, CDC antigenically characterized 66 influenza viruses: 32 influenza A(H1) (all A/Solomon Islands/3/2006), 19 influenza A(H3) (4 A/Wisconsin/67/2005-like and 14 A/Brisbane/10/2007-like, and one showed somewhat reduced titers with antisera produced against A/Wisconsin/67/2005 and A/Brisbane/10/2007), and 15 influenza B viruses (all belonging to the B/Yamagata/16/1988 lineage). To date this season, one influenza-associated pediatric death has been reported to the CDC (in week 48).

• CDC

EISS: During week 52, an increased level of influenza activity was reported in Spain and low levels were reported across the rest of Europe. Of the total virus detections since week 40/2007 (N=995), 81% were influenza A of which over 94% were of the H1 subtype. So far this season, the consultation rates for ILI and/or ARI have been at levels usually seen outside the seasonal influenza peak period in most countries in Europe. Based on the antigenic and/or genetic characterisation of 148 influenza viruses, 117 were A/Solomon Island/3/2006 (H1N1)-like, seven were A/Brisbane/10/2007 (H3N2)-like, 14 were B/Florida/4/2006-like and 10 were B/Malaysia/2506/2004-like.

• EISS

Human Avian Influenza: Since 29 December, the WHO reported two additional cases (both fatal) of H5N1 avian influenza infection in Egypt. The first case is a 25-year-old female who developed symptoms on 26 December, was hospitalized on 27 December and died on 30 December. The second case is a 36-year-old female who developed symptoms on 26 December, was hospitalized on 29 December and died on 31 December.

• 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.

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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 23, 2007 to December 29, 2007				Season to Date: August 26, 2007 to December 29, 2007
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	11	2	0	2	120	3	0	3
PE	0	0	0	0	28	0	0	0
NS	10	0	0	0	179	0	1	1
NB	19	0	0	0	206	0	0	0
QC	NA	NA	NA	0	4258	16	4	20
ON	399	38	0	38	7063	205	2	207
MB	24	0	0	0	659	0	0	0
SK	157	11	5	16	1680	21	10	31
AB	566	8	14	22	10372	31	68	99
BC	71	11	1	12	722	36	5	41
Canada	1257	70	20	90	25287	312	90	402

 

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, 23 December to 29 December, 2007 (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, 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=48]

{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