Overall influenza activity in Canada increased from the previous week
During week 12, overall influenza activity in Canada increased slightly with some indicators (laboratory detections, number of regions reporting widespread and localized activity and the number of outbreaks) having increased from the previous week. Widespread influenza activity was reported by 4 regions (in BC, AB, ON and QC) and localized influenza activity by 16 regions (in BC, AB, SK, ON, QC, NB & NS). Five regions reported no activity and 29 reported sporadic activity (see map). In week 12, the percentage of specimens that tested positive for influenza was 19% (881/4,740) for Canada as a whole; and regionally ranging from 51% in NS to 7% in AB (see table). This week, the ILI consultation rate was 24 ILI consultations per 1,000 patient visits (see ILI graph), which is within the expected range for this week. The sentinel response rate was 49%. Thirty-nine new outbreaks of influenza or ILI were reported this week as follows: 24 LTCFs, 6 others, 3 hospitals and 6 schools.

Antigenic Characterization:
The National Microbiology Laboratory (NML) has characterized 848 influenza viruses for the 2007-2008 influenza season: 402 (47%) A(H1N1), 92 (11%) A(H3N2) and 354 (42%) B viruses. Of the 402 influenza A(H1N1) viruses characterized, 388 (97%) were antigenically similar to A/Solomon Islands/3/2006 and 14 (3%) were antigenically similar to A/Brisbane/59/2007. Of the 92 influenza A(H3N2) viruses characterized, 5 (5%) were antigenically similar to A/Wisconsin/67/2005 and 87 (95%) were antigenically similar to A/Brisbane/10/2007. One of the 5 A/Wisconsin-like viruses had reduced titer to A/Wisconsin/67/2005 reference antiserum. Of the 354 influenza B isolates characterized, 4 (1%) were antigenically similar to B/Malaysia/2506/2004 and 350 (99%) 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 2008-2009 season (northern hemisphere) contain the following: an A/Brisbane/59/2007 (H1N1)-like virus; an A/Brisbane/10/2007 (H3N2)-like virus; and a B/Florida/4/2006-like virus.

• WHO

 

Antiviral Resistance:
Since the start of the season, the NML has tested 607 influenza A isolates (447 H1N1 and 160 H3N2) for amantadine resistance and found that 158 (99%) of the 160 H3N2 isolates were resistant to amantadine and 5 (1.1%) of 447 H1N1 isolates were resistant (see recommendation from the 2006-2007 influenza season below).

The NML has also tested 812 influenza isolates (407 A/H1N1, 87 A/H3N2 & 318 B) for oseltamivir (Tamiflu) resistance and found that 74 (18.2%) of the 407 H1N1 isolates tested were resistant to oseltamivir. The resistant isolates were from NL, NS, NB, QC, ON, MB, AB and BC. These oseltamivir resistant strains remain sensitive to the antiviral amantadine.

Influenza-associated Paediatric Hospitalizations:
In week 12, there were 13 new laboratory-confirmed influenza-associated paediatric hospitalizations reported through the Immunization Monitoring Program Active (IMPACT) network from BC, ON, QC and NL of which 7 (54%) were due to influenza A. Of the 314 hospitalizations reported so far this season, 63% (198/314) have been due to influenza A. The proportion of cases to date by age group are as follows: 20% were 0-5 month olds; 27% were 6-23 month olds; 23% were 2-4 year-olds; 21% were 5-9 year-olds; and 10% were 10-16 year-olds. Since the start of the season, 1 influenza-associated pediatric death has been reported to PHAC.

International:

WHO: During weeks 10–11, the level of overall influenza activity in the world slightly decreased. The majority of countries in the Northern Europe and United States of America reported drop of influenza activity. Significant increase of influenza activity was observed in Hong Kong SAR China.

• WHO

CDC: During week 11, influenza activity continued to decrease in the United States. Since September 30, 2007, CDC antigenically characterized 489 influenza viruses: 255 influenza A(H1) (175 A/Solomon Islands/3/2006-like, 19 showed somewhat reduced titers with antisera produced against A/Solomon Islands, and 61 were A/Brisbane/59/2007-like), 107 influenza A(H3) (20 A/Wisconsin/67/2005-like, 80 A/Brisbane/10/2007-like and 7 showed somewhat reduced titers with antisera produced against A/Wisconsin and A/Brisbane), and 127 influenza B viruses (7 belonging to the B/Victoria and 120 B/Yamagata lineage). Small numbers of influenza viruses resistant to oseltamivir have been detected in the United States, representing 6.7% (59/887) of all influenza viruses tested (9.1% among H1N1 viruses tested). To date, CDC has received a total of 48 reports of influenza-associated pediatric deaths that occurred this season.

• CDC

 

EISS: Most countries in Europe are now reporting a low intensity of influenza activity. Influenza virus type B accounted for 71% of the total positive specimens collected in week 12/2008, however the majority of virus detections since the start of the season have been influenza A(H1N1) viruses. Influenza A(H1N1) viruses resistant to oseltamivir have been found in 19 countries in Europe with an overall prevalence of 23% (507/2216).

• 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.

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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: March 16 to March 22, 2008				Season to Date: August 26, 2007 to March 22, 2008
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	68	1	12	13	875	49	104	153
PE	9	0	2	2	99	1	5	6
NS	61	16	15	31	543	34	35	69
NB	110	19	16	35	747	78	60	138
QC	1515	159	94	253	20018	1613	439	2052
ON	1468	208	133	341	23530	1433	491	1924
MB	87	3	5	8	2253	71	27	98
SK	219	26	31	57	4690	290	229	519
AB	1061	46	31	77	23406	739	836	1575
BC	142	26	38	64	2853	480	377	857
Canada	4740	504	377	881	79014	4788	2603	7391

 

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, March 16 to March 22, 2008 (Week 12)
	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=848]

{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