Influenza activity in Canada starting to decline; however influenza B detections still increasing
During week 11, overall influenza activity in Canada started to decline with some indicators (laboratory detections, number of regions reporting widespread and localized activity and the ILI consultation rate) having decreased slightly from the previous week. Widespread influenza activity was reported by 5 regions (in BC, AB & ON and QC) and localized influenza activity by 11 regions (in BC, SK, MB, ON, QC & NS). Four regions reported no activity and 36 reported sporadic activity (see map). In week 11, the percentage of specimens that tested positive for influenza declined slightly to 16% (796/4,972) for Canada as a whole; and regionally ranging from 38% in BC to 0% in PEI. Overall, the proportion of influenza B detections in Canada continued to increase steadily; however the proportion of influenza A virus detections in Canada declined from 10.6% in week 10 to 8.5% in week 11 (see table). This week, the ILI consultation rate was 27 ILI consultations per 1,000 patient visits (see ILI graph), which is within the expected range for this week. The sentinel response rate was 54%. Twenty-six new outbreaks of influenza or ILI were reported this week as follows: 20 LTCFs and 6 others.

Antigenic Characterization:
The National Microbiology Laboratory (NML) has characterized 746 influenza viruses for the 2007-2008 influenza season: 377 (50%) A(H1N1), 72 (10%) A(H3N2) and 297 (40%) B viruses. Of the 377 influenza A(H1N1) viruses characterized, 365 (97%) were antigenically similar to A/Solomon Islands/3/2006 and 12 (3%) were antigenically similar to A/Brisbane/59/2007. Of the 72 influenza A(H3N2) viruses characterized, 5 (7%) were antigenically similar to A/Wisconsin/67/2005 and 67 (93%) 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 297 influenza B isolates characterized, 3 (1%) were antigenically similar to B/Malaysia/2506/2004 and 294 (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. <http://www.who.int/csr/disease/influenza/recommendations2008_9north/en/index.html>

• WHO

 

Antiviral Resistance:
Since the start of the season, the NML has tested 550 influenza A isolates (410 H1N1 and 140 H3N2) for amantadine resistance and found that 138 (98%) of the 140 H3N2 isolates were resistant to amantadine and 5 (1.2%) of 410 H1N1 isolates were resistant (see recommendation from the 2006-2007 influenza season below).

The NML has also tested 689 influenza isolates (370 A/H1N1, 71 A/H3N2 & 248 B) for oseltamivir (Tamiflu) resistance and found that 57 (15.4%) of the 370 H1N1 isolates tested were resistant to oseltamivir. The resistant isolates were from NL, QC, ON, MB, AB and BC. These oseltamivir resistant strains remain sensitive to the antiviral amantadine.

Influenza-associated Paediatric Hospitalizations:
In week 11, there were 23 new laboratory-confirmed influenza-associated paediatric hospitalizations reported through the Immunization Monitoring Program Active (IMPACT) network from BC, AB, SK, ON, QC and NS of which 16 (70%) were due to influenza B. Of the 300 hospitalizations reported so far this season, 63% (188/300) have been due to influenza A. The proportion of cases to date by age group are as follows: 22% were 0-5 month olds; 26% were 6-23 month olds; 23% were 2-4 year-olds; 21% were 5-9 year-olds; and 9% were 10-16 year-olds. Since the start of the season, 1 influenza B-associated pediatric death has been reported (however not through the IMPACT network) and occurred in week 47 in BC. The child was recently immigrated and had underlying medical conditions.

International:

CDC: During week 10, influenza activity continued to decrease in the United States with the majority of influenza indicators having decreased from the previous week. Since September 30, 2007, CDC antigenically characterized 425 influenza viruses: 191 influenza A(H1) (147 A/Solomon Islands/3/2006-like, 19 showed somewhat reduced titers with antisera produced against A/Solomon Islands, and 25 were A/Brisbane/59/2007-like), 107 influenza A(H3) (20 A/Wisconsin/67/2005-like and 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 6.4% (51/793) of all influenza viruses tested (9.1% among H1N1 viruses tested). To date, CDC has received a total of 41 reports of influenza-associated pediatric deaths that occurred this season.

• CDC

 

Human Avian Influenza: Since 15 March 2008, the WHO reported 1 additional fatal case of H5N1 avian influenza infection from Viet Nam.

• 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: March 9 to March 15, 2008				Season to Date: August 26, 2007 to March 15, 2008
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	84	0	15	15	807	48	92	140
PE	9	0	0	0	90	1	3	4
NS	45	9	3	12	482	18	20	38
NB	52	8	2	10	637	59	44	103
QC	1672	216	94	310	18503	1454	345	1799
ON	1318	101	114	215	22062	1225	358	1583
MB	83	7	2	9	2166	68	22	90
SK	317	27	39	66	4471	264	198	462
AB	1210	37	52	89	22345	693	805	1498
BC	182	16	54	70	2711	454	339	793
Canada	4972	421	375	796	74274	4284	2226	6510

 

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 9 to March 15, 2008 (Week 11)
	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=746]

{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.

Single Maps | Dual Maps | Animated Maps | FluWatch Reports

Definitions for the 2007-2008 season