Influenza activity in Canada continues to increase gradually
During week 09, overall influenza activity in Canada increased slightly from previous weeks with all indicators of influenza activity having increased compared to week 08. Widespread influenza activity was reported by 5 regions (in BC & ON) and localized influenza activity by 17 regions (in AB, SK, MB, ON, QC, NB & NS). Nine regions reported no activity and 25 reported sporadic activity (see map). In week 09, the percentage of specimens that tested positive for influenza was 17% (852/5,033) for Canada as a whole; and regionally ranging from 48% in BC to 0% in PEI. The proportion of influenza B detections in Canada continued to increase, accounting for 38% of detections in week 09; however, the majority of influenza detections were still for influenza A viruses (see table). This week, the ILI consultation rate rose to 21 ILI consultations per 1,000 patient visits (see ILI graph), which is below the expected range for this week. The sentinel response rate was 57%. Forty-two new outbreaks of influenza or ILI were reported this week as follows: 17 LTCFs, 20 schools, 1 hospital and 4 others.

Antigenic Characterization:
The National Microbiology Laboratory (NML) has characterized 555 influenza viruses for the 2007-2008 influenza season: 309 (56%) A(H1N1), 43 (8%) A(H3N2) and 203 (37%) B viruses. All influenza A(H1N1) viruses were antigenically similar to A/Solomon Islands/3/2006. Of the 43 influenza A(H3N2) viruses characterized, 5 (12%) were antigenically similar to A/Wisconsin/67/2005 and 38 (88%) 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 203 influenza B isolates characterized, 3 (1%) were antigenically similar to B/Malaysia/2506/2004 and 200 (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 433 influenza A isolates (345 H1N1 and 88 H3N2) for amantadine resistance and found that 86 (98%) of the 88 H3N2 isolates were resistant to amantadine and 5 (1.4%) of 345 H1N1 isolates were resistant (see recommendation from the 2006-2007 influenza season below).
The NML has also tested 505 influenza isolates (283 A/H1N1, 46 A/H3N2 & 176 B) for oseltamivir (Tamiflu) resistance and found that 38 (13%) of the 283 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 09, there were 25 new laboratory-confirmed influenza-associated paediatric hospitalizations reported through the Immunization Monitoring Program Active (IMPACT) network from SK, ON and QC of which 15 (60%) were due to influenza A. Of the 185 hospitalizations reported so far this season, 73% (135/185) have been due to influenza A. The proportion of cases to date by age group are as follows: 25% were 0-5 month olds; 22% were 6-23 month olds; 23% were 2-4 year-olds; 20% were 5-9 year-olds; and 11% were 10-16 year-olds.
*** Due to technical difficulties with IMPACT's electronic reporting system, real-time reports of hospitalizations were not received since early December 2007. Over the next several weeks, more retrospective reports of cases are expected.

International:

WHO: During weeks 8–9, the level of overall influenza activity in the world remained unchanged in most countries of Northern Europe and North America, where most viruses were detected. The highest level of influenza activity in the Northern Hemisphere is expected for this time of the year. Influenza A (H1N1) viruses predominated, but the proportion of influenza B steadily increased in the last weeks. Influenza A (H3N2) circulated as well.

• WHO

CDC: During week 08, influenza activity decreased slightly in the United States with some indicators (i.e. laboratory detections and ILI) having decreased from the previous week. Since September 30, 2007, CDC antigenically characterized 303 influenza viruses: 157 influenza A(H1) (124 A/Solomon Islands/3/2006-like, 19 showed somewhat reduced titers with antisera produced against A/Solomon Islands, and 14 were A/Brisbane/59/2007-like), 77 influenza A(H3) (12 A/Wisconsin/67/2005-like and 61 A/Brisbane/10/2007-like, and 4 showed somewhat reduced titers with antisera produced against A/Wisconsin and A/Brisbane), and 69 influenza B viruses (4 belonging to the B/Victoria and 65 B/Yamagata lineage). Small numbers of influenza viruses resistant to oseltamivir have been detected in the United States, representing 6.8% (38/557) of all influenza viruses tested (9.6% among H1N1 viruses tested).

• CDC

EISS: In week 09, medium intensity of influenza activity was reported in 15 European countries however in most countries, influenza activity is declining or stable. The proportion of influenza B continues to increase representing 55% of detections in week 09. A number of recent A(H1N1) viruses showed a better antigenic match to A/Brisbane/59/2007(H1N1), the WHO recommended H1N1 virus strain for the 2008-2009 season.

• EISS

Human Avian Influenza: Since 1 March 2008, the WHO reported 2 additional cases (1 fatal) of H5N1 avian influenza infection from Egypt.

• 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: February 24 to March 1, 2008				Season to Date: August 26, 2007 to March 1, 2008
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	86	3	31	34	599	43	55	98
PE	6	0	0	0	71	0	3	3
NS	44	2	6	8	390	6	12	18
NB	71	13	8	21	518	30	29	59
QC	1680	260	57	317	15133	985	178	1163
ON	1396	88	35	123	19159	998	156	1154
MB	95	13	2	15	1949	42	14	56
SK	358	50	28	78	3787	214	130	344
AB	1053	62	77	139	20102	595	685	1280
BC	244	33	84	117	2337	410	242	652
Canada	5033	524	328	852	64045	3323	1504	4827

 

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, 24 February to 1 March , 2008 (Week 9)
	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=555]

{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