Influenza activity in Canada remained similar to previous weeks
During week 06, overall influenza activity in Canada remained fairly similar to previous weeks; however more regions reported widespread (n=3 in BC & ON) and localized influenza activity (n=13 in BC, AB, SK, MB, ON, & NB) this week compared to last week. Thirteen regions reported no activity and 27 reported sporadic activity (see map). In week 06, the percentage of specimens that tested positive for influenza declined slightly to 10% (469/4,531). Of the influenza detections to date, 74% were influenza A and 26% were influenza B (see table). This week, the ILI consultation rate was 23 ILI consultations per 1,000 patient visits (see ILI graph), which is below the expected range for this week. The sentinel response rate was 60%. Twenty five new outbreaks of influenza or ILI were reported this week as follows: 4 LTCFs, 18 schools, 1 hospital and 2 other.

Antigenic Characterization:
The National Microbiology Laboratory (NML) has characterized 370 influenza viruses for the 2007-2008 influenza season: 223 A(H1N1), 37 A(H3N2) and 110 B viruses. All influenza A(H1N1) viruses were antigenically similar to A/Solomon Islands/3/2006. Of the 37 influenza A(H3N2) viruses characterized, 5 were antigenically similar to A/Wisconsin/67/2005 and 32 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 110 influenza B isolates characterized, 3 were antigenically similar to B/Malaysia/2506/2004 and 107 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 281 influenza A isolates (228 H1N1 and 53 H3N2) for amantadine resistance and found that 51 (96.2%) of the 53 H3N2 isolates were resistant to amantadine and 4 (1.8%) of 228 H1N1 isolates were resistant (see recommendation from the 2006-2007 influenza season below).
The NML has also tested 299 influenza isolates (192 A/H1N1, 30 A/H3N2 & 77 B) for oseltamivir (Tamiflu) resistance and found that 16 (8.3%) of the 192 H1N1 isolates tested were resistant to oseltamivir.
The resistant isolates were from NL (2), ON (11), MB (1) and BC (2). Nine resistant isolates were collected in December 2007 and 7 were collected in January 2008. These oseltamivir resistant strains remain sensitive to the antiviral amantadine. While antivirals can be used to lessen the length and severity of influenza, vaccination remains the most effective method of preventing illness. This year's influenza vaccine protects against influenza A(H1N1) and therefore vaccination remains an effective measure in preventing illness.

Influenza-associated Paediatric Hospitalizations:
No new laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network this week.

International:

WHO: During weeks 4–5, the level of overall influenza activity in the world increased. A considerable increase in both influenza activity and the number of viruses detected was observed in most countries of Northern Europe and North America, where mostly influenza A (H1N1) circulated, as well as A (H3N2) and B viruses.

• WHO

CDC: During week 05, influenza activity continued to increase in the United States. The proportion of specimens that tested positive for influenza virus increased to 23.9% this week. Since September 30, 2007, CDC antigenically characterized 197 influenza viruses: 101 influenza A(H1) (97 A/Solomon Islands/3/2006-like and 4 showed somewhat reduced titers with antisera produced against A/Solomon Islands), 53 influenza A(H3) (6 A/Wisconsin/67/2005-like and 46 A/Brisbane/10/2007-like, and 1 showed somewhat reduced titers with antisera produced against A/Wisconsin and A/Brisbane), and 43 influenza B viruses (3 belonging to the B/Victoria and 40 B/Yamagata lineage). Small numbers of influenza viruses resistant to oseltamivir have been detected in the United States, representing 4.5% (15/331) of all influenza viruses tested (8.1% among H1N1 viruses tested).

• CDC

EISS: In week 06, medium levels of influenza activity were reported in most European countries. A significant proportion (20.5%) of the A(H1N1) viruses circulating in Europe were resistant to oseltamivir with resistant viruses found in 13 European countries.

• EISS

Human Avian Influenza: Since 9 February 2008, the WHO reported 2 additional cases of H5N1 avian influenza infection: 1 from Indonesia and 1 from Viet Nam (fatal).

• 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 3 to February 9, 2008				Season to Date: August 26, 2007 to February 9, 2008
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	82	7	8	15	376	32	14	46
PE	2	0	1	1	44	0	2	2
NS	26	1	1	2	304	3	3	6
NB	49	2	6	8	351	4	10	14
QC	1276	102	17	119	10651	331	53	384
ON	1258	45	12	57	14908	769	50	819
MB	75	2	2	4	1621	13	6	19
SK	215	16	4	20	2863	95	50	145
AB	1343	100	83	183	16649	384	414	798
BC	205	37	23	60	1731	287	78	365
Canada	4531	312	157	469	49498	1918	680	2598

 

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, 3 February to 9 February , 2008 (Week 6)
	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=370]

{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