Influenza activity in Canada continues to increase; ILI consultation rate remains below expected levels
During week 03, influenza activity in Canada continued to increase with more regions reporting localized (n=7; in ON, AB, BC & NT) and sporadic activity (n=22) (see map). The proportion of tests that were positive for influenza continued to increase steadily with a percentage positive of 7.3% (251/3,423) this week (see table). The majority of influenza virus detections to date this season were influenza A viruses (58% or 487/835). In week 03, the ILI consultation rate was 13 ILI consultations per 1,000 patient visits (see ILI graph), which is below the expected range for this week. The sentinel response rate was 62%. In week 03, 4 new influenza outbreaks were reported: 1 in a LTCF and 3 in schools (all from BC).

Antigenic Characterization:
Since 1 September 2008, the NML has antigenically characterized 134 influenza viruses: 30 influenza A/Brisbane/59/2007(H1N1)-like (from BC, AB, ON, NS & PEI), 8 influenza A/Brisbane/10/2007(H3N2)-like (from BC, SK & ON), 5 influenza B/Florida/4/2006-like (from AB & ON) and 91 B/Malaysia/2506/2004-like (from AB, MB, ON, QC & PEI). A/Brisbane/59/2007(H1N1), A/Brisbane/10/2007(H3N2) and B/Florida/4/2006 are the influenza A and influenza B components recommended for the 2008-09 influenza vaccine. B/Malaysia/2506/2004 was the influenza B component for the 2007-2008 season vaccine (see pie chart).

Antiviral Resistance:

Results from the NML:

Since the start of the season, the NML has tested 50 influenza A isolates (28 H1N1 and 22 H3N2) for amantadine resistance. All of the H1N1 isolates were susceptible; however all of the H3N2 isolates were resistant to amantadine (resistance = 100% or 22/22). The resistant isolates were from BC, AB, SK, ON & QC.

The NML has also tested 122 influenza isolates (25 A/H1N1, 11 A/H3N2 & 86 B) for oseltamivir (Tamiflu) resistance. All of the A/H3N2 and B isolates were sensitive; however all of the A/H1N1 isolates were resistant to oseltamivir due to the H274Y mutation (resistance = 100% or 25/25). The resistant isolates were from BC, AB, ON and NS.

All 126 influenza isolates (29 A/H1N1, 11 A/H3N2 & 86 B) tested for zanamivir resistance to date were sensitive to zanamivir.

Oseltamivir resistance findings from Provincial laboratories:

To date this season, 59 influenza isolates in BC have been sub-typed as A/H1 and were assessed genotypically for oseltamivir resistance using an SNP assay. Fifty-four isolates tested positive for the H274Y mutation (resistance = 100% or 54/54), with the other 5 specimens still pending confirmatory testing.

Influenza-associated Paediatric Hospitalizations:
In week 03, 4 laboratory-confirmed influenza-associated paediatric hospitalizations were reported through the Immunization Monitoring Program Active (IMPACT) network. All 4 cases were from Ontario and half were due to influenza A. To date, 31 hospitalizations have been reported of which 68% (21/31) have been due to influenza A. The proportion of cases to date by age group are as follows: 13% were 0-5 month olds; 23% were 6-23 month olds; 10% were 2-4 year-olds; 16% were 5-9 year-olds; and 39% were 10-16 year-olds. The distribution of cases to date by province are as follows: 81% from ON, 10% from AB, 6% from QC and 3% from BC.

*** Over the next several weeks, more retrospective reports of cases may be reported due to technical difficulties with IMPACT's electronic reporting system.

International:

WHO: During the weeks 1-2, the level of overall influenza activity in the world increased, particularly in Europe. In North America and Hong Kong Special Administrative Region of China overall influenza activity remained relatively low.

• WHO

CDC: During week 02, influenza activity continued to slowly increase in the United States. Of the 3,554 specimens tested this week for influenza viruses, 409 (11.5%) were positive. Since 1 October 2008, the CDC has antigenically characterized 207 influenza viruses: 142 influenza A(H1) (all A/Brisbane/59/2007-like), 13 A(H3) (all A/Brisbane/10/2007-like) and 52 influenza B (17 were B/Florida/04/2006-like belonging to the B/Yamagata lineage and the other 35 belonged to the B/Victoria lineage). Since 1 October, 2008, 187 influenza viruses (103 A(H1N1), 23 A (H3N2), and 61 B) have been tested for resistance to neuraminidase inhibitors. Of the A(H1N1) viruses tested, 98% (101/103) were resistant to oseltamivir however all were sensitive to zanamivir. All of the A(H3N2) and B viruses tested were sensitive to both oseltamivir and zanamivir. The CDC tested 126 influenza A viruses (103 H1, 23 H3) for amantadine resistance: only one of the H1N1 viruses was resistant to amantadine (1%, 1/103) however all the H3N2 viruses (100%) were resistant. In week 02, 2 influenza-associated pediatric deaths were reported to CDC (the first cases reported this season to date) .

• CDC

EISS: Influenza activity continued to intensify and progress across Europe with most countries now reporting medium to high intensity. In some western countries influenza activity has already peaked and declined. Influenza A(H3) viruses continue to predominate. With the exception of the few B/Victoria lineage viruses, the viruses circulating in Europe are similar to the strains included in the current influenza vaccine. Of the 115 A(H3N2) isolates that were tested for adamantanes susceptibility, 115 (100%) were resistant. Of the 75 A(H1N1) virus isolates tested for resistance against neuraminidase inhibitors, 73 (97%) were resistant to oseltamivir, but all were sensitive to zanamivir.

• EISS

Human Avian Influenza: Since 24 January 2009, the WHO has reported 4 new cases of human H5N1 avian influenza infection: 3 from China (2 deaths) and 1 from Egypt.

• WHO

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Total number of influenza tests performed and number of positive tests by province/territory of testing laboratory, Canada, 2008-2009

Province of reporting laboratories	Report Period: January 18, 2009 to January 24, 2009				Season to Date: August 24, 2008 to January 24, 2009
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	31	1	0	1	249	1	0	1
PE	6	1	1	2	76	1	2	3
NS	28	0	0	0	351	2	0	2
NB	52	1	8	9	333	6	8	14
QC	1083	60	6	66	10001	151	13	164
ON	1086	36	67	103	12406	103	236	339
MB	48	0	0	0	1046	0	2	2
SK	199	5	0	5	1978	10	0	10
AB	758	22	11	33	10168	114	77	191
BC	132	26	6	32	971	99	10	109
Canada	3423	152	99	251	37579	487	348	835

 

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, 2008-2009 (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, January 18, 2009 to January 24, 2009 (Week 03)
	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, 2008-2009

Percent positive influenza tests, compared to other respiratory viruses, Canada, by reporting week, 2008-2009

Influenza strain characterization, Canada, cumulative, 2008-2009 influenza season by the Respiratory Viruses Section at the National Microbiology Laboratory
[N=134]

{Strain characterization, number identified, per cent of total number}

NACI recommends that the trivalent vaccine for the 2008-2009 season in Canada contain
A/Brisbane/59/2007 (H1N1)-like virus; an A/Brisbane/10/2007 (H3N2)-like virus; and a B/Florida/4/2006-like virus.

Influenza-like illness (ILI) consultation rates, Canada, by report week,
2008-2009 compared to 1996/97 through to 2007/08 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, 2008-2009

Please note that the above graphs may change as late returns come in.

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Definitions for the 2008-2009 season