Overall influenza activity in Canada remains low; localized activity reported in a region in British Columbia
During week 50, influenza activity in Canada remained low overall with the majority of the influenza surveillance regions still reporting no activity. Fifteen regions (in BC, AB, ON & QC ) reported sporadic influenza activity and one region in BC (Fraser) reported localized activity this week (see map). Thirty specimens tested positive for influenza in Canada this week (percentage positive = 1.8%; 30/1,671) (see table). The majority of influenza virus detections to date this season were influenza A viruses (59% or 71/120). In week 50, the ILI consultation rate was 16 ILI consultations per 1,000 patient visits (see ILI graph), and is below the expected range for this week. The sentinel response rate was 61%. One outbreak of influenza was reported in a school in BC this week.

Antigenic Characterization:
Since 1 September 2008, the NML has antigenically characterized 16 influenza viruses: 1 influenza A/Brisbane/59/2007(H1N1)-like (from NS), 2 influenza A/Brisbane/10/2007(H3N2)-like (from BC & ON), 3 influenza B/Florida/4/2006-like (from ON and AB) and 10 B/Malaysia/2506/2004-like (from ON and AB). 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 8 influenza A isolates (3 H1N1 and 5 H3N2) for amantadine resistance. All of the H1N1 isolates were susceptible; however all of the H3N2 isolates were resistant to amantadine (resistance = 100% or 5/5). The resistant isolates were from ON, AB and BC.

The NML has also tested 16 influenza isolates (3 A/H1N1, 2 A/H3N2 & 11 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 3/3). The resistant isolates were from NS and BC.

All 12 influenza isolates (1 A/H1N1, 2 A/H3N2 & 9 B) tested for zanamivir resistance to date were sensitive to zanamivir.

Oseltamivir resistance findings from Provincial laboratories:
To date this season, 19 influenza isolates in BC have been sub-typed as A/H1 and were assessed genotypically for oseltamivir resistance using an SNP assay. Fourteen isolates tested positive for the H274Y mutation, while the other 5 were indeterminate. These specimens were from community-based cases of ILI; none were associated with an outbreak.

Influenza-associated Paediatric Hospitalizations:
No laboratory-confirmed influenza-associated paediatric hospitalizations have been reported through the Immunization Monitoring Program Active (IMPACT) network for the 2008-09 season.

International:

WHO: During the weeks 47 to 48, the level of overall influenza activity in the world remained low with sporadic activity observed in some countries.

• WHO

CDC: During week 49, a low level of influenza activity was reported in the United States. Three states reported local influenza activity however the majority reported either no activity or sporadic activity. Of the 2,585 specimens tested this week for influenza viruses, 72 (2.8%) were positive. Since 1 October 2008, the CDC has antigenically characterized 36 influenza viruses: 20 influenza A(H1) (all A/Brisbane/59/2007-like), 3 A(H3) (all A/Brisbane/10/2007-like) and 13 influenza B (4 were B/Florida/04/2006-like belonging to the B/Yamagata lineage and the other 9 belonged to the B/Victoria lineage). Since 1 October, 2008, 68 influenza viruses (46 A(H1N1), 7 A (H3N2), and 15 B) have been tested for resistance to neuraminidase inhibitors. Of the A(H1N1) viruses tested, 98% (45/46) 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 30 influenza A viruses (25 H1, 5 H3) for amantadine resistance: all of the H1N1 viruses were sensitive to amantadine however all the H3N2 viruses were resistant.

• CDC

EISS: In week 50, influenza activity reached medium intensity in several European countries and has been reported as increasing in several others. There is currently widespread activity in England (UK) and Portugal and outbreaks were reported in France and Spain. Most of the influenza virus detections so far have been for influenza A viruses of which the majority were A(H3). Of the 26 A(H3N2) isolates that were also tested for adamantanes susceptibility, all were resistant. Of the 20 A(H1N1) virus isolates tested for resistance against neuraminidase inhibitors, 19 were resistant to oseltamivir (resistance=95%), but all were sensitive to zanamivir.

• EISS

Human Avian Influenza: Since 12 December 2008, the WHO has reported two new cases of human H5N1 avian influenza infection. The first case was a 19-year-old male from Kendal Province, Cambodia who developed symptoms on 28 November and is currently hospitalized. The second case was a 16-year-old female from Assuit Governorate, Egypt who developed symptoms on 8 December, was hospitalized on 11 December and died on 15 December.

• 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: December 7, 2008 to December 13, 2008				Season to Date: August 24, 2008 to December 13, 2008
	Total # Influenza Tests	# of Positive Tests			Total # Influenza Tests	# of Positive Tests
		Influenza A	Influenza B	Total		Influenza A	Influenza B	Total
NL	21	0	0	0	124	0	0	0
PE	0	0	0	0	38	0	0	0
NS	21	0	0	0	210	1	0	1
NB	27	0	0	0	148	0	0	0
QC	590	3	0	3	5077	34	2	36
ON	254	0	2	2	6134	6	5	11
MB	52	0	0	0	711	0	0	0
SK	111	0	0	0	1118	0	0	0
AB	550	5	12	17	6315	9	41	50
BC	45	8	0	8	498	21	1	22
Canada	1671	16	14	30	20373	71	49	120

 

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, December 7, 2008 to December 13, 2008 (Week 50)
	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=16]

{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 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, 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